Service manual for D-1 DAC

LBHajdu

Member
2002-02-18 7:53 pm
Nelson Pass has just recently published the Service manual for D-1 DAC

Nelson Had written this at the top of the manual : “This is not intended as a project and will not be supported as such. DO NOT CALL US.”

The link is : http://www.passlabs.com/pdf/d1-srv-man.pdf

Let me be the first to throw out a question. The I\v stage of this DAC can be applied to almost any DAC the only requirement being that the DAC chip have + and - polarity signals coming out of it. The PCM63 only has one phase, so two PCM63's have to be used, one for each phase. This means that the digital information going to negative DAC has to somehow be “?reversed?” I’m not really shore how this is done. If the 83C750 microcontroller is involved in doing this it will be hard for diy enthusiasts to follow. Does anyone know how this is done ? Diyers could may have to build half of the I\v and run it single ended.
 

mozfet

Member
2002-03-18 4:23 pm
If you have to ask the question I would recommend you do not attempt this project, there are simpler DAC projects that are still very interesting, the Kusonoki (prob incorrect spelling!) being one. I'm not trying to put you down here, but I doubt there is anything more frustrating than having expended considerable effort and being left with a non-working project. Try the Kusonoki with the CS8412 and TDA1543, you really cant do much wrong with it.

Mozfet:cool:
 
Phase Reversal for Balanced DAC's

Hi All.
Yes the phase reversal is accomplished by the 74HC86 by inverting the data. This works well for two's complement data except for the least significant bit. It could also be done with a 74HC(U)04 or by taking the Q Bar output of the Data of my asynchronous reclocker (MC74VHC74)
I know Philips is using a 74HC04 in one of there CDP's. If I recall right it was a CD850.;)
The DAC feeded with inverted data has the inverted audio output. I am using it in my KWAK-DAC.;)
 

LBHajdu

Member
2002-02-18 7:53 pm
I have looked up the truth table for the EXCLUSIVE-OR GATE and constructed a table for this system(see pic below). It does indeed appeared that the SN54HC86 is taking all the data and just inverting it before it reaches the Data pin of the lower DAC( - ). I can only conclued that the reason this was done instead of just using a not gate was to keep the timing on all 3 pins synchronized.
 

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LBHajdu said:
The I\v stage of this DAC can be applied to almost any DAC the only requirement being that the DAC chip have + and - polarity signals coming out of it. The PCM63 only has one phase, so two PCM63's have to be used, one for each phase. This means that the digital information going to negative DAC has to somehow be “?reversed?”

Diyers could may have to build half of the I\v and run it single ended.

The I/V stage will work with single ended signal as well. You just use half of the circuit and modify the volume control (as you stated later).