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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 KHz

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Kastor L

Kastor L

Member
Joined 2014
kiriel.se
Soekris wrote LME49724 earlier, I think rredline was asking about LME49990 instead of LME49724, since LME49990 has lower THD and IMD specs.

If this is pure Current out, then there should be no LME49724.

A quite large percent of this forum believes resistors sound different, so if they are Carbon, metal-film, Tantalum, Silver and so on is a tech consideration IMHO.
 
H

HpW

Member
Joined 2002
hpw-works.com
Kastor L said:
A quite large percent of this forum believes resistors sound different, so if they are Carbon, metal-film, Tantalum, Silver and so on is a tech consideration IMHO.
Click to expand...

IMHO, it's a metallurgical question (metal to metal voltage & current), how the connections to the internal substrate and whether you have a inductive free internal design & trimming; followed the soldering of the resistors to your PCB.

It may be optimal to have all resistors in one ceramic substrate & laser trimmed.

Finally the RF question rises, while the Analog is not fully isolated against the digital... while a RF wave signal does not stop on the end, it will emit... source & sink dependent. Not only internally also it will flow source & sink dependent over connection wires to other equipments.

This is not an easy task to solve analog & digital shielding .. just my experiences using electric & magnetic near field probes :eek:

Just my 2 cents

Hp
 
andrea_mori

andrea_mori

Banned
Joined 2005
reodds said:
The design is really not up to discussion. Søren is obviously an excellent engineer, knows exactly what he is doing, and needs no further input from anyone.
Roger
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Since the thread has moved into the Vendor's Bazar section, everyone is free to buy or not this DAC as is, the Vendor made the design choices....

... but, I find just curious that everyone can discuss Scott's design
http://www.diyaudio.com/forums/solid-state/156474-yet-another-discrete-op-amp.html (also John's and Nelson's design), while noone can do the same about Soekris's project....

Maybe, I'm living in the World 1.0 too ....

Andrea
 
E

esgigt

Member
Joined 2013
CZ101 said:
What a waste of time! (not to mention $)
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agree 100%

I hope Kastor L has already checked the price of 0.01% resistors and the availability in the several types... I guess he'll need a (sub-prime) mortgage :D

EDIT: available types (0.01%) are only various metal film types. Prices (piece) range from €7,42 (@ 50+ pcs) to €36,45 (@ 50+ pcs) ... LOL ... prices, sales tax excluded
 
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S

soekris

Member
Joined 2009
soekris.dk
Paid Member
CFT said:
So Søren we should hear from you how your dacs will sound like in a couple of weeks? What dacs would you benchmark yours with? Thanks!
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I should have music though it in a couple of weeks, my references are not that fancy, an older Sony ES series CD player and a Cambridge DacMagic Plus, plus a Sennheiser HD-650. But don't expect me to be objective :)

rredline said:
BTW, is there any consideration to use LME49990 on the buffer stage? Some say it is a better choice.
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Since the opamps are not really stressed, unlike most DAC I-V circuits, I feel the used parts are perfect for the needs, although I also have considered a LME49990 on the highest grade version.

But I do also like building discrete circuits, so later on a version with fully discrete output amplifiers might come out.... See a couple of my older post that never got anywhere:

http://www.diyaudio.com/forums/soli...er-mosfets-2sk3497-2sj618-little-testing.html
http://www.diyaudio.com/forums/soli...-amplifier-non-feedback-production-ready.html
http://www.diyaudio.com/forums/solid-state/156674-my-take-buildable-discrete-op-amp.html

reodds said:
+1 Jean-Paul, you have distilled what should have been said right after post #1. The design is really not up to discussion. Søren is obviously an excellent engineer, knows exactly what he is doing, and needs no further input from anyone.

Roger
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Actually I would love competent input on the digital filters, seems to be plenty opinions around whats best, from no oversampling/filters, to very long FIR filters, or to FIR filters. Preferable supported by objective test or papers....

beardman said:
When the direct output is used (not the opamp output )..shall we use a caps on this direct out ??
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The direct resistor string output has zero DC offset, filtering only per personal preference...

esgigt said:
EDIT: available types (0.01%) are only various metal film types. Prices (piece) range from €7,42 (@ 50+ pcs) to €36,45 (@ 50+ pcs) ... LOL ... prices, sales tax excluded
Click to expand...

Thankfully I'm not buying resistors the same place as you :)
 
G

Greg Stewart

Member
Joined 2003
Paid Member
soekris said:
<SNIP>
Actually I would love competent input on the digital filters, seems to be plenty opinions around whats best, from no oversampling/filters, to very long FIR filters, or to FIR filters. Preferable supported by objective test or papers....
<SNIP>
Click to expand...

Check out John Swenson's thoughts:

Upsampling Impressions

and in this thread:

Are we just kidding ourselves? - Page 5

And an observer's thoughts on the results:

http://bottlehead.com/smf/index.php/topic,4086.msg54324.html#msg54324

Greg in Mississippi
 
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