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Old 13th May 2004, 09:50 PM   #1
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Default Separate DACs for each halfwave ?

Hi,

is there a DIY project with separate DACs for each halfwave ?

My Technics SL-P770 got that IMHO.

2 x PCM56 per channel, each fed from a different data line...

Noise floor & distortions with -60dB signal are about 6 dB better compared to any of my Philips players.

Also it claims to be a 18bit DAC while PCM56 is 16bit.

2 bits won from splitting ?

Any chance to get schematic of this player ?


Bernhard
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Old 13th May 2004, 09:58 PM   #2
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what about midscale error? PCM56 says:

Quote:
Initial Bipolar Zero Error (Bit 1 “on” and all other bits “off”)
is the deviation from 0V out and is factory-trimmed to
typically ±30mV at +25°C.

so we take one DAC with worst case +30mV at midscale, and one with -30mV at midscale. This amount of crossover distortion has the big advantage we can go class c in the power amp without doing significant more degrading the THD.

You are sure the 2 DACs ar not in balanced or parallel confiduration?
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Old 13th May 2004, 10:14 PM   #3
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4 different data lines coming from a Technics >40pin smd ic.

Outperforms 1541 S1, 6 dB better distortion & noise.
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Old 13th May 2004, 11:56 PM   #4
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Quote:
Originally posted by Bernhard
4 different data lines coming from a Technics >40pin smd ic.

Outperforms 1541 S1, 6 dB better distortion & noise.
Very typical of you, Bernhard.
Don't take me wrong but LISTEN to the TDA1541 S1.
Whatever it measures, the TDA1541 (in all its versions) gives the best sound I've heard coming from a CD IMHO.
Put a good clock on both players, a good analog stage and compare.
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Old 14th May 2004, 03:53 AM   #5
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sorry carlos, but your post is absolutely of topic.
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Old 14th May 2004, 04:15 AM   #6
azira is offline azira  United States
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Just working through this. Minimum FSV for the PCM56 is +5 volts. Say you level shift one of them from -5 to 0 and the other sits from 0 to 5. With a bipolar output stage to recombine the outputs, you could get effectively 17-bit @ +10 volt resolution. It's not 32 bits resolution. MSB voltage value = 5 volts + 16 bits resolution left to resolve 5 volts... right back where you started.
I don't think you would gain any higher resolution from this topology unless you fix the output voltage requirements for each scenario.
In addition, unless you're creating an A/D -> D/A processing pair, you'll have to find a way to drive a 32-bit signal digital signal.
--
Danny
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Old 14th May 2004, 06:10 AM   #7
Pedja is offline Pedja  Serbia
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Bernhard, 1541 is technically enormously obsolete part and if you are in search for good distortion specs do not waste your time with it. Almost any recent unit is better. Did you know, there are even chips like this (see below)? And you can have that for the price of ‘41/S1.

Pedja
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Old 14th May 2004, 06:17 AM   #8
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Quote:
Originally posted by Pedja
Bernhard, 1541 is technically enormously obsolete part and if you are in search for good distortion specs do not waste your time with it. Almost any recent unit is better. Did you know, there are even chips like this (see below)? And you can have that for the price of ‘41/S1.

Pedja
Pedja,

which one is this ? Multobit ?
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Old 14th May 2004, 10:09 AM   #9
Bricolo is offline Bricolo  France
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BB PCM1794, I think
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Old 14th May 2004, 01:29 PM   #10
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Quote:
Originally posted by till
sorry carlos, but your post is absolutely of topic.

Just want to say that a well implemented NOS TDA1543 sounds to me much better than a PCM1738.
Delta-Sigma?
Bistream?


But the 1543 will measure much worst than "modern" Dacs.

Ok, sorry for this.
Keep measuring!
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