Building a Williamson EL34 amplifier

[KatieandDad]

What did you order?

Risky, I know. But I couldn't get genuine Sowter transformers.

Freeshipping 10K:10K permalloy audio isolation transformer with shield balanced and unbalanced conversion audio isolator|Transformers| - AliExpress

I don't think they will be fakes, copies maybe.

 

[baudouin0]

try a 10R+100nf in parallel partial ground lift.

 

[wg_ski]

Fifty bucks for an unknown quantity? Hammonds are only $65, and you at least know they’re going to be good. I used them on my 6550 amp and they’re perfectly transparent.

I also got some of the $6 Triads for a couple of different projects. If you drive them from a low Z source (like typical pro audio gear) they go *way* lower than the “rated” 200 Hz.

 

[KatieandDad]

try a 10R+100nf in parallel partial ground lift.

It's got a ground lift already.

 

[KatieandDad]

I've just got around to fitting the 10K:10K input transformers.

The amplifier is now virtually silent. There is an absolutely miniscule hum audible if you put your ear right against the speaker.

 

[baudouin0]

super

 

[KatieandDad]

If you recall, I also had an issue with massive hum with no inputs connected. That issue has been cured with the input transformers.

It no longer hums with no inputs connected.