John Curl's Blowtorch preamplifier

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Re: Re: Re: Multi Layer Ceramic Cap measurements

1audio said:


Geez, my 7A22 is all discrete.

John mentioned a particular opamp, I'll get one from him and build another fixture. At 20 KHz 120 dB suggests an exceptional balance in the associated components. And a small stray component could throw everything off. 1 part per million is very difficult to get in a stable way, suggesting 10 uV in 10 V.

So are mine. You can't get inside and tweek the attenuator compensation without a lot of work. The in-amp circuit allows you to tweek away. BTW those resistors inside do 20V p-p at -130dB distortion and are very "thin".
 
scott wurcer said:


A while back someone mentioned no GNF, this is a far cry from totally open loop after all degeneration is feedback .... 🙂


Any amp driving a load can be considered as using feedback by this definition. In fact, that is feedback as it prevents the amp from putting out infinite current.

You win. I did have a load on the amp when I measured the THD.
 
Steve Dunlap said:



Any amp driving a load can be considered as using feedback by this definition. In fact, that is feedback as it prevents the amp from putting out infinite current.

You win. I did have a load on the amp when I measured the THD.

Steve, you used to fight harder when you were young, I guess...😀

http://www.youtube.com/watch?v=EwrnzezP5Ic

Jan Didden
 
Steve Dunlap said:



Any amp driving a load can be considered as using feedback by this definition. In fact, that is feedback as it prevents the amp from putting out infinite current.

You win. I did have a load on the amp when I measured the THD.

Just the old feedback joke Steve, actually your circuit is nice. At least what I saw would qualify as power gain not voltage gain per-se maybe that is a source of confusion.
 
janneman said:


Steve, you used to fight harder when you were young, I guess...😀

http://www.youtube.com/watch?v=EwrnzezP5Ic

Jan Didden


That is not me, but yes I did fight harder when I was young. I still fought harder when I was old until I became a quadriplegic. That takes a little of the wind out of your sails.


The amps mentioned in this review are mine. Either Tom or the reviewer got some of the info on the amps wrong. I wasn't there to correct it.

http://www.soundstage.com/masz02.htm
 
scott wurcer said:


Just the old feedback joke Steve, actually your circuit is nice. At least what I saw would qualify as power gain not voltage gain per-se maybe that is a source of confusion.


I got the joke, but since some have made up their minds I did use feedback I thought I might as well admit it and get it over with.

I think the source of confusion is that I used a different voltage gain amp than what I have posted so far. I was using a modified version of the power gain stage I posted. I'm new here. No one knew who I was (although I have met and talked with many of you) so I was starting out slow. I couldn't post everything I ever did in the first few posts.

I do appreciate that you say the circuit is nice. Thanks.
 
Hey John,
Check out that Krill thread...Ive been over there all afternon myself!
Note that it is not in any way related to Krell..

If I remember correctly, krill is whale and fish food, including plankton, and is the base of the food chain on the oceans. There may be a double meaning or some sort of pun hiding in there, perhaps not, but I am always looking for such word-play.

The Krill amp is a steroid laden version of the classic bipolar line level diamond output buffer topology, just scaled up to higher voltage and current. Conveniently, the Krill output stage is more or less separate from the input voltage gain stage, meaning it may have some interesting adaptability, with assorted front end gain options, even with tubes discussed in the thread.

Not discussed in the thread is the concept of using a full differential balanced tube front end coupled to a pair of the Krill outputs, as a single channel balanced differential power amplifier. You could use the less costly +- 25 volt version, and by being internally self bridging, get some huge power outputs even with moderate supply rails. Same holds true for adapting JCs famous folded balanced differential topology in J- FETs, providing differential drive to a pair of these....Here we go..I gotta build a pair!!! :bigeyes:

Woff, AND Howl! [ If you hang around long enough, your GONNA learn SOMETHING new!]
 
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