Rec. output stage mods- Sony DAS-702es NOS dac

homemade

Member
2004-07-22 3:42 am
us
Just acquired a most interesting Sony DAS-702es d/a converter. 30+lbs. Extreme build quailtiy. ELNA Cerefine/ film capacitors throughout. The dac chips(2) are #cx20017. From the info I have gathered , these are 16 bit, voltage out , with NO oversampling , NO digital filter. Just a LPF with 3 TI 5532 opamps per side. The amazing thing is how GOOD this thing sounds. It bests my Scott Nixon (1543)and Paradise(1545) battery powered dacs in detail and bass. It is also more extended(but not bright!). Just as a reference , I'm using gainclone amps with my open baffle speakers , with ESG-1 ribbons on top. Linkwitz OB subs below 150hz. My transport is an NEC cd-rom drive(several types). I remember all the talk years ago that the first gen of players had a 'glare' to them , but certainly not here. Very enlightening. Anyhow , to my request. Can anyone tell me if I can take the signal directly from the dac chips? Or should I use other opamps(which do you rec.) . I would prefer to do this without to much surgery. All help is much appreciated.
 

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tubert

Member
2009-04-09 11:58 pm
Q1. Can anyone tell me if I can take the signal directly from the dac chips? Or should I use other opamps(which do you rec.) . I would prefer to do this without to much surgery. All help is much appreciated.

A1. I think not. It looks to me like this dac sends 16 individual voltages to the sample/hold circuitry and even if it doesn't, taking a 'tap' from the dac would require a massive overhaul of the main circuit board.

The reason this unit sounds so good is in fact, because of the build quality, not the technology it uses.

Q2. Sorry to bump such an old thread but I've just bought one of these myself and am keen to know what the blue switch banks do (see post 2 for pic). Does anyone know?

Flicking them does alter the sound but I don't know what each individual one does.

A2. These switches contol the gain of each chanel. It's just a resistor network with different values for each "flick".

Why did a noob join this board? I've had one of these units since 1990 and 6 months ago one chanel went bonkers. It just started making the worse noise I've ever heard and it's obviously not an analog issue. You can still buy the serial data converter but I suspect the dac and as you can see from the pics above, you can't read the part number.

So now I'm off to find a SONY CX20017 dac. Thanks for the info on the chip and I hope my advise helps you guys.

}---:)
 
Sorry my replying to this 10 years old thread. I recently got Sony DAS-703ES and tried some mods. I think 703 is quite equivalent to 702 circuit-wise.
Hope my trial to be some help for someone so that this old school Sony lives longer. Actually, I was working for Sony 20 years ago, not directly for consumer hifi, though.

Firstly, DAC chip of 702 seems to be PCM53, current out ver., from web sources, very similar to 703’s PCM53JP-I. And the metal can op amp with heat sink, LF356, works as IV.
My complaint to the sound of stock 703ES was it is too much veiled and masked, even worse than CDP-101 in this aspect.

My mods are as below, in priority order.
1) Escape from tons of 5532 in LPF stage
Replacing 5532s with AD827s works. Good less surgery option.
Or, bypassing all of 5532 related circuit by using 10mH inductor. Recommended.
2) Bypassing M5240 in output stage
Since this unit already has FET buffer before output push pull stage, we can simply remove M5240 and short +IN and OUTPUT of M5240 location.
With this, we need to accept worse THD+N, maybe around 0.2%, but I believe no one here cares.
3) Replace LF356 with your favorite op amp
Stock LF356 is nothing bad. In my case, though, I put AD797 for more detailed resolution.

You can find some pics and more details in below site.
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