Not really understanding what your saying. I have built a few sta levels point to point & only ever needed the trim on the 6v6's
That's nice of them to collaborate with you.This page describes the approach taken by Manley Labs. I've gotta say, I was blown away by the response to my initial enquiry about getting some boards. I got a very quick reply from the company's president, EveAnna Manley, who put me in touch with the parts department and we went from there. Amazing support for a humble DIYer!
Manley Labs T-Bar
...The 5670 equipped Variable Mu's were well received, and retained many of the characteristics that made the original version of the Variable Mu® popular. They did sound different than the original, especially when pushed past 6db or so of limiting..
Didn't realise you were using a pcb. It should work, try it out, see if it works, that's what I do. It can't be difficult to bypass if it doesn't.
Is there a trim also on the 6V6?
I agree. it was a strange choice. The 5670 is certainly a good tube, and mostly overlooked for audio despite there still being decent quantities of GE NOS available, but it's not a variable mu tube. At least not to any extent that an E88CC or a 12AU7 could also be a variable mu tube.make production units with the 5670, which only looks like a 6386, and is quite incorrect
so, in my mind, the question arises:
If it's so easy to make a compressor circuit using normal pentodes, why wasn't this common practice in the tube days? Surely there must be an advantage to using dedicated tubes?
...or was it? I haven't found any articles.
What is actually the exact process for the pushpull balance setup for STA? Injecting high level 1khz sinewave until the amp starts distorting then matching the AC voltages on cathode and anode?If you find a good match for the 6ba6 pair you can normally null any slight thumping with the balance trim on the 6V6's