Anybody knowing this circuit?

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L´Andratté

Well-known member
Joined
Jan 17, 2013
Messages
793
Location
Hamburg Germany
Found it on some 3rd sublevel of the web rather closed down looking site but sure
looks interesting. Since I happen to have some BS170s around I will try it next days.
The author is promising a lot here ;)
http://gabevee.tripod.com/sstubepre.html

Maybe somebody is inclined to comment on it? :p

And BY THE WAY anybody knows what THIS is(below)?  Scavenged it of some wrecked DUAL CV31...looks like some poisonous insect??? Exotic capacitor???
DSCN3513.jpg

 
L´Andratté said:
Found it on some 3rd sublevel of the web rather closed down looking site but sure
looks interesting. Since I happen to have some BS170s around I will try it next days.
The author is promising a lot here ;)

Maybe somebody is inclined to comment on it? :p

And BY THE WAY anybody knows what THIS is(below)?  Scavenged it of some wrecked DUAL CV31...looks like some poisonous insect??? Exotic capacitor???

Edit: picture won´t show...
 
For my second semester analog course, we made RIAA preamps using BS170. It can sound good..

This circuit only uses the MOSFETs as source followers, that is with full voltage feedback. This is not the way to get the simplest distortion behavior.. That would be undegenerated common source..

This circuit could be prone to LF instability (motorboating) with 3 poles inside the feedback loop... IDK, though.. Might be fine.

The 10k in the drain of the input FET doesn't do anything but increase input capacitance...
 
He!
I built this today (exactly as proposed but with 3904) and: nothing...
After thinking, some reading (I´m new to MOSFETs) & tweaking the usual suspect components: fuzz...hmmm, well, and I had
hoped for the hidden treasure- ::)
And now your comments, thanks for the replies nonetheless!

Regarding the mysterious components: I think they were not from DUAL but from seventies answering machine called
ALIBIPHON, are they some kind of inductors, mini-relays? I don´t know, very curious so if someone knows, please tell me!
 

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L´Andratté said:
Maybe somebody is inclined to comment on it? :p

I spent some time simulating this on the weekend, and if the sim is even vaguely in the ballpark of the operation of the actual device (I think is it), then this is an absolutely terrible design.

Huge distortion (nothing like what's claimed in the article) and when clipping occurs it's absolutely and utterly hard-brick wall clipping on one side of the waveform.

The author is flat out lying.
 
some quotable material:
This was the holy grail of NFB applications, because it cleaned the sound up extremely. It also made the wave output more tubelike, and clips softer. Mind you, this is just a regular old application of NFB. And a very small amount at that.
Yet the sound is so clean, so imagey, so warm that it is amazing. As one person put it, "you hear more of the music". It is as clean as any tube amplifier. And almost as warm (one can make a tube amp sound very warm)....
 

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