[GrindingThud]

There are a couple of noise issues typical of the amp (or any similar OTL). The output tubes are notoriously noisy. Some hum, some fizz, some very microphonic, and some arc over on rare occasion. It took me a long time to find tubes that I liked and are quiet. The drivers also can be microphonic, hum, or fizz. It's not so much an amp design problem but more a 6AS7 otl thing. Once you find good tubes, stop rolling. Now, the amp does have a design that is prone to very low level hum, that is magnified by bad tubes. I did obsess over the hum because I was using sensitive low impedance phones not recommended for the amp. I ended up modifying the power supply and heater wiring in the amp to quiet it all the way down (described in the WA3 mod thread in my signature line). As far as the PS xformer goes, the amp draws very very different current when swapping to 5998 or 7236 tubes....the plate current actually drops almost in half, as does the heat. Flip side, I'm running constant current sources (like the speedball from bottlehead) and hold the current high and sometimes 6n1p 6CG7 and/or other tubes with higher heater current in the driver section The transformer can easily keep up. The amp has good bones.

 

[ctrlshift]

I pray to the tube gods during my ritual 2 min warmup and that seems to be helping. It seems more likely to make noises if I start running music through it too early.
 
I read somewhere else on these forums that the WA3 is a very tubey amp - the power tube does the work of an output transformer which explains why the more expensive amps don't have whine threads.
 
My wife reckons I wouldn't have been as entertained without a buzz to kill. Probably got a point. Makes the silence more satisfying. I am scared to touch anything now that I have finally got it silent - with a 1951 RCA 6AS7G no less... wasn't expecting silence from such a relic.

 

[hodgjy]

The WA3 is by the pickiest amp with respect to tubes I have ever come across.  I've owned other tubes amps and listened to a handful of others.  The pickiness is extreme.  Annoyingly so.  Because of that, I rarely listen to it anymore.

 

[volted]

  I'm not convinced the power transformer in the amp is very good.  Depending on which tube I put in the power slot, the transformer will change different temperatures and hum at different volumes.  Tightening the restraining bolt down did help a little with the hum.
 
These amps are quite simple.  The only active components in them are the tubes and the transformer.  Noises have to be coming from one of them.
 
Since it uses a toroidal transformer, you might have some DC in your power line.  Toroidal transfomers hate that.

 
Given that the noise stops for me with a tap on the power tube, that's probably the issue but the amp does seem fussy regarding tube pairings.

 

[hodgjy]

   
Given that the noise stops for me with a tap on the power tube, that's probably the issue but the amp does seem fussy regarding tube pairings.

The amp certainly is very fussy with tubes. It's the most fussy amp I've ever used or come across.