Re: Re: Hawksford error correction
Well...yes it is, but as the feedback is applied to a less than unity gain output stage, it could be seen as a servo amplifier, but whatever it is called it does greatly improve the transfer linearity of the output stage without attempting to deal with this via an overall feedback loop.
Nelson Pass said:
Well...yes it is, but as the feedback is applied to a less than unity gain output stage, it could be seen as a servo amplifier, but whatever it is called it does greatly improve the transfer linearity of the output stage without attempting to deal with this via an overall feedback loop.
I'm with Nelson on this one. The term feedforward is bandied around a lot in ways which aren't justified, IMO.
I think one could be justifiec in calling something like the Tekronix CASCOMP differential circuit a type of feedforward error correction; nested feedback loops don't count; calling it feedforward is just window dressing.
~Jon
I get confused about this as well, but I am pretty sure that it is NOT feed-forward. It is a local amplified feedback loop that might have some intrinsic advantages. I have never tried it, myself, but with a rock band power amp, it might be just the thing.
The reason for this is because, IF you have a fairly high crossover distortion (open loop) in the output stage, then this may be just the circuit to fix it, before applying overall feedback, if you wish.
My colleagues, Nelson Pass and Charles Hansen, apparently have tried it, and Charles, at least, doesn't like it much. This is a disappointment, but oh well, we just have to keep trying for better audio quality. ;-)
The reason for this is because, IF you have a fairly high crossover distortion (open loop) in the output stage, then this may be just the circuit to fix it, before applying overall feedback, if you wish.
My colleagues, Nelson Pass and Charles Hansen, apparently have tried it, and Charles, at least, doesn't like it much. This is a disappointment, but oh well, we just have to keep trying for better audio quality. ;-)
This circuit I'm using in my amps more than fifteen years ( Thanks Mr. Hawksford, Thanks Mr. Cordell 
) and I highly recomend it. If is this circuit used, distortion fall more than five times. With 2SK 134 / 2 SJ 49 was measured distortion ( Ap ) less than 0.05 % on 100 kHz, 1 dB below clipping, which is for every Ayre's and Pass's only border of dream .
) and I highly recomend it. If is this circuit used, distortion fall more than five times. With 2SK 134 / 2 SJ 49 was measured distortion ( Ap ) less than 0.05 % on 100 kHz, 1 dB below clipping, which is for every Ayre's and Pass's only border of dream .
Upupa Epops said:This circuit I'm using in my amps more than fifteen years ( Thanks Mr. Hawksford, Thanks Mr. Cordell
They will argue that distortion is of no importance
Just one photo from the non-competent Czech designer (me) from the HighEnd 2004 exhibition in Prague, the preamp displayed is mine and was chosen for presentation of Wilson Audio Sophia:
An externally hosted image should be here but it was not working when we last tested it.
Music vs distortion
In any note composition is written anything about distortion. I am very surprised, that John Curl, designer which is known by his constuction with very low distortion, defend oposite ones .
- is it friendship with " old giants " ? I'm listener of music and distortion ruin the music, not upgrade. Change this view at last, it comes from people, which don't know make amp with low distortion and amp is amp, not musical instrument.
In any note composition is written anything about distortion. I am very surprised, that John Curl, designer which is known by his constuction with very low distortion, defend oposite ones .
- is it friendship with " old giants " ? I'm listener of music and distortion ruin the music, not upgrade. Change this view at last, it comes from people, which don't know make amp with low distortion and amp is amp, not musical instrument.
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