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Old 11th March 2003, 10:47 PM   #11
casouza is offline casouza  Brazil
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"I am not an expert but as you indicate I've read that the logic for parallel dacs is the they will average linearity errors but on the other hand is that not what a balancen configuration will do as well? "

Correct, the paralel DACs will average LSB errors and will help randomize quantization noise. The overal effect is less distortion and probably a better signal to noise ratio. This tweak is performed by soldering one DAC on top of the existing one.
If you want to do it, better strive for the average of two excellent Dacs, for example BOW uses the selected, more linear PCM 1702- K suffix. I see no point in paralelling non-select DACs, it may even sound worse.

I have no direct experience comparing the two topologies, however, I hear a brighter sound on the few differential DACs that I have auditioned.
Again, it's a matter of taste, some people may prefer a more incisive presentation, I prefer a more mellow, acoustical presentation (NOT undynamic).
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Old 12th March 2003, 08:53 AM   #12
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You can only parallell current output DAC's without problems. Voltage output units need to share load through resistors which is not optimal.

Parallel DAC's will have many advantages such as dynamic range, noise, lower bit distortion, output impedance etc.

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Old 12th March 2003, 01:29 PM   #13
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Quote:
Originally posted by Petter
Parallel DAC's will have many advantages such as dynamic range, noise, lower bit distortion, output impedance etc.
OK, maybe but high much really? Take the PCM1792 for instance. Isn't this chip rather good as it is?
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Old 12th March 2003, 01:44 PM   #14
casouza is offline casouza  Brazil
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Thumbs up Parallel DACs

If you mean the PCM 1702 DAC, BOW technologies advertises that the latest version with parallel chips sounds much better than the early version with one chip per channel.
I borrowed a BOW ZZ Eight from a friend for a week, I was in heaven!
Unfortunately it is too expensive.
I hope this helps
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Old 12th March 2003, 01:50 PM   #15
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Default Re: Parallel DACs

Quote:
Originally posted by casouza
If you mean the PCM 1702 DAC
No, the state of art PCM1792, 132 dB S/N. Datasheets aren't availible yet.

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Old 12th March 2003, 05:09 PM   #16
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One should expect n times dynamic range for parallell operation.
Random noise should theoretically go down by sqrt(n)
Noise should also be possible to reduce given that one needs lower value resistors to obtain the same IV characteristics

If one were to shift the units by say a few clock cycles one would also get a filtering effect which would be cool. I have looked at this extensively and it is relatively easy to do.

With parallell units one might also be able to get by without buffer stage which saves at least one amplification stage with it's inherent distortion.

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Old 12th March 2003, 05:41 PM   #17
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Connecting DACs in parallel will only improve the dynamic range if the noise limiting the dynamic range is uncorrelated between the two DACs. If the DACs are quantization noise limited, then no improvement would be expected because the quantization noise between the two DACs is completely correlated.

Shifting the input to the second DAC does indeed produce a filtering effect similar to a rectangular FIR filter with two taps. This would tend to reduce quantization noise at higher frequencies, but it will also filter the signal.

Possibly two oversampled (noise-shaping) DACs would benefit from being paralleled if their reset times are staggered. Staggered reset would to a certain extent break the correlation between the quantization noise in the two DACs.
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Old 12th March 2003, 05:53 PM   #18
casouza is offline casouza  Brazil
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Smile New chip on the block

Sorry, I thought it was a typo.
best wishes
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Old 12th March 2003, 07:59 PM   #19
grataku is offline grataku  United States
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Petter,
"Hmmmm"....how does paralleling dacs increase dynamic range?
Maybe I have a misconception of what dynamic range is...I think of dynamic range as 1 part in 64k for 16 bits digital signal coming from the CD.


Mikewu99,
random noise + random noise= more noise or less noise?
I think it equals less noise only in the presence of coherent signal which is what we would have here. Yes?
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Old 12th March 2003, 08:24 PM   #20
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Well my DAC started of with 1 TDA1541 then 2 x TDA1541 and then 2 x TDA1541s1.

The way i've done it, is a by having 2 seperate identical dac prints which get the same input.

In my setup there is a big difference between a singel dac and 2 dacs parallel, there is way more details and control with 2 dacs.

Some day when I get the time, I plan to build 2 dac prints more to see if the gain is just as big as from 1 to 2 dacs.

I also considered balanced, but droped the idea because it's way more differcult than non balanced and also because non of my other gear is balanced.
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