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In Reply to: Re: The Sound of AD1851 vs. TDA1541. Silicon chromium resistors and other things posted by Elso Kwak on April 22, 2001 at 04:51:09:
Hi,I have two DACs with TDA IC's, both without dig. filter and using CS 8412 as DIR. Few days ago there was listening session where some comparations between those two were made. Here are the results: 1541 DAC has better resolution but 1543 was also good. 1541 is smooth and warm with beautifull timbre. In comparation, 1543 is a bit agressive and grainy, but still better than commercial DAC with double BB1716 (balanced) with discrete analog stage and upsampling unit (with CS8420).
My 1541 DAC is also much more expensive to made than 1543. It uses shunt regulated stabilizers for every PS pin (with pre-regulation and heavy filtration), Siemens Sikorel and Sanyo OsCon elecrolytic caps, Wima film & foil caps on 1541, Mundorf Supreme coupling caps and holco resistors. IV is passive with 82R holco resistor. Analog stage is simple current sourced anode amplifier made with one Sovtek 6922 tube. Innitially I had hexfet source follower after tube but it sounds better (cleaner) without it. I also found that decreasing IV resistor value "kills" dynamics, what goes against advices I read from others (or is this true just for BB PCM63?), so I'm going to try even higher values. I'm also intending to try transformer (perhaps Lundahl) for DAC-tube coupling. Anyway, as it is, this DAC is far better then commercial units I listened to.
But, for those on a budget 1543 is wonderfull solution- cheap and no need for extra analog stage. My design is based on a Kusunoki DAC but with a few modifications. First and most important is that this DAC sound much better with 3 1543's instead of 4 when the bias resistor is changed to 432R and load resistors to 470-560R. This change even has influence on THD. With original (330 & 680R) resistor arrangment and 4 IC's DAC has THD of ca. 0.2% and new DAC has ca. 0.05%. Perhaps it is interesting that 0.05% THD comprising of 2. 3. and 5. harmonics sounds better then same value THD comprising of just 2. and 5. harmonic.
However... TDA 1543 is also very good and perhaps excellent solution for bellow high-end systems.Best regards,
Vuki
Follow Ups:
I believe that Audionote uses a 300 ohm I-V resistor. Of course the AD1865 puts out less current than the 1541 so a larger resistor will give you more voltage, but at what distortion? It makes sense to me that too low of resistor value would squash dynamics, too large a value would give too much distortion. That is what makes this all interesting. We get to experiment to find out. And we use our best intrument in determining the best way (our ears!).
Enjoy.
Ric
Hi Ric,why do you think a low value for an IV resistor would squash dynamics? Current sources want to see as low an impedance as possible. The playing around I've done tends to confirm this, although you then have the problem of gatting decent gain from an amp / transformer. I'm interested in your thinking.
Also I understand that you tried a few different options for your latest DAC. Can you tell us what conclusions you came to, if it's not too top secret? Just interested in talking hifi. ;o)
Daniel Espley
Hi Daniel,Low value I/V resistor really doesn't sound good, at least on 1541. I tried it (20R) and it sounds "dead" compared to higher value (82R currently and I'll try higher).
Now, if you are planning to use step up transformer and tube output, low resistor could sound better because higher value I/V R could overload tube (and transformer). I think that I/V interstage transformer should be 1:1 to 1:3 max. I'm going to try that soon.Best regards,
Vuki
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