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Hum in a transformer (Read 4712 times)
jsm71
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Hum in a transformer
12/08/13 at 16:13:41
 
Just in the last couple of weeks I've starting noticing an audible hum that I can only attribute to a transformer.  I can hear it in the left channel.  If the right channel is doing it also it is so faint that it is not a bother.  I swear that when new the amp was totally dead quiet when turned on.  This has just cropped up.

I know I need to call Steve and I will this week, but I was wondering if I should expect it to go away with time (since it is only recent) or if anyone else is experiencing this.  This is my first Decware piece and I don't know what is normal with this gear.  My listening room is very quiet and I can hear the hum across the room, albeit at a low level.  Naturally when the music starts it doesn't matter, but it bugs me.

Scott
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« Last Edit: 12/08/13 at 16:14:13 by jsm71 »  
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Lonely Raven
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Re: Hum in a transformer
Reply #1 - 12/08/13 at 17:50:40
 

Can you lessen it by putting your hand on it? Is it a physical hum or electrical hum?

I'm just curious really, I don't have any solutions for you.

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jsm71
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Re: Hum in a transformer
Reply #2 - 12/09/13 at 16:12:12
 
I'll try tonight to see if touching it has effect but it sounds like a classic transformer hum, similar to the sound flouresent light transformers emit.  I have also determined that the sound is cumulative from both channels, not heavy on one side as I first thought.  I have also tried swapping rectifiers and that didn't change anything.

It is a minor annoyance but I need to know how much I should be concerned.  My question stands to all Decware owners; do you hear the transformers on your amp?  Honestly, I've never seen a transformer that didn't generate some hum.  It's just a question of degree.  If it is normal for tube amps to have this ok, I can accept that as part of the deal.  If they are supposed to be dead quiet than I have an issue.
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« Last Edit: 12/09/13 at 16:34:52 by jsm71 »  
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Lonely Raven
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Re: Hum in a transformer
Reply #3 - 12/09/13 at 17:30:27
 

Electrical hum is usually dealt with in the design stage. If the layout of the transformers is good, you shouldn't hear that fluorescent ballast buzzing. That's Amp Building 101, layout of the transformers, and I'm sure Steve has that down. So unless there is an issue with the transformer it shouldn't be a problem.

Now, you could still have physical vibration simply from the current flowing through those parts. If you put your hand on it and can make the noise go away, something simple like a physical damper for the transformers is an option. Something like the Herbie's SuperSonic Stabilizer can help. http://herbiesaudiolab.net/stable.htm

Once you know more and can accurately describe the problem, call Steve, I'm sure he's got things you can check to possibly solve this.

In guitar amps I've had failing tubes or other parts cause an electrical imbalance that makes transformers resonate, so don't put it off as it could be a small issue that could turn into a bigger one.
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jsm71
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Re: Hum in a transformer
Reply #4 - 12/09/13 at 19:00:32
 
Thanks for the ideas.  I will definately try to see if physical damping helps.  That would be an easy fix, not that I should have to, but I won't complain if that is the remedy.
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Lonely Raven
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Re: Hum in a transformer
Reply #5 - 12/09/13 at 21:40:46
 
I agree, you shouldn't have to; that's why I feel once you narrow it down a bit more and feel you can describe it, give Steve a call. There are so many things that can cause transformers to make noise...I'm betting even bad power (harmonics in the 120v line) could cause noise in the transformers! That's not something an amp builder would be responsible for (as an example)

As with all issues, divide and conquer till you narrow down what the issue is.
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« Last Edit: 12/09/13 at 21:42:22 by Lonely Raven »  
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will
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Re: Hum in a transformer
Reply #6 - 12/11/13 at 01:28:58
 
Power can definitely contribute, but if it was consistently quiet before, and now consistently noisy...this looks like a pointer that something changed. It could be your utility power that changed though...right.

But the fact that it is strong on one side is another pretty good pointer.

It is not only the rectifiers that could cause a 60 cycle hum...I would trade channels on each tube type, one at a time and see if it changes sides. Might be a bad tube, besides rectifiers (that seem fine) especially inputs and power tubes, but I would check the VRs too if it is not the power or inputs.
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jsm71
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Re: Hum in a transformer
Reply #7 - 12/11/13 at 13:36:39
 
I have discovered that the hum is not coming just from one side.  It is cumulative.  I was confused because of the power up sequence.  I always turn on the right channel first, then the left.  When I tried doing it in reverse order now the right channel seems to add the hum.  Reality is that both are generating some noise and it just gets louder when I turn on the second channel.

I do need to talk to Steve.  Maybe some further line treatment is needed.  I don't put the amp through any conditioner.  I have a PS Audio Quintet which is super for my sources and preamp, but I have always read to not use one for the amp.  I go straight into the wall.  Odd however that this seems to have just started a couple of weeks ago.

Putting my palm on the transformers had no effect.  This is internal electrical hum.
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« Last Edit: 12/11/13 at 13:38:40 by jsm71 »  
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Lon
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Re: Hum in a transformer
Reply #8 - 12/11/13 at 14:17:33
 
j,

I have always read that about conditioners too. But I think the Duet, Quintet and the regenerators from PS Audio are different. I have Duets, and had a P300 (well, still have it inoperable) and a Power Plant Premier and all give benefit to an amp plugged in to them, and does not restrict dynamics, etc. So I would say feel free to plug it in and try it. I'm not certain that it WILL quell the hum, but you're not imo going to restrict the sound by doing so. I've always found these products to improve the sound. Your mileage may vary, of course, but well worth a shot. They do make the sound different. . . and when I adjust and then compare I consider it a valuable improvement
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Lonely Raven
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Re: Hum in a transformer
Reply #9 - 12/11/13 at 16:56:07
 

Yeah, not all power filters/conditioners/regenerators are the same.

The first point is that the device first needs to be able to handle the constant current of your amp, but the key point is that it need to be able to handle the amps sudden current demands, and do so without being sluggish about delivering that inrush of current. That's where the power device can and will effect the sound.

PS Audio seems to have a grasp of this, and it can't hurt to try it assuming the device can handle the constant current. It would also let you see if that filters out the problem!
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jsm71
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Re: Hum in a transformer
Reply #10 - 12/11/13 at 19:09:20
 
Thanks for the encouragement.  I no sooner posted my last response that I thought, hey, why not try it?  It clearly cleaned up the power for everything else.  The Quintet also has a marked outlet just for the amp.  I don't know if that really means the outlet is wired differently or if it is just "labeling".  PS Audio seems to know what they are doing however.  

My prior amp put out 900 watts/ch @4 ohms and had a regulated power supply, very unique and designed specifically for varying impedance swings.  The manufacturer was clear about not using a conditioner for this amp.  I think Steve's voltage needs may not be so severe.  It is certainly worth a try.  That will be on tap for tonight.  Before trying that I think I may also just try swapping outlets or using the amp on a dedicated outlet with nothing else.  It shares an outlet currently.
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Lon
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Re: Hum in a transformer
Reply #11 - 12/11/13 at 19:30:41
 
I know you'll update us. . . .
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Lonely Raven
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Re: Hum in a transformer
Reply #12 - 12/11/13 at 20:58:54
 

Yeah, I'm super curious to hear what your further testing shows up!

Also, I believe those outlets on power conditioners and such that say they are OK for amps, I think they have *less* filtering so it doesn't muck with the current draw of the amp. But *some* filtering might be just the right amount for you.



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jsm71
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Re: Hum in a transformer
Reply #13 - 12/12/13 at 13:31:03
 
I played around with different power outlet options last night.  Good news and bad news.  The bad news is I couldn't eliminate the hum.  It would likely not be noticable or less so in a larger room, but my space is small and very quiet.  

The good news is I now have the amp plugged into the amp outlet on my Quintet.  That helped the sound quite a bit.  I didn't think the degree of transparency could rise any more but it has.  The bass has also tightened noticably.  One advantage of this problem is I never would have tried the conditioner based on my prior thinking.  Nice lift.

I was listening to John Mayer's Gravity on his live Where the Light Is 4 LP set.  This is a super engineered recording, heavily center focused on many of the numbers.  Simply amazing realism and I highly recommend this if you like Mayer's music.  The set was $80 for the 4 180 gram LPs, but worth it.  I was guilty of audiophile focusing on the sound more so than to the music.  So clean, clear, and in the room, it was scary.  I could live with the hum I guess, but I know its there.  Talking to Steve will be the next step.  
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« Last Edit: 12/12/13 at 13:36:45 by jsm71 »  
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Lon
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Re: Hum in a transformer
Reply #14 - 12/12/13 at 13:35:19
 
Glad you checked out using the amp with the Quintet! I was pretty sure it would be a positive step.

I think yes, call Steve. Just be sure you don't talk to him more than a few hours and delay his getting to Stone and Raven's (hey some sort of diabolical law firm?) ZMA builds. Wink
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