- 2012-08-15 8:24 am
I have thought for years that valve output transformers should come with coaxial cable leads for the high-voltage (primary) side. With the coax shield (outer braid) grounded, there would be much less chance that the signal here would be coupled back into earlier stages in the amp.
Reminds me of the first guitar amp that I build. Nasty squeals when turning up the volume of the lead channel.
The guy that I got the transformers from (an old valve PA amp builder at the time) told me to use coaxial television cable to shield the large voltage swings. Connect the shield to HT so there is no(t much) dc voltage between the core conductor and the shield.