A Heretical Unity gain line stage

[skyraider]

In any case, the f3 of the specified transformer is 80-100kHz. Here's the datasheet:

In that case, its fine.

Keep the updates on the listening results!

[SY]

I had this version in my living room system for a week or so; it sounded fine. If it did anything other than silently and effortlessly raise and lower the volume, I could not hear it. Getting the system silent unless spoken to was quite worthwhile.

Since than, I've been living with the Mark 2 version (article coming soon), with an output servo, but identical signal and regulator circuitry to what I'm showing here. I've spent this afternoon with a glass of something alcoholic (ok, maybe more than a glass), kd lang, They Might Be Giants, and of course, Tony Rice, as my wife has given me an afternoon off to celebrate Father's Day in the US. The preamp does its job with effortless grace.

Version two, also with a servo, but with RCRC filtration on the plates and some Ampex input transformers, is running my garage/lab system. That's been getting some workout as I try and get the Mark 3 (with novel servo) boxed up and ready for some extended listening.

I should mention that, claiming moderator's privilege, I've been incorporating revisions in the original posts.

[analog_sa]

boxed up and ready for some extended listening.

If i may be brave and jump the gun with a prediction - it will "silently and effortlessly raise and lower the volume" and be otherwise utterly indistinguishable from any other well designed preamp

Mark 3? Just giving the silver wire pushers more business.

[SY]

Originally posted by analog_sa


If i may be brave and jump the gun with a prediction - it will "silently and effortlessly raise and lower the volume" and be otherwise utterly indistinguishable from any other well designed preamp

If all goes well, yes. Novelty can have negative consequences... But the version I'm listening to is quite distinguishable from several others I've tried- it doesn't pass along the buzzes, bamgs, and burbles from the lousy grounds that I can't control.

[wrenchone]

Not a rag at all, just an innocent question - why did you choose your current approach rather than something like a White follower? I've used both the White-type follower and a simple current source loaded follower with JFETs and gotten decent results.

[SY]

Don't worry about the rag!

A White follower, done correctly, will work fine. It will require twice as many tubes and elevated heater supplies, while giving essentially no better performance. And it is much tougher to direct couple- which will be the next chapter in this saga.

My previous preamp also used JFETs as cathode loads. It worked well enough for me to use it for 20 years or so.