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https://www.decware.com/cgi-bin/yabb22/YaBB.pl AUDIO FORUMS >> General Discussion and Support >> Low speaker hum/buz even when amp isnt plugged in. https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1656287548 Message started by Kedros on 06/27/22 at 00:52:28 |
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Title: Low speaker hum/buz even when amp isnt plugged in. Post by Kedros on 06/27/22 at 00:52:28 So I sat down the other day in front of my speakers and noticed that it was emitting noise. A low level buzz/hum and I thought this very strange as my amp wasn't turned on. so I walked over and proceeded to unplug my amp from the wall and the sound was still thar. It only went away after unplugging one of the speaker wire from the unplugged amp itself! So my question is, does anyone know what would be causing this? I have used multiple cables and speakers with the same result. Even after the amp is unplugged for many, many hours its still going. The amp in question is the SE34-I. This is not potentially causing damage to anything is it? I have been keeping the speaker wire unplugged until I go to use it, but I have still been using it.. Thanks Dylan |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by CAJames on 06/27/22 at 01:21:19 That is pretty weird. It is always a good idea IMO to swap out the tubes if you haven’t already done so. Also there are internal fuses that might blow although it isn’t clear how that would cause your problem. When you say the amp has been unplugged for many many hours do you mean a week or more? Pretty much the only thing I can think of (besides the tubes and fuses) is there is something wrong with a power supply capacitor and it isn’t discharging correctly. If it were me and new tubes and/or fuses didn’t fix the problem I’d contact Steve. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by will on 06/27/22 at 04:10:47 Weird indeed! And out of my range of experience, but I will offer some brainstorm thoughts, and hopefully if I am off, someone who knows will correct. If there is no power to the amp, even with the power cord hooked up, I can't quite feature it being something in the power path of the amp... like internal fuse connections or tubes... but not for sure. I am ignorant about the internal fuses as my amps don't have them. But looking at pics, it seems they are on the rectifier circuit. So if a fuse was bad, wouldn't the rectifier not light up? Is it possible that it is a strong magnetic field that your amp and/or cables are acting as an antenna to pick up. But to make the sound at the speakers for extended periods without the amp powered up, wouldn't there need to be some power to make noise from the speaker drivers??? Could a strong interference field be enough to activate the drivers??? If you have it happening after many, many hours of being turned off, even if caps were still holding charge, wouldn't the noise at the drivers be draining that power off and eventually be quiet? But also, normally, I have some light hum here, and as soon as I turn off my amps, there is no noise. And doing modifications, I know some caps can stay charged a while without directly discharging them by playing the amp out without power... ie music playing, and power off the amp as a means to drain caps, and by double checking with resistors to ground internally... Anyway, my noise goes away as soon as power is cut, but some caps still have some charge. Also, seems interesting that it goes away removing the one speaker cable. Does it go away if you unplug the other speaker cable and leave the one you pulled hooked up? Could it be some proximity thing that the one cable is closer to a EMF or RFI noise source? Is this something new? Just recently noticing it, is it pretty quiet ... like something that you have to have your ear near the speaker to hear? Did you have anything plugged into the amp after pulling the power cord... Could noise be coming over from your pre or source or source cables? Have you added some networking or wifi to your setup that might contribute? Has your power changed in some way? I have never experienced this, but maybe more trouble shooting thoughts for a talk with Steve if needed. I would not hesitate to call Steve. Will |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Same Old DD on 06/27/22 at 04:54:24 There has to be something going on inside the amp that is not quite right. Hard to imagine an EMI or RFI source powerful enough to affect a speaker without it affecting everything else in proximity. It can't be external. It has to be the amp. Already mentioned, but contact Steve. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Yakatak on 06/27/22 at 05:55:22 Have you disconnected components upstream of the amp? Noise may be passing through from a CD player or preamp? |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Crazy Bill the Eel Killer on 06/27/22 at 14:50:55 Been there, done that. Don't have time now to go into details, but I had the same issue with noise in my headphones w/ nothing powered up. Eventually figured out that the ground on the plug was defective. My electrician tester didn't show a problem, but a tester that I got from iFi audio back in the day did. Plugged the whole system into another outlet that tested good, and the noise ( hum and buzz ) disappeared. I'd bet you have a ground problem. Pull all interconnects out of the amp. Leave the speakers hooked up, power it up and let us know what happens. Good luck. Cheers, Crazy Bill |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Same Old DD on 06/27/22 at 15:04:08 Thanks, Crazy, I would enjoy your dissertation expounded upon. Wrapping my mind around ways that might be cause. When you have time. Thank you |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by RJR on 06/27/22 at 15:05:05 FYI I have a wifi extender near my speakers which needed to be moved because it was causing noise through my speakers when everything was turned off. I had issues with my router when my system was set up in another room near the router. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by EdwardT on 06/27/22 at 16:21:05 Amp off and the speakers hum sounds like a power supply cap discharging but it would stop after a bit. I suppose a weird synergy between the cables and an external electromagnetic field can't be ruled out but I’ve not encountered anything like that and I’ve exposed electronics to external forces all over the continent. You've eliminated the speaker by unplugging it. Now attach the cables to the speakers unplugged from the amp and eliminate them as antennae. This sort of vexing problem can only be solved by methodically changing one element at a time until you discover the culprit. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Kedros on 06/28/22 at 01:06:34 Thank you all so much for the advice and input I really appreciate it. Okay I did some more troubleshooting based on everyone's advice.. I took all of the tubes (speakers made some weird noises while I took out the el34's), RCA connects, and the power cord out of the amp so that all that was connected was just the speakers plugged in. Now I was sitting on the ground with my ear to the speaker at this point reaching up to unplug the cables from the back of the amp. I could swear I hear something but its so low that I am probably imagining things. However NOW if I plug the power cord in the sound comes back. unplugging it makes it so low I think its gone. plugging an RCA cable in will get the same results as plugging the power cable in the noise comes back. But the best thing of all is even with just the speaker cables and no other sources. touching the speaker cables to pull them out with just my fingers brings the sound back just not as strong. It's gotta be a ground issue, right? So I took the amp down to my workbench and took the bottom off to take a look inside (its an impressive thing to see really, just wow). I couldn't see anything that was not connected but noticed something residue wise on a spot and when I put my finger inside I must have connected something because I got a pretty good shock from it. freaked me out a bit as i was not expecting that in any way lol. That's pretty much the extent of it so far I kinda stopped at that point and don't want to use it anymore, which really sucks for obvious reasons and my ufo25 wont be showing up anytime soon. Does anyone think if I still use it, I will be doing harm to anything? Other than the noise? It definitely seems like I have to send it back for repair as that's miles above my skill level. Has anyone had any experience with that, EI. sending something back for repair? I got it second hand so its not under warranty and with the wait list as long as it is I don't see this getting repaired anytime soon. I should just email Steve lol Thanks Dylan |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Geno on 06/28/22 at 02:10:35 Dylan, I would call Steve and talk about what’s going on. He can guide you. If he decides that you need to send it in, you would not be on the new component wait list. Repairs and mods are done separate from those. You should get it back in under a month. Good luck! Geno |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by CAJames on 06/28/22 at 03:03:04 Yeah, if you got shocked with the amp unplugged there is 100% a problem. Call Steve. Full Stop. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by will on 06/28/22 at 03:30:36 First I would ask, when you say you plug the power cable or ICs back in... Are they connected to other things, or just plugged into the amp? If on their own in the amp, perhaps antennas, if in the wall of other gear, perhaps ground. Did you have the amp off when you swapped the EL34s and got a weird sound... I always change tubes with the amp off. And if it gets noisy when attached to the wall power or ICs connected to other gear, it does sound like it could be ground issues... I have had this happen where my touching a connector, presumably me being another ground connection, makes the ground hum worse. I am not altogether convinced this needs repair based on your research pointing to ground noise. The shock thing could be what I was talking about before... Unless fully drained, the power caps can hold charge, and if you go inside and connect ground to the hot side with your finger or whatever, you will get a nasty wakeup zap. Judging from all this, you may even have a semi-"normal" hum, especially if you are using really efficient speakers. In my rooms, until I started modifying things, I alway had some hum from my Decware, though not a lot. And now, almost none with some internal work... but sometimes a small amount. If this is a hum you have to put your ear to the speaker to hear, I guess I might just proceed to enjoy while trying to set up cables to where they are distanced, and cross each other rather than being parallel and close, and if you can, plug all your stuff into the same receptacle (or strip/conditioner...) These might fix it for the most part. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by will on 06/28/22 at 03:41:37 Also, if you feel like you need to return it for work or a checkup, talk with Sarah or Steve, but I am thinking you could work it out with the normal repair rate, or you could somehow integrate the warranty checkup and change to your name... a full checkup that requires new tubes last I checked.... that is if you want the warranty. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by CAJames on 06/28/22 at 03:41:49 Re: caps. In normal operation they should drain within seconds of powering off the amp. Steve has said this several times, including just a couple days ago when he posted about fuses. If they still have a change there is a problem. IMO. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by will on 06/28/22 at 03:57:43 Not my experience. Lately working a lot on ZRocks, with my resistor draining wire/resistor rig I clip one side to ground, and the other, I touch to the hot side of a cap. Some of those caps are really close to the ground buss. If I accidentally cross the hot electro cap lead with the ground buss with the hot side of the drain wire, there is a notable discharge spark that always gives me a start. Whereas, just touching the hot lead, the resistor rig drains the energy on the way to ground on its other end, no drama. EDIT: Sorry CAJames. I was in a rush to get this post off... so brusk! I have been draining caps manually so long with modifications that I can hardly remember the early Torii times... starting something like 6 years ago. But I am pretty sure that before I got my resistor drain wire right, with too little resistance, I would get some light sparking at times when one end was clipped to ground, and touching the other to an electro cap hot side. And with more resistance and wattage rating for the resistors, no spark, the resistors presumably able to burn out the energy. But as I said, I have been so careful for so long, I think I recall some personal zaps earlier on in the Torii, but can't be sure. The CSP3 on the other hand, I have been zapped several times... mostly to do with the electro caps that are associated with the headphone jacks... but this, I suspect is a little different than the Torii, or the main power caps in the CSP3, these caps not so easily drained with no headphones hooked up??? But forget to drain them and touch them... not good! I am far from an expert on these things... just saying that in my experience, I think all three components have given me a zap or several. That said, maybe I am off in my guess that this SE34 in question would hold cap charge, my assumption. I am not familiar with the posts you mention from Steve. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by CAJames on 06/28/22 at 04:58:24 I think Steve was talking specifically about amplifiers, with power tubes. ZRock is designed to be always on and may (probably) work differently. But again, IMO. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by will on 06/28/22 at 05:08:43 Sorry, I was writing the above EDIT before seeing your post, but looks like we were on a similar wave length. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by dank on 06/28/22 at 12:33:01 Kedros - now that the amp is discharged, through you!, hook it back up to your system but don't plug the power cord into 120vac. Do the speakers buzz? If not, plug the amp into 120 vac but don't turn it on. Do the speakers buzz? If not, the problem is a high voltage capacitor in the amp that is taking a VERY long time to discharge and until it does discharge it causes the speaker buzz. Many times there is a resistor added to the design to discharge those big capacitors in a reasonable period of time and maybe that part got zapped. The fact that a capacitor can hold a charge big enough to zap you for minutes or 10's of minutes after being powered off is not unusual. I found that out at age 13 with a small guitar amp. I think that was the worst shock I've ever gotten in my entire electronics career. Dan |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Same Old DD on 06/28/22 at 13:15:13 Dan put it quite well, Kedros. It is a ONE step at a time thing you have to do in order to track this down. Maybe even more than once, because we miss things sometimes. Chasing noise in a system can be maddening! Good luck with this! Your issue has several of us on the edge of our chairs, because we have all been there and often each cause is unique, but the resolution can be a standard one. Thanks for having the courage to share this. You'll find it! |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Mannytheseacow on 06/28/22 at 14:05:00 Dylan, I had similar thoughts to Dans but haven’t contributed because I was just suspecting. For what it’s worth, ungrounded buildings are fairly common in my area. In my office if I get a cell phone near my computer monitors I get a similar issue as you describe with the hum. It took me a while to figure out it was because none of the outlets are grounded. Likewise, my home has all three prong receptacles but none have a ground attached. I had to physically run my own ground wire from the three prong outside to earth for any outlets I wanted to connect devices to that require it. So, could be a bad resistor or could be your ground. Both are worth checking. Good luck and keep us posted when you find the issue! |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Steve Deckert on 06/28/22 at 16:33:35 The SE34I.5 / 6 as well as the SE84 series amplifiers have a floating output stage. That means that the negative speaker post on the amplifier is not grounded. Actually on the SE34I.5 / 6 there is a high value resistor between the negative binding post and ground. The resistor is placed there so that when connecting a powered subwoofer you don't get hum. Some powered subwoofers expect a common ground between the two channels and without it will hum. The resistor gives the subwoofer amp what it wants. Without the negative speaker lead fully grounded, it means that when you plug a speaker into the amplifier it is possible with certain cables to create an antenna with a voice coil attached to it. In high noise environments, you would hear the audible noise, like 50/60 cycle hum, and the harmonics of it through the audio band. Try connecting the negative speaker jacks on the amplifier to a bolt on the top of the power transformer and see if the hum stops. Steve |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Kedros on 06/29/22 at 11:30:04 This community is great thank you everyone for all the help and advice! I didn't have much time to do any diagnostics after work yesterday and will be able to do more tonight but just an update. I had my amp sitting on my work bench for a little over 24 hours completely unplugged, no tubes, power cord, nothing. I proceeded to bring it back into my setup and hooked just the speakers up and nothing else. The noise was gone! At least I couldn't hear anything, however when I touch the amp anywhere, the hum comes back and if I touch the screw that holds one of the transformers underneath directly it gets louder. I would go back and forth with my fingers and the hum would change intensity when I switched between touching the frame and the screw. So I gotta rule it out as being an issue with the amp right? Steve, (it's an honour). I tried running a ground wire from the negative speaker jacks to the tops of the bolt on the power transformers and didn't experience any change. Also when I plugged the power cord back in the hum instantly comes back. Sorry if its a rushed post I typed it up before work this morning. More updates asap! Also going to try to post pics. Thanks Dylan |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by JBzen on 06/29/22 at 12:45:47 Quote:
What is the residue? Could it be dielectric leakage from a capacitor that is making a connection between the capacitor and chassis? Could a bleeding resistor have opened up causing slow drain thru the residue connection? I would open the amp up and examine for signs of overheated resistors or leaking capacitor. Use a plastic spoon handle to move items around in the amp to get better views of items in question. |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Kedros on 06/30/22 at 23:16:46 I just want to say thanks to everyone for all the help and suggestions it is very much appreciated!! Well I finally had some time to do some more trouble shooting and Steve, you where right. I had first attached the wire from the negative speaker jack to the top of the transformer bolt with no effect. But when I put it to the bottom bolt of the transformer that went into the chassis the hum immediately went away! It was weird too because its specifically those bolts holding it to the chassis. Well not weird, I just don't really know what the reason behind it is. So I took it down to the workbench to put a nice wire with a fork spade on it and ended up snapping a bolt :( Other than that tho I managed to get the wires on and introduced it back into my system hum free and I am currently listening to it with no issues! I will still be sending it in when I get my UFO25, but that's a different task for a different day. I am just happy I have my amp back and music for the weekend! Thanks Dylan |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Steve Deckert on 07/01/22 at 03:56:01 My fault, it is the bottom bolt on the transformer that lacks an insulator for vibration control, so that is why it worked... the others are what we call a hit and miss ground due to the nylon sleeve washers. Glad you found it! Happy Listening Steve |
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Title: Re: Low speaker hum/buz even when amp isnt plugged in. Post by Steve Deckert on 07/01/22 at 04:02:31 Well at least now we know that if the power grid is hacked and everyone is in darkness for weeks or years, you will be able to receive messages from space just by unhooking your ground wire : ). You can't get a much more zen receiver than that... an antenna connected to a voice coil on a loudspeaker. See, I really do have your back! -Steve |
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