Sound Quality Vs. Measurements

[DF96]

Originally Posted by dvv

I am not sure just how much can one actually hear this or that CCS design, if you mean CCS as a part of a say differential circuit. In that case, a CCS is sort of an auxilliary ciruit, necessary for proper operation of the key, or primary ciruit.

CCS quality can have a major effect on common-mode distortion. For the 'standard' opamp-like power amp the CM-mode distortion has a big contribution from the LTP CCS non-linearity, and no amount of NFB will remove it. A simple tail resistor could be better than a really bad CCS.

CCS elsewhere in the circuit are within the NFB loop so probably won't be heard.

[nigel pearson]

How about old fashioned bootstrap CCS to VAS ? These days the capacitor costs more than a transistor CCS so is not the likely choice . Bootstraps are useful when driving MOS FET 's . I have a circuit of a double bootstrap for MOSFET's somewhere . I use a cheap voltage doubler and regulator to do the job and conventional CCS if wanting the last once of MOSFET power . I have found to take the voltage down to main rail level still has advantages if wanting nice clipping ( switch ) . MOSFET have slightly less than 80 % voltage gain typical when used as output stage current amps .

A tail resistor with clean fixed supply is OK . I think I saw someone do a stimulation on this , he was shocked how good a tail resistor was . Common mode rejection was about 90 dB with a tail resistor and 130 dB with the optimum CCS as John showed some time ago . I think most valve circuits never get near to 90 dB .

[a.wayne]

Originally Posted by dvv

Wayne, old buddy, I can't open any of the video links you supplied.

Not sure why , they are youtube links ..

[benb]

Originally Posted by a.wayne

Not sure why , they are youtube links ..

The links were to the mobile site for youtube. Deleting the "m." part of the URL makes it look like the "regular"youtube site:
Audiophile Paradise at Tokyo Audio Show
http://www.youtube.com/watch?feature...&v=vWHqieSrSaQ
News report, about what one would expect. I'd like one of those turntables...

The Vagabond Soles @ Blackbird Studio
http://www.youtube.com/watch?feature...&v=peCF0gwTWoE
OMG, it's full of diffusers!

[dvv]

Originally Posted by benb

The links were to the mobile site for youtube. Deleting the "m." part of the URL makes it look like the "regular"youtube site:
http://www.youtube.com/watch?feature...&v=vWHqieSrSaQ

Thanks for the pointer, Ben.

[bcarso]

Originally Posted by benb

OMG, it's full of diffusers!

That was actually the last thing that Dave Bowman said before he was sucked into the the monolith.

[dvv]

Originally Posted by bcarso

That was actually the last thing that Dave Bowman said before he was sucked into the the monolith.

Yeah, but man, what a ride!

Odd you should mention that, I've just started reading Arthur C. Clarke's "2061: Oddisey Three", the final chapter of the trilogy.

Jeez, when I remember how struck by the original movies I was ... I saw it in March 1971, in New York.

It made a convert of me, of sorts. After that, to this day, I have gobbled up a respectable number of SF books by everybody who was anybody from the '40ies onwards. Always loved that eternal question: what if?

Like Dual (1019 turntable) and Uher (tape deck) made me an audio convert.

[bcarso]

Originally Posted by dvv

Yeah, but man, what a ride!

Odd you should mention that, I've just started reading Arthur C. Clarke's "2061: Oddisey Three", the final chapter of the trilogy.

Jeez, when I remember how struck by the original movies I was ... I saw it in March 1971, in New York.

It made a convert of me, of sorts. After that, to this day, I have gobbled up a respectable number of SF books by everybody who was anybody from the '40ies onwards. Always loved that eternal question: what if?

Like Dual (1019 turntable) and Uher (tape deck) made me an audio convert.

Yes, and Bowman's quarters during his captivity could have used some acoustical treatment, and not just diffusors But whaddya want: superintelligent aliens can't think of everything.

[tvrgeek]

Originally Posted by nigel pearson

How about old fashioned bootstrap CCS to VAS ? These days the capacitor costs more than a transistor CCS so is not the likely choice . Bootstraps are useful when driving MOS FET 's . I have a circuit of a double bootstrap for MOSFET's somewhere . I use a cheap voltage doubler and regulator to do the job and conventional CCS if wanting the last once of MOSFET power . I have found to take the voltage down to main rail level still has advantages if wanting nice clipping ( switch ) . MOSFET have slightly less than 80 % voltage gain typical when used as output stage current amps .

A tail resistor with clean fixed supply is OK . I think I saw someone do a stimulation on this , he was shocked how good a tail resistor was . Common mode rejection was about 90 dB with a tail resistor and 130 dB with the optimum CCS as John showed some time ago . I think most valve circuits never get near to 90 dB .

Exactly one of the tests I want to try. A tail resistor has one big advantage: It's impedance is uniform with frequency.

[nigel pearson]

Originally Posted by tvrgeek

Exactly one of the tests I want to try. A tail resistor has one big advantage: It's impedance is uniform with frequency.

I feel with a clean supply it works very well . My beloved Hitachi design has a 47 K tail resistor . 7 active devices which could be reduced to 5 if the double VAS was made single VAS and bootstrap CCS if so . Some will tell you bootstraps need nearly 100 % positive feedback to work . 70 % still is usable . 97% as in complimentary feedback pair is a bit high and sometimes needs a series resistor . 94 % is ideal .

The Hitachi I sometimes build is 8 devices + 3 diodes as I use a tail CCS .