MikeB said:
No, I did not mean shunting by a resistor with negative resistance. I am speaking of "shunting" VAS stage on the load, across a symmetrical voltage follower with gain close to 1, but less than.
Hi Mike.
Sorry for not being clear. Ok, closed loop distortion vs. VAS loading R. Distortion does not change until R becomes small enough to impact 10KHZ gain and then lower order harmonic distortion increases ( in proportion to the gain loss) and higher order harmonics remain roughly unchanged. As gain progressively drops, more harmonics increase. No matter how I look at it, distortion with VAS loading gets worse when the gain drops at the frequency being tested. Total distortion is lowest when OL gain is highest.
Bill
Sorry for not being clear. Ok, closed loop distortion vs. VAS loading R. Distortion does not change until R becomes small enough to impact 10KHZ gain and then lower order harmonic distortion increases ( in proportion to the gain loss) and higher order harmonics remain roughly unchanged. As gain progressively drops, more harmonics increase. No matter how I look at it, distortion with VAS loading gets worse when the gain drops at the frequency being tested. Total distortion is lowest when OL gain is highest.
Bill
Thanks Bill, the info i wanted. Of course rloading needs to be reasonable, otherwise feedback seizes to work.
The important point was, as long as rloads are not excessive, closedloop distortion does not really change.
What rloading does to the sonics is a different story.
At which size of rloads did the performance degrade ?
Mike
The important point was, as long as rloads are not excessive, closedloop distortion does not really change.
What rloading does to the sonics is a different story.
At which size of rloads did the performance degrade ?
Mike
Max gain is about 133 dB and gain at 10KHz is about 103dB. Total VAS loading of 65K drops gain to 103dB from <1Hz to 10KHz. Anything smaller than 65k and 10KHz distortion starts to rise ..... lower order harmonics first. At 35k total VAS loading the amplifer is flat from <1Hz to 20KHz and there is significant second and third harmonic increase at 10KHZ. I did not check other frequencies to see what was hapening. If lower order distortions are significantly increasing, then maybe that is why it sounds good.
Bill
Bill
main transformer(changed to 15V as opposite to the early 18V):
An externally hosted image should be here but it was not working when we last tested it.
Sounds great,as long as you don't care much about the DC offset drift,think better to fit with a servo circuit.
You can try with any LATFET you like.🙂
You can try with any LATFET you like.🙂
Hello,
I discovered your design today and did you know it looks quite a french design from quite a long time ago called "Zenquito".
http://pagesperso-orange.fr/jm.plantefeve/sche.html
I didn't dissect the values of the components but it's a similar global scheme.
Some on this forum complained about the sound of the Zenquito but I always loved it, relaxed and not overly analytical in the bad sense of the term. Yours must sound quite good too.
I discovered your design today and did you know it looks quite a french design from quite a long time ago called "Zenquito".
http://pagesperso-orange.fr/jm.plantefeve/sche.html
I didn't dissect the values of the components but it's a similar global scheme.
Some on this forum complained about the sound of the Zenquito but I always loved it, relaxed and not overly analytical in the bad sense of the term. Yours must sound quite good too.
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