[samplesj]

I've got a mechanical buzz from my current UCD400/TX-102 integrated.  I am almost positive that it is coming from the transformer itself.  It doesn't make any noise in the speakers at all, just the normal transformer shaking/buzzing.

I'd suspect DC, but as a test I've tried it after a BPT3.5sig balanced power transformer so it shouldn't be passing any DC right?

Also, originally I built this testing as just the UCD400 and it was quiet after turn on.  It had a loud buzz cycling down to silence.  This is where I think I've messed it up.  When I rebuilt the amp I went ahead and REALLY tightened the mounting bolt because I was trying to get rid of the startup see-saw buzzing.

Is it possible I damaged the transformer?  Or maybe did I just compress the foam too much and need to replace that.  I've got a huge box of cork underlayment and I found a few comments around the web about using that as physical isolation.  Would the cork be safe to use as the vibration dampner/spacer between the transformer and the chassis?

[ScottMayo]

I've got a mechanical buzz from my current UCD400/TX-102 integrated.  I am almost positive that it is coming from the transformer itself.  ...
Is it possible I damaged the transformer? Or maybe did I just compress the foam too much and need to replace that. I've got a huge box of cork underlayment and I found a few comments around the web about using that as physical isolation

Some transformers just buzz. I had an earthquake supernova subwoofer with a transformer buzz that was audible across a room. I made them replace the tranny, bolted it down firmly, and things got a bit better.

I don't like cork in circuits, myself. Cork can char. A transformer shouldn't get that hot, but why risk it?

[samplesj]

Some transformers just buzz.

But previously this one didn't.  It took me a while to sell off enough of my old gear to buy the TX-102s from John at Bent so I ran the UCD400 as a normal amp for a month or so.  It did do the startup ZZZZ ZZZ zz z and then it was quiet.  Now it doesn't do the start up varying, but its a constant zz level.

I don't like cork in circuits, myself. Cork can char. A transformer shouldn't get that hot, but why risk it?

Charring or other risks is exactly what I was asking for.  Thanks for the heads-up.

As a way to make sure its not just an overly compressed foam washer I may cut a piece of cork and put it in long enough to test.  With me standing right by with the power cord in hand it can't do too much damage.

[andyr]

I've got a mechanical buzz from my current UCD400/TX-102 integrated.

I'd suspect DC, but as a test I've tried it after a BPT3.5sig balanced power transformer so it shouldn't be passing any DC right?

Also, originally I built this testing as just the UCD400 and it was quiet after turn on.  It had a loud buzz cycling down to silence.  This is ...

Hi Jeremy,

Actual mechanical buzz as I understand it is caused by DC on the AC line ... so I don't know what you can do to remove/attenuate this.

However, as a matter of course, I believe it's a good idea to minimise the transfer of any transformer vibration (whether this is audible as a "buzz" or not) to the case by putting a piece of 6mm Sorbothane underneath toroids ... and then not screwing the nut on the retaining bolt too tight.  In fact, I use 6mm nylon bolts instead of steel to provide a little "play" (and also remove some iron from inside the toroid magnetic field).

Regards,

Andy