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Old 10th February 2013, 02:20 AM   #191
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Couple of days ago we compared my Cary 303/200 using just the I/V of the AD844, up against the Thorsten Losetch designed AMR CD77 (TDA1541 double crown) that uses Thorsten's special designed I/V stage which I believe is tube based, output impedance <100ohms, so a good match with the Lightspeed as is the Cary. I was expecting the AMR to be better, just by it's reputation and the designer behind it.
3 of us within 20sec thought the Cary was a clear winner, top to bottom, front to back and side to side, and it remained that way for the rest of the session, the owner of the AMR was mute and stone faced and said nothing for the 1.5hrs of A/Bing, and probably saddened by the result, the listening session which went for 4hrs, the last 2.5hrs was the Cary only.
The system was my Lightspeed Attenuator feeding 2 x Halcro DM-78 monoblocks (input impedance 100kohms) pushing a pair of Wilson Watt puppy 8's

This proved what I've been hearing that this AD844 as an I/V is something very very special when used as I've done with no feedback.

Cheers George
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Old 10th February 2013, 09:14 AM   #192
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So let's get this clear George you're saying PCM1704 with your AD844 beat out Thorsten's TDA1541A with tube stage? If so, I'm perplexed by such a result.
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Old 10th February 2013, 09:18 AM   #193
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Why so? 844 + 1704 is a good match. 1704 + PMD200 - another good match.
Not to mention both 1704 and PMD200 are in the 5 best DACs/DFs ever made category.

Tubes in I/V is a matter of taste...
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Old 10th February 2013, 09:20 AM   #194
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Well mainly because the TDA1541A is clearly a better DAC technically than the PCM1704 - much lower glitch by virtue of being segmented current source architecture rather than R2R.
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Old 10th February 2013, 09:26 AM   #195
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Default what to do with 6ma dac output

hallo ,

any idea ?

my dac gives 6 ma peak output ,to use Ad844 i propose 47 ohm parralled with AD844 input (no feedback).
that means AB844 gets 3 ma.


is that OK or do you have other solutions???
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Old 10th February 2013, 09:36 AM   #196
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Quote:
Originally Posted by abraxalito View Post
So let's get this clear George you're saying PCM1704 with your AD844 beat out Thorsten's TDA1541A with tube stage? If so, I'm perplexed by such a result.
Yes I know, I was sure the AMR should have been the better, given it's hype. And I'm not pulling any ones leg here either.
The Cary had far better dynamic swing, far more detail, clearer lower punchier more defined bottom end, more extended transparent high end, a mid range that had more body to it.
We just wanted to keep turning up the volume on the Cary because it never gave any sense getting confused, it's like there was more air around the notes to let you hear what was going on with a blacker back ground. It made the AMR sound like a good old tube amp of yester-year, you know a bit slow a bit thick yet musical still.

Cheers George
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Old 10th February 2013, 09:45 AM   #197
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Quote:
Originally Posted by abraxalito View Post
Well mainly because the TDA1541A is clearly a better DAC technically than the PCM1704 - much lower glitch by virtue of being segmented current source architecture rather than R2R.
upper 3bits of older ,conventional (not sign magnitude) DAC such as PCM58 or PCM56 etc. were segmented current source .
I think each upper bits of PCM1704's two 23bit DAC have same architecture.
hence their major glitch would be same level.
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Old 10th February 2013, 09:53 AM   #198
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PCM1704, 63, AD1862 et cetera are in the same league, more or less.
1541 has a bit cleaner switching in theory, yet it has it's flaws in real life - limited oversampling frequency, 16bits and single-chip with common supplies for both channels...

Most of the performance comes from IC's surrounding and their tradeofs management.
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Old 10th February 2013, 11:03 PM   #199
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Originally Posted by vandenberg View Post
hallo ,

any idea ?

my dac gives 6 ma peak output ,to use Ad844 i propose 47 ohm parralled with AD844 input (no feedback).
that means AB844 gets 3 ma.


is that OK or do you have other solutions???
That is much more that the PCM1704 so I would just try from the TZ (pin 5) a 1.5k and 1000pf to ground as Pedja did with the TDA1541. And also try the output buffer as is, or something better by comming off the TZ pin to it.

Cheers George
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Old 11th February 2013, 01:17 AM   #200
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Quote:
Originally Posted by georgehifi View Post
Yes I know, I was sure the AMR should have been the better, given it's hype. And I'm not pulling any ones leg here either.
The Cary had far better dynamic swing, far more detail, clearer lower punchier more defined bottom end, more extended transparent high end, a mid range that had more body to it.
I have an idea that perhaps its incompatibility between the Halcros and the AMR. Halcro from what I know of it is an ultra-low distortion, ultra high-feedback design. The AMR being normal NOS puts out lots of out-of-band images between 22 - 44kHz. Perhaps this ultrasonic output upsets the Halcro and saps the dynamics.
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