NFB-free discrete IU

[anli]

...for +/- 2 mA input: schematics and "harmonics' SPL". I have designed it to be used (and it is in use) with PCM63.

 

[jcx]

sorry but EF are 100% negative feedback circuits - check EE textbooks instead of Audiophile rags ad copy

 

[anli]

sorry but EF are 100% negative feedback circuits - check EE textbooks instead of Audiophile rags ad copy

Thanks for your so deep schematics analysis!

Please, stop terminology war here, OK? And, please, stop speculations about forum members' reading - you don't know me, my education, my reading and so on. Just stop. And be kind. Aha?

 

[jcx]

"no negative feedback" is a Audiophile marketing construct - doesn't help diy memebers learn how to design, evaluate circuits

few useful electronic circuits can be designed without negative feedback - in your circuit's case there are multiple local negative feedback subcircuits

don't title threads with such loaded terms and you won't have "terminology war" "problems" I wouldn't bother if you accurately used "no Global negative feedback" in the title

 

[anli]

Unsubscribing..

 

[Trevor White]

...for +/- 2 mA input: schematics and "harmonics' SPL". I have designed it to be used (and it is in use) with PCM63.

what is the input impedance of this circuit ?

For an IV converter it needs to be very low but I don't think it is much better than one grounded base circuit.

 

[tinitus]

whats up guys ?

why do you behave like this, just because of a 'simple' schematic ?

if you have no interest, just walk away

personal posts removed


moderation

 

[anli]

what is the input impedance of this circuit ?

Few Ohms - depending on used Q4.

For an IV converter it needs to be very low

Any schematics is a result of compromises in designer's model of the world (and, in audio, it depends on experience of multi-years music listening and correlation between used schematics topology and subjective opinion) To my taste input impedance is sufficient for the case (DAC output impedance about 670 Ohms - it is simulated with Rdac).

I don't think it is much better than one grounded base circuit.

It is common base - Q2 just fixes input voltage about zero in thermo-independent way.

 

[Torchwood421]

Hi anli, How does it sound? I'd be interested in using it with a TDA1541A. Have you tried an AD844 based I/V? Thanks for any comments... Dave

 

[anli]

Before current one I have used an IU as attached (the schematics isn't my, as a result - fragment only). To my taste, current IU is distinctly better (the difference isn't subtle): "Cu is Cu rather Al" - you see? While technologically it is easy to replace an IU (it is separated from main DAC board), during almost two yeas I haven't any intentions to design something better (but, say new amplifier has appeared ). Mostly I listen to live records (mainstream 50-60 jazz and different classical music).

You see, it is just subjective opinion.

 

[Torchwood421]

Hi anli, Thank you for your thoughts. Yes, I agree it is always a subjective opinion. I am using a Pedja AD844 IU, so in this case we have a similar reference point. I am listening to modern blues these days and some rock. Thank you, Dave

 

[anli]

R2, R4+Q3, R9 and R12 are for taking part of dissipating power form appropriate active elements. Q3 (as well as many other schematics elements) is also for increasing of input elements output impedance for better PSRR.

 

[Tazzz]

...for +/- 2 mA input: schematics and "harmonics' SPL". I have designed it to be used (and it is in use) with PCM63.

Why the addition of Q3 and R4 seems Q4 would see a low impedance from Q7 without them.

And also how do you handle dc offset I do not se any servo.

 

[anli]

About servo. To my taste both IU and amplifier must be true DC (while any servo is HPF). This opinion is a result of multi-year true DC audio-chain using. The schematics is balanced except for output follower. As a result, thermal drift is slightly above 2 mV/C, or less than 0.1%/C - it is useful to present in percents to avoid drift-phobia

 

[regal]

sorry but EF are 100% negative feedback circuits - check EE textbooks instead of Audiophile rags ad copy

Feedback is needed in a SS discrete UI, at least if you want less distortion than a simple passive I/v + tube. Its a hard pill to swallow for some but I have never seen a NFB free bjt UI that has less than ~-80db 2H, bjt's aren't linear enough without nfb.

 

[anli]

Feedback is needed in a SS discrete UI, at least if you want less distortion than a simple passive I/v + tube. Its a hard pill to swallow for some but I have never seen a NFB free bjt UI that has less than ~-80db 2H, bjt's aren't linear enough without nfb.

(marked as bold by me) He-he... There aren't (and, I guess, will not appear already) trustworthy psychoacoustic tests proving any correlation between this understanding of "linearity" and "our ears understanding of linearity" (or, if we a saying about our ears, of naturalness).