Replace PCM63 by PCM1704 DAC chip - diyAudio
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Old 28th August 2006, 03:29 AM   #1
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Default Replace PCM63 by PCM1704 DAC chip

I have the tube DAC from Tentlab with a PCM63K DAC chip. I use a 6021W pencil tube in the analog output stage. (cathode resistor is changed to 150 Ohm bypassed with a Black Gate 470 µF elco.)

http://members.chello.nl/~m.heijlige...tml/dactop.htm

After reading about a PCM63-PCM1704 adaptor from Monarchy Audio I wish to replace the PCM63K by the adaptor with a PCM1704K ($90.00 for two adaptors).

The Piggyback Killer PCM63 Adaptor

The following questions arise:

Because I have the SM5847 dropin replacement for the SM5842 from Tentlabs it must be possible to set the data length to 24 bit output for the PCM1704.

This DAC uses 16 bit from the CS8412 to the digital filter.Is it possible to set this higher and is this better for the sound?

In this forum, I learned that the switching for the PCM63 and the PCM1702 is not identical (the PCM1704 is identical with the PCM1702?). Because this DAC reclocks each signal I don't think this is an issue?

Now the big question : Results this in a better sound?
I know that only 44,1k is possible with the builtin VCO.
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Old 28th August 2006, 03:38 AM   #2
singa is offline singa  Singapore
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Cs8412 does not process 24 bit.That's why 8414 came into picture but smt need adapter and finally 8416 has replaced 8414.
Better sound?You are the experimenter please tell us how it is.
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Old 28th August 2006, 03:54 AM   #3
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Quote:
finally 8416 has replaced 8414.

Is there already a CS8416 to 8412 adaptor available?
Kind regards.
JP
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Old 28th August 2006, 04:00 AM   #4
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Quote:
Originally posted by singa
Cs8412 does not process 24 bit.
It will pass 24 bits. Even the ancient SAA7274 can do that. The CS8412 is simply not rated to 96k.Otherwise it is no different to the CS8414.
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Old 28th August 2006, 10:37 AM   #5
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Check these people, they have several adapters available:

http://www.audiotuning.de/

No cheap though...


rgds,

- dan
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Old 29th August 2006, 05:22 AM   #6
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Quote:
Check these people, they have several adapters available:
Thanks. Nice but expensive.
JP
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Old 29th August 2006, 05:40 AM   #7
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I replaced the PCM 63 in the Tentlab DAC with PCM1702.
They were placed on two little adapter boards from LINN Numerik I think.
The results were:

output signal was lower (less Iout)
A little bit brighter sound but practical identical.

I compared the DAC against a old QUAD 66 with LC clock modified.

Both sounds good. The DAC was more transparant with a broader image and better placement of the instruments but not a difference of day and night.

Is it really worth to replace an older DAC chip with a state of the art (PCM1704) newer chip?

Is it true that most DAC chips sound alike?

JP
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Old 29th August 2006, 07:11 AM   #8
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Quote:
Originally posted by jpfastre

Is it true that most DAC chips sound alike?

JP
A DAC designer, the boss from Hoerwege - Stefan Horwege (www.hoer-wege.de) told me once that in a complete set of a converter, the sound is defined about 30% by the converter chip, 30 % goes to the output stage and 30 % by the quality of the power supply. The remaining 10 % are the choice of filter, receiver and PCB layout etc.

Changing the PCM1702 to the PCM1704 (an idea that I was thinking about, since my player has them too) would bring you thus only a small change / improvement.
Bu there is a significant sound difference, when you choose between a R2R (multibit) chip or a bitstream (1 bit) type, they fundamentally have a different sound, and here is where your taste matters.
Personally I don't like the 1 bit sound too much, and if you surf thru the forum, most people prefer multi bit types.

Rgds,
- dan
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Old 2nd September 2006, 06:29 AM   #9
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Quote:
the sound is defined about 30% by the converter chip, 30 % goes to the output stage and 30 % by the quality of the power supply
Stefan Horwege is probably right with his statement.


Quote:
After reading about a PCM63-PCM1704 adaptor from Monarchy Audio I wish to replace the PCM63K by the adaptor with a PCM1704K ($90.00 for two adaptors).

Now there is also a PCM63 to PCM1704J adapter available from Tentlabs. Price and results are not yet available.
I look for more information for the results with the tubedac from Tentlabs.
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Old 2nd September 2006, 01:26 PM   #10
A 8 is offline A 8  Sweden
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Some consider the PCM63 one of the better sounding dac chips.

Make a search and you'll see.

I've had both and there is a difference but if you only running 16 bits then I would not go throgh the hassle of changing.
In short I found the 1704 to present a bit more detail and may not be as "warm" sounding as the 63 which depending on the rest of your stuff might be good or bad.
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