Forums https://www.decware.com/cgi-bin/yabb22/YaBB.pl AUDIO FORUMS >> General Discussion and Support >> Hum questions https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1615046257 Message started by Eldergod on 03/06/21 at 15:57:37

Title: Hum questions Post by Eldergod on 03/06/21 at 15:57:37 Morning everyone! Received my SE84UFO2 yesterday and was super excited to start listening. However, very quickly I realized I had a bit of audible hum emanating from my speakers. The left seems to be a higher frequency than the right, but they are both exhibiting an audible hum. I thought maybe I had too many things plugged in so I moved the amp and speakers out of my room into a separate space. No change. I swapped the two output tubes thinking one might be a bit different from the other, but again no change. I can hear the hum in the transformer if I put my ear up to it, although at an obviously lower volume vs the speakers. Not sure what that indicates. Issue with the hardware? Dirty power in the house? Thoughts? I guess I can place a call to Steve Monday. Not sure if I can post a video, but will work on it today. Any help/thoughts/suggestions welcome, and thanks.

Title: Re: Hum questions Post by Eldergod on 03/06/21 at 16:16:23 Some other random thoughts and observations: is this something that settles/goes away with burn in? Is this just the nature of tubes? I also noticed the transformer gives off a slight vibration that seems to coincide with the hum. Normal...?

Title: Re: Hum questions Post by Eldergod on 03/06/21 at 16:25:25 Sorry for spamming my own post. Also wanted to convey the hum is not affected by volume.

Title: Re: Hum questions Post by Archie on 03/06/21 at 17:18:51 If it's not being amplified (gets louder with more volume on the pot) then I'm not really sure.  In the past I've had luck moving my ICs away from any electrical outlets.  Proximity to power cords didn't seem to matter, just the wall outlets.

Title: Re: Hum questions Post by GroovySauce on 03/06/21 at 17:28:36 A slight transformer hum seems typical. On the ZMA I can always hear a very soft hum from the trans. With the volume pot turned up all the way and I can hear a faint hum from the speakers when my ear is near. F15's W15's. All good with spamming your own tread. I know how it feels to want to listen to music and something isn't right. Do you have anything that blocks DC offset? this is a common hum problem. If you hold the trans tightly does the hum get lower? Have you tried a different input tube? Every tube based stereo I've ever been around has a tiny amount of hum. At the listening position it shouldn't be  drawing attention to itself. I notice hum in recordings not my system.

Title: Re: Hum questions Post by CAJames on 03/06/21 at 17:29:55 In my experience a lot of times transformer hum is power related. But for sure I'd let the amps burn in for 20+ hours and re-evaluate.

Title: Re: Hum questions Post by piezoman on 03/06/21 at 18:11:39 FWIW, I literally have zero hum in my current system. However, the system I had prior which was powered by a Rogue Chronus Magnum tube integrated amp had a noticeable hum at the speakers, which could be picked up 8 feet away.

Title: Re: Hum questions Post by Eldergod on 03/06/21 at 19:45:27 Thanks all for the feedback so far. Letting it burn in seems like the next best thing at this point. I have tried multiple spots/receptacles now with no change. Definitely mostly a left channel thing. It’s there and very low hz in the right, but not nearly as prevalent. Definitely related to the trans. It has picked up slightly in vibration and volume from that point now. Really strange. Letting it stay on for some extended time, with the occasional cool down to cycle between now and Monday. We’ll see. Definitely frustrating. I can tell the sound is out of this world, but the low fly buzz/drone is not acceptable as is. FWIW, listening on Caintuck Betsy diy clones. Source, no source, speaker wires have no effect.

Title: Re: Hum questions Post by Geno on 03/06/21 at 19:54:24 Elder, So exactly how are you set up? What is your source?

Title: Re: Hum questions Post by piezoman on 03/06/21 at 20:00:45 Eldergod, Pergaps some more burn in will maje a difference, maybe not. Input tube is from Steve? Have you tried another one? You might want to talk to Steve on Monday if possible.

Title: Re: Hum questions Post by Eldergod on 03/06/21 at 20:09:59 Geno, phono, cd, and iPad sources. Changed them all in/around. Doesn’t seem to affect it at all. Piezoman, yes all tubes from Steve. I haven’t purchased any others yet to roll. I may look getting another input tube to try since I switched the outputs already to see if it changed anything L to R (it didn’t).

Title: Re: Hum questions Post by Eldergod on 03/06/21 at 20:31:51 https://youtu.be/hL8vSHAo0Wk https://youtu.be/R1TFv50zIYQ See if these links work. Uploaded a few secs of the trans and speaker to YouTube.

Title: Re: Hum questions Post by Geno on 03/06/21 at 21:01:54 Have you tried disconnecting all sources so that all you have are speaker wire and speakers connected to the amp?

Title: Re: Hum questions Post by MrDerrick on 03/06/21 at 21:49:03 Eldergod, Steve has a very good article on troubleshooting hum problems posted in the Articles Section. Your owners manual also has a hum troubleshooting chart. Is it possible that you have the gain setting set too high somewhere in the signal chain? Or that the input tube bias is not set properly for your gain setting? I can make my SE84UFO25 hum through my horns with certain combinations of input tube, bias and gain.

Title: Re: Hum questions Post by Eldergod on 03/06/21 at 22:35:16 Geno, yup. That’s where I am currently. MrDerrick, yup, read through all that. No extra gain between sources, and input tube bias set to low position. However, this doesn’t make any difference in hum, but I can definitely tell which way is low and high listening to music.

Title: Re: Hum questions Post by Geno on 03/06/21 at 22:51:59 If you have a music store close by that sells guitars, etc. you could get an input tube there. Update: I’m sorry but I’m getting my tubes mixed up. It is primarily the 12ax7 that guitar amps use.

Title: Re: Hum questions Post by Geno on 03/06/21 at 23:14:17 Just to rule it out too, do you have another power cord you can try?

Title: Re: Hum questions Post by MrDerrick on 03/06/21 at 23:49:02 Eldergod, If you are comfortable with trying some AC power related testing; Turn off all of the branch circuit breakers in your AC panel except the branch circuit feeding your audio system. If the hum disappears, then there may be a problem with one of your other branch circuits or a load connected to them. Turn the branch circuits back on one at a time until the hum reappears, that will be the branch circuit that has a problem or a load with a problem connected to it. You mentioned trying a different space ( branch circuit ? ) but if there is a problem somewhere in your other branch circuit wiring or with another connected load, the problem would not be isolated / eliminated. I do not feel comfortable suggesting any other tests AC power related unless you have extensive experience. I have 40 plus years in AC power, grounding and bonding in the telco industry. Maybe your previous amp was more forgiving of an issue that you did not know you had?

Title: Re: Hum questions Post by Eldergod on 03/06/21 at 23:57:07 Geno, that’s a great idea. Had not thought of that yet. Lemme go rummage around... I may have one. MrDerrick, I hadn’t thought of that either. I’m knowledgeable enough to do that tomorrow to troubleshoot.

Title: Re: Hum questions Post by Eldergod on 03/08/21 at 14:43:20 Okay, follow up from the weekend.  Tried another powercord, but no difference.  Also tried playing with the electrical branches, but nothing really changed either.  Took the amp, speakers, and my iPad next door to a neighbor's house to try it with no change.   That all being said, and in the meantime, I was running the unit and burning it in via heat cycling.  While on, I was using it to play quietly as well.  The issue has definitely subsided since Fri night/Saturday.  Probably lessened by approx. 60-70%ish which is good.  I'm able to start enjoying the amp/music now, and feeling less anxious about the issue.  Definitely seems to be transformer related hum/buzz/vibration.  And interestingly enough mainly in the L channel now.  The R is still there but a much lower Hz and barely audible unless I put my ear to that particular side speaker.  I'm curious if anyone else's unit transformer has a slight vibration you can feel if you cup the trans in your hands lightly while turned on?  Also, both speakers (but particularly the L) if I touch the cone while the amp is on (regardless of whether an source is connected or volume level) creates vibrational movement/oscillation which of course is what is producing the audible sound.  I guess I'm asking if your amps do the same where you can feel any energy moving the cone with the amp simply turned on? Regardless, back to the music for a minute now that I had some time yesterday evening to really dig into it since things are settling down.  I've never really experienced great synergy between and amp and speakers until now.  Listening to tracks of music through this amp and speakers is so different than anything I've encountered.  I can't really even explain it.  Even the lower extension on the Betsy's has so much more presence.  I played Sting's Desert Rose on a whim and was struck by the weight of the bottom end from a full range driver that shouldn't really demonstrate much below 80-100hz.  Not that there was slam there, but I had to check to make sure no sub was connected. The clarity was incredible on my 'test' tracks.  It was like tuning in the radio (showing my age) and hitting that perfect spot where all of a sudden the noise and interference I have been accustom to and normalized was suddenly gone.  Or washing your car in early spring, deciding to also clean the inside of your windshield on a whim, and then driving down the road thinking "Woooowwww..... this is SO much better.  Why have I not done this before?" Looking forward to more listening this week and next weekend to get more time behind the wheel.

Title: Re: Hum questions Post by piezoman on 03/08/21 at 15:02:06 Eldergod, That's really great news so far! I'm glad the situation has turned the corner like that. You have a wonderful system. Brad

Title: Re: Hum questions Post by Eldergod on 03/24/21 at 13:57:26 Closing the loop on this in case anyone else has an issue and does a search for something similar.  It's been a few weeks now, and the perceived issue has resolved completely.  I am certain it had to do with the transformer needing time to heat cycle and/or burn-in/season.  There is no audible hum now, and I am able to just sit back and enjoy the music!

Title: Re: Hum questions Post by Steve Deckert on 03/24/21 at 19:37:08 That's great news!  My money says it was the input tube. Steve

Title: Re: Hum questions Post by canonken on 05/20/21 at 02:28:20 Wanted to ask here. Have 100-200ish hours and a few dozen heat cycles on the amp.  Still hearing hum (through the speakers, 10-20 feet away - quiet, but it is there when no audio is playing). I have tried a few different tubes (thought not exhaustively), unplugged interconnects, etc. and there is nothing I can do to raise, lower, or change it.  I do hear a hum from the transformer when I put my ear close to it (that hum is NOT distracting and I don't care...unless it is a signal there is an issue there). I am using these speakers: https://www.madisoundspeakerstore.com/full-range-speaker-kits/fostex-bk-12m-folded-horn-kit-pair/ Almost all of what I am hearing is mid-bass hum from the horn (vs. driver itself, though I can feel the hum if I put my finger on the driver). I measure 0.01 volts on the speaker posts with no signal vs. <0.001 on other amps...if that means anything.

Title: Re: Hum questions Post by Archie on 05/20/21 at 06:03:54 canonken, I don't see where you posted about this before.  Is the hum there when your source isn't connected?  Without my source I have to turn my volume way up to hear appreciable hum with my ZMA.  As I posted near the top of this thread, I got rid of a persistent hum by moving my ICs away form any electrical outlets.  I too get a quiet mechanical hum from some of my transformers -- but not all of them.

Title: Re: Hum questions Post by canonken on 05/21/21 at 00:15:31 Archie, here is the thread: https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1621262294 No change to the hum when I unplug the RCA cables.  It seems very 'stable' meaning things like moving cords, moving the amp doesn't make it better or worse. Thanks, Ken

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