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https://www.decware.com/cgi-bin/yabb22/YaBB.pl AUDIO FORUMS >> General Discussion and Support >> Inherent Hum of Zen Amps + 105 dB Efficiency https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1708290398 Message started by mk60 on 02/18/24 at 21:06:38 |
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Title: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/18/24 at 21:06:38 Hi all, I have a set of Klipsch La Scala AL5 speakers (nominally rated at 105 dB efficiency, IRL probably lower), and a couple of different Decware triode amp based setups. I feel like I've discovered that Decware's amps might not be a great fit for speakers this efficient, and I wanted to get some feedback on the community from this before I jump to conclusions and totally re-think my setup. Also, if my findings are generally correct, this post could also act as a PSA for people to think hard before chasing Decware amps to pair with very high efficiency speakers. I'll first say that when I first got my La Scalas which were my dream speaker at the time, I did research and found that many people were saying that it's a no-brainer to pair high-efficiency speakers like this with good low power SET amps -- a perfect match. This is around the time that Decware's wait list really started to blow up (thanks partly to Andrew Robinson, who highly sung the praise of the SE84UFO with his La Scala AL5s). I decided to jump in and see what the fuss was about. Since then I've been able to get my hands on two different Decware amps to pair with my La Scalas, with limited success. 1) A pair of SE84UFO25s, which I have run in three different configurations: a) just normal stereo from a single amp, b) unbalanced dual mono, and c) fully differential balanced mono (in this case fed balanced signal from a ZTPRE) 2) SEWE300B (just arrived last week!) running in standard stereo operation without any pre-amp. I'll start by saying that everything that everyone has said about how nice these amps sound is true, they're lovely. But in nearly all cases, I'm getting what I think is an untenably loud 60 Hz hum from my speakers and subs -- this hum is about 46 dB at my listening position, about 10 feet from my speakers. While this isn't noticeable when playing many different genres of music at sufficient SPL, it is ever present in quiet moments, and for example when listening to classical music (either solo piano or larger orchestral works) instruments fade into the 60 Hz hum instead of into silence which I think really hurts the music. Of course, I've done research on these forums and there are many threads about hum and how to, in some cases, eliminate it. I've also had the pleasure of having a few long phone conversations with Steve about it, what my expectations should be, and how to troubleshoot it. Often, hum is attributed to ground loops in your signal chain, and many people are able to substantially reduce and solve hum in their setup by figuring out which components are causing the ground loops, using DC blockers, etc etc. Based on my testing, I do not believe that I have any ground loop issues, or at least, by far the main contribution to the hum is not from ground loops. This belief is based on the fact that with any of the three amps (either of the UFO25s or the 300B), if I unplug absolutely everything from all outlets in the room, only plug the amp into an outlet, and then connect a speaker, the hum is there. It is completely unaffected by whether or not any input is connected to the amp, completely unaffected by whether or not I plug other things into other outlets, and is also completely unaffected by the volume knob on the amp -- it hums just as loud at zero gain as it does at full gain. In my conversations with Steve, I explained my situation, and he explained that there is definitely inherent hum in these amps that is part of the nature of the design. He very carefully voices his amps and has specific design targets in mind when he does so, and although he could completely eliminate the hum, the amp wouldn't sound the way he wants it to if he did so. He said (and I may be misquoting here, sorry if I get this wrong, Steve) that he designs it such that when using ~100dB efficient speakers, whatever inherent hum exists is negligible/unnoticeable at a normal listening position, but detectable if you go right up the driver. Unfortunately, with my La Scalas, that is far from the case. The conclusion that we seemed to get to in our conversations was that the hum I'm experiencing is inescapable if I'm going to pair speakers this efficient with these amps. This is a bummer. There's so much I like about the sound of my UFO25s and of the SEWE300B, but it honestly makes it hard to listen to certain genres of music (e.g. classical music with high dynamic range) without being bothered, and it also makes it that having the amp on in the background playing music at a social gathering is annoying, because the hum is constant and totally noticeable by everyone in the room. There is only one situation in which there is no hum: running the pair UFO25s in differential balanced mono. This isn't a full solution, though, as it prevents me from hooking up my REL 212/sx subs using high level connections, which is frustrating (have confirmed this with Steve). But it really gives me a taste for how good these amps can be, and it really motivates me to see if there is any way to enjoy my SEWE300B without the hum ruining it for me. What I would like to ask is whether anyone else has had any similar experiences, and have figured out a way to fix it? I guess I'm specifically asking people who have paired Decware UFO or 300B amps with La Scalas or similarly efficient speakers without having audible 60 Hz hum at listening position? I'm holding out some sliver of hope that perhaps I misinterpreted or misunderstood aspects of my discussions with Steve when I was troubleshooting, and there is a way forward! And if not, I really would like to have my experience serve as a warning to people who are on the waiting list for one of these amps to pair it with a pair of La Scalas or Klipschorns, because if this is really an unfixable issue, these people might end up disappointed with their purchase. One thing that gives me hope that there's a way forward here is that Andrew Robinson gushed about the pairing of his La Scalas with his SE84UFO, and I have a really hard time believing that he would have done so if he was getting the same loudness of hum that I am, or at least would have mentioned it as a caveat if he did. I hope that I've faithfully represented my experience and the content of my discussions with Steve, but am happy to clarify further, or hear clarifications from Steve or anyone else if not! It's always been a delight chatting with Steve about this, and I think he makes great amps, and I hope my post does not come off as an accusation of false advertising in any sense on his part. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/18/24 at 21:32:50 (oh and yes I have dialed in the hum knobs on the SEWE300B! the knobs are set at the obvious point where hum is minimized) |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 02/18/24 at 21:35:43 Quote:
46 dB hum at the listening position would indeed be a problem, I feel your pain. I have a pair of UFO25s, configured as balanced monos, and they are dead quiet. Like heat death of the universe quiet. I have 95 dB speakers, but I feel like I could certainly hear 56 dB hum if it were present. The same holds true for the UFOs I had previously. Quote:
This is interesting. If feel like if you aren't getting hum with balanced mono, then the hum isn't inherent in the amps themselves. Did Steve have an opinion on that? To me it sounds like you are picking up noise, maybe RFI, that is canceled out with balanced. Quote:
What if you connect the amp like it is balanced? I.e. connect the left and right positives to the speakers and short the negatives. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/18/24 at 21:52:23 Quote:
Yeah, I definitely agree that in differential mono, they are dead quiet! Quote:
I may be misremembering, but his reaction seemed to be more along the lines of "oh, well that's good news" rather than it standing out as strange? But yeah, I would be really interested to know if this is indicative of an external noise source that I could eliminate to be able to run quietly without balanced! Quote:
Dead quiet :) Then if you remove the short and connect the speaker in the traditional way, boom: hum. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 02/18/24 at 22:15:57 How long are your speaker cables? Sometimes they can act like an antenna can collect RFI. And that is a problem that balanced fixes. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by cmdc on 02/18/24 at 22:21:40 I use Zu Druid Mk V speakers (101 db) with both a UFO25 and a ZMA. I can detect a very soft hum if I’m standing right next to the driver, but it’s inaudible from my listening position 8 feet away, even if no music is playing. In the instances where I’ve encountered a hum loud enough to be disruptive, I’ve usually (and typically after a lot of work) traced the problem to touching interconnects or to often subtle problems with how the speaker cables were positioned. Since the problem appears to be source independent, you might want to experiment with adjusting the speaker cables. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/18/24 at 22:36:59 Quote:
Long! 15 ft and 35 ft due to where equipment is vs speakers. I know this isn't ideal, and shorter runs are better, but it was never obvious to me that it could cause this big an issue. I've got some speaker cable I can experiment with by making a short run and comparing. The high level cables feeding my subs are I think ~30 ft and are the standard ones that REL supplies in the box. Interesting food for thought in Andrew Robinson's La Scala AL5 review: he goes out of his way to make the point that due to the La Scala's efficiency, some amps aren't a great pairing because they're inherently noisier and the high efficiency of the La Scala's amplifies that in a way that might be unbearable. He suggested for example that pairing with the Naim Uniti Atom (which I also have) produces undesirable hiss and isn't a great match. On the other hand he says that the SE84UFO2 is a perfect match. The hum I get from my UFO25s on my La Scala's is way worse than any background noise/hiss I hear when I connect the Naim to my La Scala's, suggesting that somehow he didn't get any noticeable hum from his UFO2 (otherwise he very likely would have mentioned it). |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/18/24 at 22:49:42 Okay I made a 1 ft cable and tested it on a single UFO25 vs 15 ft -- same amount of hum :/ These are good suggestions though! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by MikeinMontana on 02/19/24 at 00:03:37 We've had our Klipsch chorus II's since 1998. They are listed as 101 db, 1 watt/1 meter. We have had very low or even zero hum hooked up to our Zen UFO amp. Have to have our heads right next to the drivers of the speakers. And that's with no music source playing , or even when extremely low in sound level. 3 feet away, no apparent hum at all/ all sound levels.. So not sure it's a sensitivity problem. At least not in our case~ Have great evening~ Mike edit: I remembered we used to have some hum due to our sub. a 3 prong plug adapter to a two prong cleaned that right up. In fact..it's still hooked up that way after having it since 2007. It's an HSU vtf-3. The original front firing version. It was mentioned in the manual to use the supplied adapter if needed. Your amount of hum would drive me nuts. I hope it gets figured out. Such amazing sounding amps |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/19/24 at 01:20:36 Thanks Mike! Yeah I've actually tried a fancy version of that kind of adapter that someone else suggested in a hum-related thread elsewhere on the forum, but it made absolutely no change :( as seen here https://www.amazon.com/dp/B08XWHJRZ1?psc=1&ref=ppx_yo2ov_dt_b_product_details More food for thought: one thing I don't currently understand here is, if you take seriously that the reason that I'm getting unreasonable hum is due to the inherently high efficiency of my main loudspeakers, what of my subwoofers? I'm running a stereo pair of REL 212/SX subs connected via high-level speak-on connection. The 60 Hz hum coming from the subwoofers is actually even a little louder than the hum coming from just the speakers! Are my subs "high efficiency" too? Is that even a sensible thing to say about an active sub? I wonder if this is any evidence that the problem is not just the efficiency of my mains. If anyone has used a REL 212/SX with their zen amp over high-level connection please do chime in about hum! Again thanks to anyone willing to think about and workshop this! :) |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Chester on 02/19/24 at 02:49:23 You may have discussed or tried this, but I remember having a hum on my Zen amp 25th and receiving advice about using a grounding wire from a speaker terminal to the transformer and the hum disappeared. I’ll confirm the wiring when I get back home, but maybe someone else can confirm this “solution” in the meantime. Best of luck! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by will on 02/19/24 at 15:06:34 I remember Chester's idea working for folks too... can't recall the setup either though. Seems like Steve suggested trying it for a Rachel if I am remembering correctly. That all three amps hum with nothing plugged into them, it is likely not tubes, and all amps acting similarly, likely not a build fault... a DC blocker does not help (different than the ground lifter Mike was talking about that solved his sub hum)....and short speaker cables don't help... Also, seems there are enough folks with high efficiency speakers who have not had this level of hum including the reviewer you talk about with your speakers (I could not handle 46 dB 10 feet away either). But set up as balanced monos does work...this all makes me imagine you have a room and/or house noise issue that Decware shows up. Here, in the high desert, it gets so dry at times, that watering my house ground rod area with a slow seeping flow helps when I notice hum. I wonder if you have tried different circuits in your house? Is there another room/circuit you can reach with your 15 foot speaker cables? Or maybe try a heavy duty extension cord. I guess you tried different power cables. Is anything else hummy in your house? I wonder if your house ground is not performing up to snuff... Also I wonder if there is a balanced transformer you can easily get your hands on that you could test before the amps. I find hum issues confounding and for me, 60 and 120 Hz hums are really irritating... sorry you are experiencing this! The subs using speaker level connections will be receiving the same signal as the La Scalas right??? And are using the same power. Good Luck! Will |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 02/19/24 at 15:47:27 Quote:
I feel like this is the clue, but I'm not smart enough to figure it out. Since the hum is there without any input, or with very short speaker cables it is clearly coming from the amp. And since differencing the L and R channels removes it, it is the same in both channels. Very frustrating. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/19/24 at 19:28:31 Quote:
So, I would push back slightly in that the reviewer is the only person I'm aware of who has given a positive review (or any review at all) of a Zen amp using speakers of a sensitivity this high. The highest sensitivity of anyone reporting in this thread so far has been 101 dB, which is still quite a bit lower than 105 dB. I guess all I'm trying to point out here is that Andrew Robinson's data point is the only one I've seen so far that suggests that 105 dB efficiency can work well with a zen amp. Quote:
I believe that the suggestion you're referring to is to short the two negative terminals together, or to short a negative terminal to the transformer. I have confirmed with Steve that shorting the two negative terminals is only okay to do when running one of these amps in standard stereo operation. Back when I was running a single SE84UFO25 in stereo, I actually did find this trick helpful. It did not eliminate the hum, but it did reduce it to a level that was almost tenable and much better in comparison to without that trick. I actually also found that this helped with hum when running my SE84UFO25s in standard non-balanced mono, but it actually created other issues that I eventually talked to Steve about and he pointed out that one should not be shorting those two terminals in non-balanced mono operation. Thread about it here: https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1695958380 Unfortunately, for the SEWE300B (which is really the thing I want to focus on getting to work here), shorting the two negative terminals does absolutely nothing for the hum, and neither does shorting a negative terminal to any point on the output transformer (screw or shielding). If the shorting of the two negative terminals worked as well for the SEWE300B as it did for a single SE84UFO25, I might almost be in business with the SEWE300B. Alas. Quote:
Thanks for the suggestions, Will! If the issue is somehow with the power/grounding in my home, and it is fixable, that would honestly be the ideal situation. I'll say that as far as moisture goes, it's very rainy here right now :p My room is 30 ft x 12 ft, and my la scalas are at the far end, making them 30 ft from any other room in the house. I have tried 6 different outlets in this room with the same results, but I don't know anything about the wiring/circuits of my home to be able to say if I've tried different circuits. Perhaps it couldn't hurt to have an electrician come take a look and teach me about how my home is set up, electrically. If anyone has a recommendation in LA I'd totally look into it! Re: your suggestion about a balanced transformer, I would definitely try it if anyone has a recommendation for a specific one I can grab used on usaudiomart and re-sell if it doesn't help! Quote:
Right, this does help suggest, I think, that the La Scalas may not be the issue, as it should be reasonable to use powered high-level connected subs on these amps without insufferable hum, regardless of what loudspeakers you're using.. at least I would hope so. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/19/24 at 19:46:05 I'll also add that in our previous discussions of hum, it really did sound like Steve thought that this was just a speaker efficiency problem and was the nature of the beast, and it didn't sound like he thought that hunting down electrical issues or trying power conditioners etc would help. But I guess I'm not totally sure that I conveyed to him just how loud the hum is. Would be curious to hear what he thinks of this discussion, and I might try to schedule another call to discuss my SEWE300B now that it's here and humming louder than ever. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by will on 02/19/24 at 21:22:51 mk60, I am just thinking out loud here, hoping to help... but I am no expert on hum... And I could easily be wrong, but I am having a difficult time thinking Steve would attribute 46 dB 10 feet from the speakers entirely to the high sensitivity! Also, does Steve know you got sweet quiet with the 25ths set up as balanced monos? I would be inclined to call again if you feel like you may not have told him the whole story... with luck this might give him ideas??? When hum has been bad here, like with my "new" 300B amp that has no volume, it was ground loops, and I fixed it by plugging all the main stuff into the same conditioner. Interestingly, I had some pretty low key and tolerable hum before rewiring things using my Torii, but it is a different design, and has an attenuator... not cranked all the way. The 300b hummed badly though, and like you, my first thought was that the amp was defective somehow. I finally found plugging all in together mostly solved it, but did discover some of it was the CSP3 and ZRock2 by taking them out of the loop, and going directly from source, through the ZBit, and into the 300B... That was super quiet. But for me, it was quiet enough with the active pre stages, some hum heard near the speakers. I do not have super high efficiency speakers though, mine being rated at 92-92.5, and 94 db. This being a hard place to get good ground, my experience with that is just experiential, not really understanding all the nuances of grounding, but knowing it was ground related. I also recall when I first moved here, I snugged up all the circuit breaker connections, and some were pretty slack, and tightening them improved the sound... Can't recall the details, but it was better. Mainly just pointing to how bad wiring, and/or a weak ground in the house or room can effect these things... Then there is other noise. I have a slight hum with the 300B/845 amp I am using now. And if the amp did not have a volume (run wide open) the hum would be a little too loud for me. But running it with the ZBit and CSP3 in front, and tuning the gains between the three for best sound, the amp's volume knob is usually between 9 and 12 o'clock, and it is all pretty quiet, hearing it near the drivers but not at the seat. So I have not opened it to check bias and adjust hum pots. But when my boiler cuts on, the boiler on a separate circuit, I hear more hum from my speakers. I also get a little more hum at times that appears to be from neighborhood use being higher/noisier... so noise in audio is weird stuff! With this amp, the hum actually gets a little quieter when ICs hook it to my CSP3... Also.... I don't know whether a balanced transformer would fix it, just recall that some people have some improvement with them in cancelling at least some house power noise. Also there are a lot of folks who give a load of praise for the nicer Puritan Audio conditioners, and I am pretty sure they even make some kind of rig that allows adding a separate ground for the audio system... don't remember details, just thinking it may become worth it to read about these or ask a dealer. But if you can get a creative electrician in, who is tuned into these things, and you want to learn about your wiring anyway... it may be a good trouble shooting and learning opportunity, especially if talking again with Steve causes you to think this is a good idea. I know LA is giant, but isn't Upscale Audio in the area... If it seems relevant to you, they may just know some electricians who are a little outside the box in ways audio heads need who is nearby? Good Luck! Will |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Kahuna Jack on 02/19/24 at 22:46:58 Just curious , It looks like you also have a Rachael , have you swapped that amp in directly and observed hum level ?? |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/20/24 at 00:23:11 Quote:
I appreciate your willingness to spend your time sharing your thoughts!! Indeed a call to Steve with a more complete picture of my experiences may be worthwhile. I felt a little bad bothering him as much as I did since my UFO25s were bought used, but I did just buy the 300B from him so hopefully another phone call isn't an overreach :p Quote:
Yes, actually. There is hum from my La Scalas is very little when paired with the 34I.5 - basically inaudible at listening position. If my 300B or UFO25s were this quiet I would be thrilled. I don't know if this difference is suspect, though. These are all different designs, and Steve did say to me that the inherent hum from the 300B is definitely louder than that from, say, the UFO25s, and that is just inherent to the design. My guess is that the SE34I.5 is just inherently quieter from a hum standpoint. I actually have experimented a little further, and realized that I was using my dB meter wrong. It turns out that I was using A weighting, which, at this low of a frequency of sound was not picking up very audible differences between different hum levels. Switched it to C weighting and it seemed to reflect the differences between loud and soft hums correctly. The result, though, is that the hum is actually much worse than my originally reported 46-47 dB at listening position. Using C weighting it is actually almost 59 dB! I did some controlled tests with the SEWE300B to give us more information and troubleshoot. I brought my Zu Audio Dirty Weekend 6s into my listening room and set them up next to the La Scalas. The Zus are 95 dB efficient. They're a couple feet closer to the listening position but I don't think that should change much of the conclusion from the numbers measured. dB meter was in exact same place for all tests with C weighting on. I took turns measuring hum from my Zus, La Scalas, and subs, as well as subs together with either set of loudspeakers: La Scalas alone: 58.7 dB Zus alone: 49 dB Subs alone: 53.3 dB La Scalas + subs: 59.1 dB Zus + subs: 50.6 dB (interestingly less than the subs alone, my bet is that the placement of the Zus relative to subs made some cancellation) I would call the hum from the Zus alone barely audible from listening position, acceptable on their own, but starting to cross the line once the subs are in play. The La Scalas are clearly the main contributors to the loudness of the hum, but still, the subs aren't doing great either. Finally, just to double check whether speaker cables are an issue, I swapped the Zus between the long amazon cables I had been using for the La Scalas, and a nice short (6 ft) set of Zu cables that connect to the Zu speakers via proprietary connector, and hum was the same in either case. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/20/24 at 00:56:12 One final observation: the hum from the SEWE300B, when the hum knobs on the amp are optimized, actually appears to be 120 Hz, not 60 Hz. When the hum knobs on the amp are moved from their optimized positions, interestingly, 60 Hz hum seems to get imposed on top of the baseline 120 Hz hum. Anyway, problem in principle seems to be the same? |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 02/20/24 at 01:25:01 Quote:
Not really. The 60 Hz hum in the 300B amp comes from the 60 Hz AC that is used for the filaments in the 300B tubes. When it isn't balanced (by the pot) you get hum. All the other amps use DC for the filaments, so it isn't an issue. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sean on 02/20/24 at 02:24:42 The only useful info I can add is I use Tekton Pendragons 96db and a UFO. With the UFO at 9 out of 10 on the volume I get an audible hum in my seat. I generally listen between 1/2 and 3/4 so it doesn’t bother me. Ear next to speaker, I can hear hum starting about 2/3 volume. I don’t hear that in my seat or it would drive me absolutely bananas. I hope you find a solution soon. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Paul2 on 02/20/24 at 14:20:01 This is a subject that I have direct experience with. I have a pair of La Scala speakers. They are around forty years of age. They are using the ALK crossovers. The La Scala's have been in my house for over twenty years. Over this long term we have used many different amplifiers, SE84's, Pentode, SET34, Push Pull EL34, SET 300B and SS amps. NEVER, have we experienced HUM ! For me hum is totally unacceptable. Yes, Klipsch Heritage speakers are/can be very transparent and will bring out any flaws due to their efficiency. You either enjoy the Heritage sound or you don't. I love them ! In my room we rarely ever listen at over 80db. But even when putting me ear up to the horns, I never hear any hum. We also have five other types of speakers that get rotated into the mix from time to time. I find that each of these speakers have their own sound. They are like children, each have their own personality. In this respect I am blessed ! I truly feel your pain. I wish I had a solution for what your experiencing. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/20/24 at 15:04:26 Quote:
Thanks for chiming in! :) I'm wondering if you happen to know what the sensitivity / efficiency spec for vintage La Scalas is? I wonder if it has changed in the modern ones or has stayed the same over the years. Also, the loudness of my hum is totally independent of the gain setting, so, it actually makes low level listening worse :( |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by MikeinMontana on 02/20/24 at 16:48:23 I have collected Klipsch literature and pamphlets/brochures etc over a lot of years. This an older one, probably the Early 80's. Klipsch fans from since kids~ I hope this gets ironed out mk60 |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/20/24 at 16:55:16 Thanks Mike, looks like it's about the same at 104 dB. Will be chatting with Steve either today or Thursday, let's see what he thinks! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/20/24 at 17:51:37 I just spoke to Steve and gave him the rundown of my situation and tests, and he agreed that although there is inherent hum in all of these amps (the 300B a few dB moreso than the UFO25), it should definitely not be near this loud either for my La Scalas or for my Zu DW6s, and there seems to be an independent issue here. His recommendation was to test my outlets and/or get an electrician to come and check out my wiring. The house I rent is very old, and although very charming, based on the quality of the construction itself it would not surprise me whatsoever to learn that the way the home is wired isn't 100% correct. I'll update! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 02/20/24 at 18:05:40 Quote:
I think one option that was suggested earlier was to get a balanced isolation transformer. I'm kinda surprised Steve didn't recommend that, he as before on the message board. There are a bunch of options, Decware makes one: https://www.decwareproducts.com/zlc I got mine from ebay, aka China or you can try these guys: https://toroid.com/ FWIW I tried buying from them before ebay, but the wait was too long. The transformer would isolate you from noise and/or DC on the mains power, but I'm assuming there is a class of problems that would require professional intervention. Full disclosure, my knowledge of home electrical is largely theoretical so JMO, YMMV and all that. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Kahuna Jack on 02/20/24 at 18:11:35 "The house I rent is very old, and although very charming, based on the quality of the construction itself it would not surprise me whatsoever to learn that the way the home is wired isn't 100% correct" Except the Rachael operates fine . Maybe start all over and start swapping cables,speaker wire ,power cords etc etc one at a time and see if you can achieve a ground zero free of hum. Frustration Im sure but a Sarah , 2 ufo25's and a Racheal is a problem alot of folks would LOVE to have ! Hopefully it will be something simple and overlooked . Good luck |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/20/24 at 18:35:03 Quote:
Yeah I think I'm going to try this, gonna look for a used one that I can easily re-sell without a loss if it doesn't help. Quote:
Yes, true. But as mentioned before, all of these amps are designed differently and will have different levels of inherent hum. My understanding is that 300B > UFO25 > Rachael in terms of internal hum, and I guess the theory is that whatever problem I have going on raises the hum level of all three, but the Rachael having less internal hum than the other two means it's still not bad even with whatever issue I have. I also have had other tube amps in this home that don't hum at all. In any case, your suggestion could still be worthwhile :) |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by LiquidBlue on 02/20/24 at 21:27:54 I’m not sure if this will be helpful to you or not, but I have been having a similar issue and have spent the past few weeks troubleshooting. I also live in the LA area and am in an older home with older wiring. My speakers however are lower sensitivity, at around 93-94db. It seems that since the heavy rains a few weeks ago, I started having a buzzing sound from my speakers that was audible in my listening position. It seems to be a 120hz hum, but sounds more like buzzing and is there even when all of my gear is turned off. Sometimes is clearly audible, while others it seems slightly subdued, but always still there. When I turn the amps on I get the common dull hum that is only evident when my ear is to the speaker, but the 120hz buzz is audible from my seat. In time I isolated the issue to my REL sub (which I only connect with high level connection using the REL Speakon connector). I tried moving cables around and changing power cables, etc. but no change. Last week I had a chat with Steve and also with Jacob at REL. Both gave some things to try with respect to how the sub was connected, speaker/jumper connections to better ground the gear, etc. Nothing seemed to work until this morning. Of course, it was the very last thing left to try from Jacobs suggestions! It’s not a good fix for me at the moment, because it involves a lot of rearranging, but at least I know the issue and what will fix it. My REL is set up on the other side of the room from my audio components. I have three outlets along the front wall. On the left is the outlet for the two channel system. In the center is my home theater setup and TV and to the right is my REL sub. This morning I moved the sub and plugged it in to the same power distribution unit that the rest of the audio gear is plugged into and this totally fixed it. I want to see if there is another solution, than to have to rearrange my living space or run a long extension cable for the sub, but I also recently found out the center outlet for the HT has a ground fault, so I will have a chat with an electrician friend to see what he may suggest. If you have gear plugged into a different outlet, try plugging everything into a common outlet/strip to see if that helps. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/20/24 at 23:19:09 Well, the good news is that a local electrician was able to come by today, but the bad news is that they said everything looks good and there are no issues with the house's wiring or grounding. He looked at the breaker panel, found where the actual ground rod is, and said everything looked fine. Tested one outlet, said everything looked good. This leaves me in a tough spot. Steve seems sure the problem is not the amp, electrician seems sure the problem's not the wiring.. what else is there? One desperate idea I have: I can bring the 300B to a local hifi space where they've got La Scalas set up, and see if we get the dreaded hum there. Quote:
Thanks for describing your situation! Sounds like you had a ground loop. Unfortunately, the hum is the same even if literally the only thing plugged in to any outlet in the room is the amplifier. Also tried plugging everything into the same powerstrip etc. I do really wish it were a ground loop! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Kamran on 02/21/24 at 00:48:35 Maybe you did this already, but was wondering if you tried different 300B pairs to gauge if the hum is impacted? |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/21/24 at 00:55:04 Quote:
I have not, I only have a single new pair of WE 300Bs that I bought with the amp. But based on the fact that my two different UFO25s hum almost as much as the 300B amp, though, even if a different pair of 300Bs did reduce the hum a bit, it would be unlikely to reduce to listenable level :/ also, the hum is identical in either channel, so both would have to be defective in the same way for that to be the issue? |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Gilf on 02/21/24 at 01:08:30 I had a similar hum issue develop last year and thought it was an amp problem because nothing else had changed. Tried several sets of tubes- all the same hum problem. Come to find out it was the power cord connection got fussy when I disconnected and re-connected it. New cord, dead silent. Will has some sage advice. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/21/24 at 01:30:49 Quote:
I'll definitely try a balanced transformer if I can get my hands on one :) I did call Upscale to ask about electricians but they just said they don't know anybody lol [smiley=icqlite19.png] also tried many power cords and many outlets, with no change. but with everything that's ruled out, hopefully we get closer! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Kamran on 02/21/24 at 02:40:41 Not surprised that Upscale didn’t recommend any electricians. I recall calling three different dealers prior to installing my dedicated lines and nobody would recommend an electrician—-perhaps to do with liability issues? That said, if you do want to consult an audiophile electrician, I’ve heard good things about KingRex Electric (don’t hold me to it, but I think he’s based in TX and he worked on bettering Michael Fremmer’s electrical system)—he also does phone consultations based on looking at pictures of your panel. Just a thought….if you wanted to investigate the electrical issue further: https://www.kingrexelectric.com/about Now on to Hum/Noise to provide more context on my earlier post: Was using WE and was getting noise (not Hum) from both channels in Jan…tried the hum pot, checked the grounding, tried plugging everything in to one outlet, changed all the tubes except the WE. Like what are the chances of both WE tubes being bad—-absurdly low right? Yet, as soon as I reinserted the stock Chinese tubes, the noise was gone. My situation with WE is on-going. They accepted one tube as bad, but didn’t change the other one. I subsequently heard noise on the one they didn’t replace, shot video proof and sent it back last week. Still waiting to hear back. I have tried 3 different tubes on my Sarah and the amount of hum (or lack thereof) is equal between the pairs. The Chinese tubes are deadly silent—in fact, they have been even quieter for the past two days, leading me to think there was something wrong with the amp. The WE (when working properly) had very very very faint hum…I actually wouldn’t even call it hum, it just felt the tubes were just energized to give off sonic pleasure. Not at all a showstopper, like in your case. There is a third pair I tried, that had a very disconcerting level of hum—equal from both channels, yet they tested just fine. The hum pot didn’t fix it. That was a showstopper. Not necessarily saying the tubes are the issue in your case—just that don’t discount their impact. Hope you get to the bottom of it soon! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/21/24 at 03:10:34 Thanks, Kamran!! KingRex looks really promising :) I'll reach out to him tomorrow. The electrician that came by today was pretty quick about it, maybe a bit dismissive, and was a bit hesitant to bother testing my outlets after looking at the panel and ground pole -- seemed a bit incredulous that I called him out there to begin with. Sounds like KingRex will at least be patient in thinking about it. As for the tubes, that's pretty interesting! And it's annoying to hear that WE didn't take both tubes back. It couldn't hurt to try a cheap pair of chinese 300Bs. I actually just tried configuring the SEWE300B in differential mono and the hum totally dropped to a very very faint background noise, so that might be what you're talking about :) Difference between single speaker hooked up to amp in normal stereo vs differential mono was 10 dB! Not a surprising data point though, given my experience with the UFO25. At this point, if it were possible for me to get a second SEWE300B to run differential.. I'd consider it lol. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by will on 02/21/24 at 12:50:41 I agree with your ideas about the electrician. It seems pretty well known that is takes an unusually thoughtful and interested one to "get" how sensitive audio is to noise. And checking only one receptacle.... I hope Kamran's kingrex tip pays off! It is weird to me though that there is that big of a difference between the SE34 and the 300b, and SE84s especially... Sure, they are different designs, and those differences might be tweaked by your particular room and/or house power, but Steve tries to make them all quiet enough for most people. Speaking of tubes, I wonder if you have tried rolling the inputs and rectifier from the SE34, one position at a time, into the driver and rectifier positions of the 300B...and same into the input and rectifier positions in one of the SE84s? May not solve it, but it might be worth it to see if there is any change, especially a lot of new rectifiers can go off. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by thevinoman on 02/21/24 at 14:53:07 Considering everything you've done so far, (and I might have missed this in this long thread), I guess the first thing I'd do is to run a completely separate line from your breaker panel to a new outlet. Sorry that you don't have a very interested local electrician, but perhaps you need to find someone else who can physically come to your place and put a bit more effort into helping you. Dealing with old houses and their systems can be a nightmare sometimes. Getting the isolation transformer should certainly point you in the right direction to hopefully getting some resolution. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/21/24 at 17:15:34 Quote:
I am also surprised that the SE34 is markedly quieter than the SE84, but again I have two SE84UFO25s that were built at totally different times that are acting identically, which are much louder than the SE34. I would say the SEWE300B is about 2-3 dB louder than the UFO25s, but the UFO25s are *much* louder than the SE34. I will try switching the tubes between the UFO25s and 300B! One other interesting data point regarding the difference in hum levels of different models: I spoke to someone over on the Klipsch forums who said that they had no hum at all running their SE84UFO2 on his Klipschorns (same sensitivity as La Scala). Interestingly, SE84UFO2 is also the model that Andrew Robinson tested on his La Scalas. Now beginning to wonder if the hum level of the SE84UFO2 is closer to the SE34I.5 than it is to the UFO25... maybe another question for Steve. Quote:
I rent this house, so, outright modifications to the wiring will be a hard sell, unfortunately. What the electrician did say is that despite the age of the house, the wiring does look pretty modern and current. When you say isolation transformer, do you mean balanced transformer? When I look up all these different kind of transformers they all have different names and I really can't tell how they're different and exactly what I shuold be looking for :/ One new thing I get to try today that both Steve and Rex have suggested to try: "lifting" the ground. Have a 3->2 prong adapter coming from amazon today. Not a safe solution long term, but should hopefully give information about the problem! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 02/21/24 at 19:14:11 I have one very similar to the one Will linked, FWIW. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Crazy Bill the Eel Killer on 02/22/24 at 11:53:45 If you want a high quality American made solution from the maker of Goertz audio cables https://www.bridgeportmagnetics.com/bmg-product/second-generation-balanced-power-system/ Good luck. Crazy Bill P.S. Check out my thread ZP3 A Humdinger ! Had huge hum problems with my new ZP3 that simply didn't exist with the phonostage it replaced, a Sonic Frontiers Phono 1 w/ SE+ upgrades. Put in the ZP3 with everything else exactly the same, and unlistenable hum. It was so bad I decided to investigate other RIAA preamps, so I ordered an iFi Audio RIAA2 unit with upgraded power supplies, and a plug in noise filter that also checked the status of the AC power. To make a long story short, checked the receptacle and it showed a bad ground. Mind you, using standard electrician's testers ( like the guy who came to your house ) showed everything was perfect. But the iFi tester showed bad ground. Had another outlet on the other side of the living room. On the same circuit as the bad one but it tested good. So I ran a 12/3 extension cord from the good outlet and powered up my system. Nirvana. Everything sounded great and was quiet. Again, good luck. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by thevinoman on 02/23/24 at 15:05:47 Update on what you might have found? |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 02/23/24 at 16:57:02 Sorry for the lack of response, been pulled into work! I'll be able to update tomorrow :) |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Bluemage on 02/29/24 at 02:05:50 Hey, man, just wondering if you’ve made any headway. I’m near the top for my 300b, which I’d planned to pair with AL5s! Rumor is that they’re getting some kind of update this year, and I’ve been holding out for that. I do appreciate your thorough analysis, and your document therof, here on the forum. I really hope you sorted your problems out, and enjoying your 300 to the absolute maximum! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by 4krow on 02/29/24 at 03:50:46 I have two units coming in for repair and each of them is a hum problem. Don't feel alone. One unit (Carver C-9) looks to have a jack that slanted on the rear panel, so I am betting that is a very possible issue in that case. The other is actually a preamp that I built! Maybe shipping problem? Dunno. It definitely seems to be more of a challenge. There are times that 'how' the components are connected to the AC power matters, i.e. a ground loop. One of the suggestions to even use a different outlet (on a different circuit of AC) will give you an idea. Unfortunately, it is true that many service people out there won't really investigate past what a meter tells them. Or worse yet, what a little plug identifier that is used to determine polarity, ground and earth would tell them. Glad that thought of tightening the contacts at the panel. A lot of grief can come from there. Same with every outlet in the house. That is one of the first things that I do if I move into a new place most AC outlets are crap and have been installed poorly in some cases. Each outlet in a string of outlets can cause a problem. As you go along make a check off list and order that things were done. It will help you in the end. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Bluemage on 02/29/24 at 20:37:02 I had my heart set on La Scalas with my Sarah, but now I’m rethinking in a big way. Perhaps, a compromise is in order: less efficiency to give up the horn-loaded bass. Maybe I’d be better off with the Cornwalls. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sam V on 03/01/24 at 03:40:43 I've had 120hz hum issues with my SE84UFO25 as well (see this thread: https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1621262294/50#58 ) and as far as I can tell, it's power supply ripple, an inherent byproduct of converting AC to DC. I've got another tube amp that also has some ripple but it's lessened by having a choke on the power supply to the point where it's not audible from my listening position (whereas the UFO, I can hear it). If it is ripple, all the power regenerators in the world won't do anything, because at the end of the day its the smoothing out of the AC waveform itself that's the issue... as long as you have AC going in (which, you do), you've got the potential for ripple. There are ways to mitigate it within the design of the amp (choke, capacitors), but those mitigations can't easily be changed/swapped (other parts of the amp rely on the specs of these things to operate correctly). It's definitely frustrating, I do wonder why some people seem to hear it and others report their amps being dead silent... My suspicion is the all hum, but if your room is big enough and you're far enough away, you won't hear it since it is fairly quiet. If some truly are dead silent, well, then, I'd love to know how to get mine to be that way too! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by MikeinMontana on 03/01/24 at 03:54:57 Sam. I hate hum and cannot tolerate any. Had to deal with a sub for several months before fixing it. Found out it was the plate amp that was slowly going out. caps etc. Replaced plate amp and perfection~ Our new Zen UFO is dead silent! Promise! [smiley=icqlite20.png] I may be falling apart at the seams, but by God, my hearing is golden! Doc even says so~ Made me feel good for once... ;D Take care ~ Mike |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sam V on 03/01/24 at 13:51:26 Mike - If you put your ear right next to the speaker, is it still dead silent? E.g. if i use my phone's decibel meter, I get about 55 dB right next to the driver (vs ~30 dB for just the room). Where I sit it's barely audible, but it is there. If it's legit silent at the driver (I have a solid state amp that is), then I'm flummoxed and would love to know why some are silent and others aren't. I've tried all manner of power filtering/cords/different circuits in entirely different houses/buildings, so I don't think it's power related, but who knows! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by HockessinKid on 03/01/24 at 15:00:31 I understand that if you drink enough Mad Dog 20-20 (Ripple) you will not hear any hum. You will of course wake up the next morning with a headache. It's all about trade offs😂. HK |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 03/01/24 at 15:43:50 Quote:
Yeah, I have also wondered about this because I've had both UFOs and UFO25s and they were/are silent. Heat death of the universe silent. Steve says the 120 Hz hum spec for a UFO25 is -58 dB, relative to some signal level, lets say 1 watt. So if you have 100 dB speaks that makes the hum 42 dB @ 1 meter. If your speakers are 90 dB that makes it 32. You don't say (or I missed) what kind of speakers you have. I also wonder if you have calibrated your iphone dB meter? My understanding is the meter is pretty good, but it needs to calibrated if you want to trust the actual numbers. I don't have any answers, esp. if you have thoroughly investigated your power. What about tubes, esp. the rectifier? They can matter too. It also may be some builds are just quieter than others, although I have no technical justification for that. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sam V on 03/01/24 at 15:56:48 My speakers are homemade using MarkAudio Alpair 10-P drivers, but I've also tested with Klipsch RP-600Ms too, exact same result. I've tried multiple different rectifiers, power, input, and voltage regulator tubes, nothing has had any effect on the hum. Like I said, it's barely noticeable at the listening position, but it is there in a quiet room. I feel like a plausible explanation here would be that filter capacitors in the power supply vary slightly even within spec, so the ones in my amp don't smooth out the ripple quite as well, but otherwise, I've got nothing. Believe me I've tried it all! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by JBzen on 03/01/24 at 16:16:15 It may be the power transform bell covers screws that pass through the laminations creating hum. It happened on my zkit Edcor output transformers. Had hum until the covers and screws are removed. Just saying. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 03/01/24 at 16:32:11 Quote:
Was it 120 Hz hum? |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by JBzen on 03/01/24 at 16:35:46 If memory serves correctly it was 60hz. My thought at the time was those screws passing through laminations created an dipole antenna of sorts. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sam V on 03/01/24 at 18:38:14 I did reduce some 60hz hum by sliding rubber washers underneath the transformer feet, which helped stop them transferring their vibrations to the chassis, that was a relatively simple upgrade/fix! But yeah the 120hz hum is most definitely electronic and not mechanical. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by MikeinMontana on 03/01/24 at 22:20:21 Hi Sam. I waited for Kathy to get back because I wanted her to listen for hum as well with me. Our two channel system consists of our new Zen ufo amp, hooked to Klipsch ChorusII speakers (101 db, 1 watt-1 meter). The only source is our Oppo bdp-103 player. We put an ear right next to (almost touching) all three drivers, ( tweet, mid and 15 inch woofer) and heard absolutely zero hum. This is the first time we listened for it that closely before. I am currently playing an ELO Flac file from a usb drive on the front slot of the oppo. No hum on cd's played either. I really hope that there is a way to mitigate any of that for you. I will check on another, different day too. We do not live in or around a city, I don't know if that makes any difference though with power lines.. We listened with the volume level on the amp up and down. Music was paused of course. I wish I had another idea other than the ones folks have already suggested. All the very best Sam ~Mike |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sam V on 03/01/24 at 22:26:33 Interesting, thanks for doing that! The plot thickens! I wonder what could be the issue/if there's hope. Like I said, maybe the filter caps on the power supply? Dunno if anyone has any other ideas... |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Tony on 03/01/24 at 22:52:03 Hi Mike, Thanks for thoroughly investigating your amplifier's hum, or, better said in your case, the absolute absence of the amplifier hum. Bringing in another pair of ears to listen added to the validity of your results for me. And congratulations on how hum-less your system performs. I thought that all tube amps probably hummed to some extent, but your results argue against that conclusion. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/02/24 at 02:29:42 Hi everyone! Sorry for the long delay in updating, I had a few days out camping/hiking that was bookended on either side by intense work situations that I needed to put all of my attention into. So, since I last posted, I regrettably haven't made much progress in resolving things. When my landlord heard that I'd had an electrician over, he insisted on bringing his own electrician over just to double check everything for me. Everything checks out, the wiring is actually much more modern than the rest of the house, and the ground is definitely good. I feel pretty satisfied that if there is a problem with something, it is not the wiring in my home. I had a back and forth with Rex, the audiophile oriented electrician someone linked earlier in the thread, and that seemed to be his conclusion as well. I also got my own outlet tester, and no problems detected anywhere. I did try lifting the ground with a 3->2 prong adapter, it made absolutely no change. I also tried shorting the two input RCA jacks (something that Rex and people in the Klipsch thread suggested is important to accurately characterize the hum), it made absolutely no change. Steve asked me to send him a video recording of a decibel meter recording the room with the amp off then on. I obliged, and he replied that he really thinks that there's nothing wrong with the amp, and that this is just the unfortunate consequence of the super high efficiency of my speakers. He also suggested that speaker placement and room acoustics could be contributing to the problem -- but fwiw, the hum is bad anywhere in the room, and not any worse at my listening position. Room is 400 sq ft. I've gotten confirmation from someone over at the Klipsch forums that they had the SEWE300B and tried pairing it with ~100 dB speakers. He troubleshooted the situation with Steve and it seemed like they came to the same conclusion, and he ended up selling the 300B. Quote:
When I hear something like this, it gives me pause/hope. The hum I get from my pair of UFO25s, although ~3dB less than what I get from the 300B is definitely still unbearable (mid-50 dBs at listening position). But then, James, your speakers are ~94.5 dB, and that is a huge difference. Even so, though, I wouldn't expect "heat death of the universe" silent even at 94.5 dB efficiency, given what I'm experiencing at 105. Indeed my 95 dB Zu DW6s have faint hum at listening position when hooked up to the 300B. But I actually haven't ever tried the DW6s with the UFO25s. I'll try that when I get home on Monday! Again I really appreciate everyone's suggestions and investment in helping me troubleshoot and understand what's going on. At this point it seems like we're trending towards certain Decware amps (300B, UFO25) not being a correct match for anything around 105 dB efficiency (and anecdotally maybe the 300B isn't a good pairing for even 100 dB?). If we do determine that this is true, this is really good information to be out there for anyone on the waiting list who has been planning on pairing the 300B with La Scalas and Klipschorns (I've spoken to a couple already), and it gives them an opportunity to re-think their plans! I feel like I've tried all of the troubleshooting suggestions people have put forth so far except for balanced isolation transformer. But I'm still open to trying things and if anyone has any other suggestions I'm happy to hear them :) (also, again, for anyone that's still suggesting ground loops, I think I have pretty conclusively ruled that out: the hum is exactly the same even if there is no input to the amp, and the amp is the only thing plugged in to power -- feel free to let me know if this doesn't rule it out!) |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Karl on 03/05/24 at 18:53:25 Sorry to hear about this frustrating problem! I think it would be interesting to see what happens when you use your Sarah300b in a different system. Bring it to a Klipsch dealer or a friends house. At least then you can answer the question if there is something intrinsic to the amplifiers causing the problem. Tubes, transformers etc. My bet is that there isn't something inherent in Decware designs compared to other tube amps. At the very least, if you decide to sell the Decware's you can say they are totally silent in other peoples setup. -Karl |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/05/24 at 19:17:44 Yes, I do still want to take it somewhere that has La Scalas or KHorns set up to try it out and get peace of mind, but that's easier said than done. Unfortunately, I don't have any friends with passive speakers (young people...) and dealers don't usually have LS or KH set up to demo, and would only want to do so if they think they might make a sale. Quote:
My understanding of what Steve has told me is that there is absolutely inherent hum in his amps that is designed to be quiet with less efficient speakers. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by MikeinMontana on 03/05/24 at 19:32:12 Thought about that too Karl. Folks in large cities..or near one, would sure be worth a try. If he lived near, I'd ask him to bring the amp over as our setup has absolutely zero hum. and that's with a sub hooked up too. ChorusII's at 101db I'd think would work. But....we are in the sticks people... [smiley=icqlite20.png] Like you said, maybe a Klipsch dealer, or friends home. We had a sub that really screwed with us for quite some time several years ago. Hummed like a sob. It all started after a thunderstorm one night. Lightning all over. I changed out a long sub cable (35 footer for a blue jeans cable one) a huge difference. But still some hum left. Replaced the plate amp and poof. Almost completely silent now. Have to put my stupid head into the driver to hear much at all...I hope mk gets this going as it should sound nuts (good!). I would have loved a set of LaSacalla's at one time..but were always just a bit too big to fit our front wall area. That strike shook me up that night..wasn't ready for it that close. :D |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by MikeinMontana on 03/05/24 at 20:24:50 Sorry about that mk. It takes a while for me to complete a paragraph, and you had a reply all set. :D . |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Carl on 03/11/24 at 14:57:40 MK, I may have missed it. Where are you located? |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/11/24 at 18:15:46 I'm in Los Angeles! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Carl on 03/11/24 at 20:04:09 Too bad. I have a couple pair of speakers you could have tried. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/11/24 at 20:18:22 Thanks! I'll actually probably have a chance to try the amp on a set of Klipschorn AK6 (exact same drivers and efficiency as my La Scala AL5) next week in another location. Assuming the hum is the same there, I'll feel pretty confident with the conclusion that what I'm experiencing is just the inherent hum of the amp, meaning it's just not a great match for super high efficiency. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Bluemage on 03/11/24 at 22:03:04 I can’t wait to hear your results of this test! Please, keep us posted! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sam V on 03/13/24 at 19:18:55 I'm still curious if there is anything that can be done (filter cap swaps, etc), since it seems like some amps are dead quiet with high efficiency speakers ... Like, one of 2 things must be true: 1) All the Zen Amps hum but for some reason some people don't hear it, or 2) Some of the Zen Amps hum, and there must be some reason as to why. If it's #2, I'd love to know what the reason is! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sam V on 03/13/24 at 19:27:06 On that note, if there's anyone in the Boston area with an SE84UFO25 that's dead silent, I'd love to meet up and compare amps, see if it's dead silent in my setup and/or mine hums in yours! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/13/24 at 19:51:07 Sam, so I think that everything that I've found so far is mostly number 1, but with a little bit of number 2! My understanding comes from my discussions with Steve, my own experiences with several different Zen amps, and discussing with others who have had experiences pairing Zen amps with extremely efficient speakers. But I don't claim to know for sure that everything I'm saying here is true. I make these statements assuming that there are no power issues or ground loop issues which will also independently cause hum problems 1) All Zen amps do hum, to a certain extent. Different models hum have different levels of hum which are inherent to the design of a Zen amp, and is tuned differently for different models/designs (e.g. in my testing and confirming in discussion with Steve, SEWE300B > SE84UFO25 > SE34I.5), and this hum can not be eliminated. Based on reports/reviews I've heard from a couple of other people, I suspect, but have not confirmed, that the inherent hum level of the SE84UFO2.1 is less than the SE84UFO25. 2) The extent to which you will hear this inherent hum depends entirely on the efficiency of your speakers and how far you're sitting from them. I think that the reason that some people say that they don't get any hum from their Zen amp is that the level of inherent hum of the model that they have, combined with their speaker's efficiency rating (usually mid to high 90s), leads to a hum that isn't loud enough to hear at normal listening position, and can probably only be heard by listening right next to the driver. Or, often in the worst case, a low level of hum is audible at listening position, but not enough to be a problem. 3) My case is the worst possible scenario because of the 105 dB efficiency of my speakers, and it makes the SEWE300B and SE84UFO25 (unless in differential balanced mono) unusable. I will say, though, that the amount of hum that I'm getting through my 95 dB efficient Zu DW6 paired with the SEWE300B is definitely noticeable at listening position, although not nearly as bad as through my La Scalas. Still a surprising amount, though. If Steve's spec is that on a 95 dB speaker I shouldn't be hearing hum at my listening position, then it really does seem like something is wrong here. He doesn't seem to think so, though. Anyway, Sam, do you think there's info/evidence that contradicts the understanding that I've come up with? I would also really like to understand what's happening :) |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/13/24 at 19:55:45 Also, add in with the above that everyone hears a little differently and tends to be inexact with language in different ways, and I'd expect that to account for small discrepancies in experiences. Same thing Sam said goes for me in socal: if anyone has a UFO25 that they believe is truly dead silent (which by what I've suggested above wouldn't be possible), would love to compare with my two UFO25 amps! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Sam V on 03/13/24 at 20:03:33 Yeah, I tend to agree with your assessment, I've got the UFO25 in a small room with relatively sensitive speakers (not 105dB, probably low 90's, so I'd imagine with 105dB ones it would be not great)... the only reason I'm not 100% sure is because we've got eyewitness testimony to them being "heat death of the universe" silent, and they're low wattage amps so I'd assume most people aren't using sensitive speakers, not like, 85dB. Hopefully we'll find out! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/13/24 at 20:10:45 Agreed! If there really is variation to the degree that you're hearing hum on low 90s efficiency but CAJames is really getting silence, and it's a difference in the amps themselves, then this does need Steve's attention. Having an amp like CAJames' could mean the difference between being able to comfortably use a single UFO25 on my La Scalas vs needing having to have a pair in balanced mono for it to be useable. But based on my interactions with Steve, I would be surprised if he agreed that any UFO25 could be "heat death of the universe" silent with an ear to the driver. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 03/13/24 at 21:25:54 Quote:
I will say this, if it is 120 Hz ripple from the power supply, I think that would be more or less the same in both channels, so it would cancel out if you were doing balanced differential. I was one of those who claimed that my UFO25s were silent with my 95ish dB speakers. And I believe they were when I first got them, but I stuck my ear against the speaker cone the other day and there was barely audible “noise.” Some of it is tube noise, but there was a little bit of hum as well. It isn’t audible 6 inches from the driver, but it is there. Perhaps it is a function of many more hours on the amp, and/or my current tube set. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by cmdc on 03/13/24 at 23:09:57 I’ve been following this thread for a while now, so I’ve had the chance to do several tests using my UFO25 and Zu Druid Mk V speakers, which have sensitivity of 101 dB. I’ve used two different sound meters, and three different speaker cable combinations. I did 3 new tests on each channel today. With the amp and speakers connected by Decware’s ZFocus cable, I averaged 34 dB (range 32-36 dB) at 1 meter from the speaker driver. This is just above the background level of my room (32-33 dB), which is all the meters registered when I moved back to 6 feet from the driver. This was with the amp gain set to a level that delivers a baseline 82 dB at my listening position 10 feet away. That 82 dB baseline is actually slightly above my typical comfortable listening level, so if anything the 34 dB hum at 1 meter is slightly louder than I would typically experience. When I had the UFO25 and speakers wired with the M22759 wire that is the basis for the ZStyx cable, the hum at 1 meter measured just slightly higher at 36 dB, again, just 3 dB above the background noise level in my room. And again, basically inaudible at any distance greater than 6 feet. Out of curiosity, I did the same test with my 40 wpc ZMA and got 34 dB at 1 meter. 101 dB speakers are, obviously, 4 dB less sensitive than 105 dB speakers, but they would generally be considered pretty sensitive speakers. I have run the Caintuck Lii 15 OBs (97 dB) with the ZMA, the UFO25, and currently the standard SE84UFO, and never noticed any audible hum at any distance. Indeed, the latter is currently running in our family room and is so dead quiet that I sometimes forget that it’s on for hours or days at a time. The default gain on this amp is set a good bit higher than in my listening room, because the family room is a much larger space and I generally fill it with much louder music. Take from this what you will, but my own experience doesn’t suggest that there’s an omnipresent hum under normal operating conditions that other Decware listeners just aren’t hearing, even with relatively sensitive speakers. One final addendum on this: I use my Decware amps with a ZRock2, but without another preamp. As a result, I rarely set the gain on my amps above the 10 o’clock position. As a further experiment, I moved the amp gain to the 3 o’clock position, which someone might use if they were running the amp wide open and using a pre-amp to control the volume. This delivered 39-40 dB of hum at 1 meter, dropping to a still modestly audible 36 dB at 2 meters, and still becoming inaudible at my listening position. This suggests that if you’re running an amp and pre-amp together and encountering a hum at your listening position, modestly lowering the gain on the amp and adding offsetting gain on the preamp might help. That said, given that mk60 experienced hum from his Sarah without a preamp, and with amp set at zero gain, it seems unlikely to help in his situation. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by MikeinMontana on 03/14/24 at 19:16:19 Excellent post cmdc. Really has me thinking....which is what caused all of my problems in the first place.. ::) This thread has had me checking for hum many times now on our own setup. We both hear none through the speakers (101db as well). The sub when it is on puts out a very faint hum when your head is right next to the driver. 3 feet away though..quiet. Our son purchased Forte4's a couple years ago. 99 db, no hum either. We both now own recent Zen UFO amps. This is an interesting topic. I cannot stand hearing hum at my listening positions at all~ I have an older analog radio shack db meter and out of curiosity am going to compare the hum from the sub and any from the speakers. Second guessing I guess.. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by 4krow on 03/14/24 at 23:13:48 I just sold a very nice preamp that I made to someone who owns Khorns. Here we go again. In my system little to no hum. In his, hum is there but only when the level is turned up louder than at a normal listening level. He sent the pre back to me and I did a star grounding which helped his hum problem, but was still there. In the end he decided to keep the preamp based on the musicality that it had over some of the other preamps that he owns. Synergy is not easy to get in every system, and as much as I like some of the speakers out there, I see no reason to get above 95dB for sensitivity. you are likely headed for any issue large or small to be noticed above the goal of recreating just music. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/17/24 at 06:11:51 Thanks, cmdc, for taking the time to do that, this seems like an important data point for this conversation! That you're getting basically no hum from 101 dB speakers on your UFO25 is definitely interesting (and encouraging) to me. Both of my UFO25s hum the same, and loudly, on my 105 dBs, and you can hear that hum anywhere in the room (12x30). But your report is consistent with, for example, Steve Guttenberg really enjoying the UFO25 on his Cornwall IVs (also 101 dB). Does anyone know the math on SPL as a function of distance and efficiency off the top of their head? For example, I've got my pair of 105 dB speakers set up ~10 feet from my listening position, and I measure, say, a 55 dB hum at listening position (that's about what I get from each of my UFO25s). Leave all of the geometry the same, and replace the 105 speakers with 101 dB speakers -- if everything else is the same, how loud would one expect the hum to be at listening position? I'm too tired to think about it right now, but may figure it out tomorrow. I actually don't think I've ever hooked either of my UFO25s up to my 95 dB DW6s -- I'll do that when I'm back at home next week. I expect no hum at listening position. Otherwise, it really seems like something is up. Also, I'll emphasize again that unlike the hum that cmdc seems to be describing (seemingly changes with cables, pre-amp, and volume?), mine is dead constant when you switch out cables connect or disconnect a pre-amp, turn gain up/down. Ground lifted or normal. Doesn't matter, hum's the same (only changes with amp, UFO25 vs SEWE300B). One thing that really has me scratching my head here about the 300B amp is that Steve seems to have confirmed that it's an absolutely wonderful match for his 103 dB headwreckers. With how loud the hum I'm getting on my La Scalas is, I would imagine it would have to be pretty similar to what you would hear out of the headwreckers, and yet that seems not to be the case? This points me back to there being an issue elsewhere external to my amp. But then Steve has told me explicitly that the hum I'm hearing is purely a result of my speaker efficiency (and possibly speaker placement and room). So at this point, I really have no idea. But I continue to endeavor to figure it out by getting more data! |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by CAJames on 03/17/24 at 14:57:06 Here is a calculator for SPL vs distance. It will overestimate the attentuation (underestimate the SPL at distance) because a real speaker is bigger than a point source, but it should get you in the ballpark. https://www.wkcgroup.com/tools-room/inverse-square-law-sound-calculator/ |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Tony on 03/17/24 at 15:48:08 What, wait....the "Sound Inverse Square Law?" This explanation may be precisely what MK60 needs, but I'm going to need another cup of coffee this early Sunday AM before going any further with this one :) Good luck pursuing an answer, MK60. Your patience and ability to stay focused and optimistic are admirable and instructive. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by mk60 on 03/18/24 at 03:52:45 Yeah, right, inverse square makes sense. Anyway, the answer to my intended question was obvious my brain was toast last night -- whatever SPL I have at listening position on a 105 dB speaker will simply be 4 db lower if it were coming from a 101 dB speaker. So, assume the "intrinsic hum" to be a constant level signal coming out of the amp output and into the speaker. Then: 1. If I took one of my UFO25s that hums out of my La Scalas at ~55 dB, and dropped in Cornwalls or Zu Druid Mk 5s instead of the La Scalas, I'd expect ~51 dB. I think that's still a reasonably noticeable hum? 2. If I take my SEWE300B which is generating ~58 dB of hum out of my La Scalas, and I replace the La Scalas with Steve's 103 dB headwreckers, I'm still at 56 dB of hum, which is not good. It really seems like what I'm experiencing with my UFO25s is out of line with what others have experienced with their UFO25s, and what I'm experiencing with my SEWE300B is out of line with what Steve is reporting about his experience with his headwreckers. But in my last conversation with Steve about this, he really seemed totally sure that what I'm experiencing is expected. Maybe it's time to bother him again? Although I hate to. Testing my 300B on the pair of Klipschorns I'm auditioning in another location has been pushed back a week. |
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Title: Re: Inherent Hum of Zen Amps + 105 dB Efficiency Post by Samuel Bayles on 04/10/24 at 01:20:07 new to this forum and thread. hum is super frustrating, i feel your pain. i didnt see that you ever tried an isolation step down transformer. get a 1000w 120-120 isolation step down transformer. if the hum is coming from house/wiring it will fix it. ive battled a couple of recalcitrant hums over the years and this fixed them. |
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