Thoughts on this preamp design?

Anyone technical have any thoughts on this?

Is it a first as he says?

If it varies the gain why is there also a volume knob? My impression was that it would only vary the gain and work differently to a usual pre.

No idea but @Adpully had a Transcendent OTL power amp IIRC.

It does make sense to have just enough gain so you’re not burning it all away with the pot. You’d still need the pot for fine adjustments, I would have thought.

The issue with some pre-amps that vary the gain is that the sound may not be exactly the same at all volume levels. I know that Guy measured TVCs and found this to be a problem; obviously this is totally different tech but it could still be an issue.

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Makes sense. I find it interesting anyway.

Variable mu valve in a line stage? Ta but no.

Yeah I like that this kind of thing is tried

Quite. This is not particularly new, remote cut-off tubes were developed for automatic gain control circuits, back in the day. It works, but the penalty is high distortion.

The innovation here is in marketing/being daft enough to use them for a preamp rather than an effects box.

My audible illusions pre has two knobs on the front to adjust the gain, plus a volume control. It sounds great. I find the adjustable gain really useful to adjust / improve the sound.

Is that using a transformer?

It’s not a passive preamp, if that’s what you mean. Mine uses 2 Russian valve 6922 equivalents. It’s also zero feedback.

I think I can improve the sound quality by using different gain settings. It sounds better when adjusted. I try and use less gain and more volume. That’s a rough rule that varies according to the source and even perhaps the recording.

It was once a Class A Stereophile rated component.

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You remember correctly It was a brilliant thing -I should have kept it.