[TheMarchingMule]

Switched left and right tubes, replaced rectifier with a totally different model, same result. When the WA6 is initially powered on, there's a loud hum/buzz on the left side, that drops off sharply after a few seconds, but when I turn off the amp, it's noticeable that there was still some hum going on, compared to the silence that I now hear.
 
It doesn't increase with volume, and it can be masked with music. I'm using Grado RS-1i w/ the WA6 low impedance switch, so I'm still wondering what's causing this, and especially why just one side. I'm guessing the problem is within the amp, and so I should contact Woo Audio about this?
 
Thanks in advance for the guidance.

 
EDIT: Hm, flipping the impedance switch does nothing, either to the hum, or the volume. Is it possible that it's broken?

 

[cifani090]

I think its normal, just part of the starting up of the power transformer,etc. I get the same think with my 1250.

 

[Sundance]

It's common for tube amps to have a powerful hum when they are turned on. However, it comes from both channels and is very brief. You may want to ask the legions of woo owners here. Another troubleshoot is to disconnect it from your source and power on just the amp with the headphones.

 

[Uncle Erik]

I'd guess a cap is faulty or heading south on the left side of the power supply.  It's probably letting a little AC through; I'd look into having it replaced.

 

[TheMarchingMule]

Quote:

I'd guess a cap is faulty or heading south on the left side of the power supply.  It's probably letting a little AC through; I'd look into having it replaced.

That does seem to be the problem. I quoted you on the email I sent to Woo Audio.

 

[Uncle Erik]

Caps do that. And it should be pointed out that this isn't Woo's fault or a design flaw.