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Old 5th April 2012, 08:46 PM   #1
anli is offline anli  Russian Federation
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Default NFB-free discrete IU

...for +/- 2 mA input: schematics and "harmonics' SPL". I have designed it to be used (and it is in use) with PCM63.
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Last edited by anli; 5th April 2012 at 09:51 PM.
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Old 5th April 2012, 09:07 PM   #2
jcx is online now jcx  United States
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sorry but EF are 100% negative feedback circuits - check EE textbooks instead of Audiophile rags ad copy
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Old 5th April 2012, 09:16 PM   #3
anli is offline anli  Russian Federation
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Quote:
Originally Posted by jcx View Post
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?
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Old 5th April 2012, 09:27 PM   #4
jcx is online now jcx  United States
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"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
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Old 5th April 2012, 09:52 PM   #5
anli is offline anli  Russian Federation
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Unsubscribing..
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Old 7th April 2012, 12:39 AM   #6
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Quote:
Originally Posted by anli View Post
...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.
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Old 7th April 2012, 08:43 AM   #7
tinitus is offline tinitus  Europe
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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


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Old 7th April 2012, 09:45 AM   #8
anli is offline anli  Russian Federation
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Quote:
Originally Posted by Trevor White View Post
what is the input impedance of this circuit ?
Few Ohms - depending on used Q4.

Quote:
Originally Posted by Trevor White View Post
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).

Quote:
Originally Posted by Trevor White View Post
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.

Last edited by anli; 7th April 2012 at 09:48 AM.
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Old 8th April 2012, 09:41 PM   #9
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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
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Old 8th April 2012, 10:03 PM   #10
anli is offline anli  Russian Federation
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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.
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