Sony DAS-703ES DAC is in the house!

mhedges

Super Member
So I just took delivery of a Sony DAS-703ES DAC, thanks to a fellow AK'er who answered my wanted ad. This is a very rare piece. It was the first consumer DAC sold in the US. Retail was $1800 in 1986.

There isn't alot of info available on it but it seems to be well thought of. It was a no-corners-cut piece, and a lot of the stuff in it went into the DAS-R1. Some sources say that it even exceeded the DAS-R1 in terms of spare-no-expense detail.

It uses the Burr-Brown PCM53JP DAC, which doesn't quite have the cult following of the TDA 1541 S1 but is still considered one of the best early DACs.

Build quality is phenomenal. As you may know I am no stranger to Sony ES gear from its golden era and this outstrips them all. It has a rock solid feel, all exterior panels are milled aluminum, even the lid.

Inside it is the cleanest piece I have ever seen. The cover lid sealed in a near-hermetic fashion. There is no trace of dust anywhere, and the copper "lunchbox" that shields the Digital section has a beautiful luster without a hint of tarnish. It looks like it was built yesterday.

All electrolytics are Elna Cerafine, and are very high voltage for a line-level component. Main smoothing caps are 71V 2200uF (x4) and the analog board caps are 330uF 100V!

Cosmetic condition is near mint, with just a few dings on the edges. The glass window on the front looks great.

Interestingly it looks a little different inside than I expected. It only has one transformer- all the pictures I have seen have two transformers. The main coupling caps are yellow cylindrical film caps, not the rectangular caps seen in other pictures (although actually there appears to be a lot of variety to those caps, judging by the pics). The board is clearly designed for a large film cap in this spot and I'm going to have trouble resisting the temptation to replace them with Mundorf MKPs or similar.

How does it sound? No idea - haven't hooked it up yet :). I probably won't untill the Christmas tree goes, as it is hard to get to the stereo with the tree where it is. It powers up and I was told it is in perfect working order.

Anyway enough BS - time for the pictures. Sorry for the quality - I'll try to take some better ones:

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Analog out board -- I believe it is discrete:
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Power Supply:
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Copper shielding over the digital section. The lid pops right off but the board is upside down, with the components on the bottom side so there is nothing to see:
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The pot for the variable out is a big black ALPS pot - I'm thinking its a RK40 "black beauty":
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That would be perfect for my CDP-302, which has an ES quality BU-1 transport.

True but my feeling is - if your going to use a DAC anyway then why bother spinning discs (and putting hours on the laser)? I'll be using it with an Apple Airport Express streaming Apple Lossless files. Only hitch is the Airport only outputs toslink and the DAC only accepts coax, but I have a Midiman CO2 to handle the conversion.
 
My guess is that your new DAC only takes PCM. Isn't Apple Loss-Less a special format?
 
My guess is that your new DAC only takes PCM. Isn't Apple Loss-Less a special format?

Yes but the airport express puts out 16/44 PCM no matter what you stream to it so it isn't a concern. This DAC can handle 32 kHz, 44khz, and 48 kHz sample rates (all at 16 bit). The 32 kHz is nice because I have a DAT deck that can run at 32 kHz in long play mode. But it's really nice that it can handle 48 kHz since a lot of stuff outputs at that rate.
 
I've a great Sony ES catalog from this time period. Sorry, no service manual but scanned specifications and the advertising blurb.
 

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  • Sony ES DAC catalog.pdf
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  • Sony ES DAC spec sheet.pdf
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Thanks for that! Very interesting. Although not entirely accurate (at least for the US version) since it lists two transformers as a feature and mine only has one.
 
I tested it out and it works fine except for some blown lamps on the display. Any recommendations for 8-9V lamps?

I broke down and paid for the service manual. It has several tantalum capacitors. Should they be replaced?
 
Tantalums have a bad reputation when in the signal path. I've seen them in the phono section of a Marantz receiver (which sounded fine) but never tried to swap them or do a before-and-after comparison.

Otherwise, they have many good characteristics so unless they carry audio signal, I wouldn't even consider changing them. If they are, then play away.
 
They have a reputation for blowing up. I would change them. Should take a few minutes. If they are small value you can put in Panasonic stacked films.
 
Your DAC looks a LOT like my DAS-702ES, except that yours has a tape monitor button on the front panel which mine lacks, and our back panels are organized differently. I don't want to pull mine out to see, but I think mine has two sets of digital ins and outs. The 702, as I understand it, was sold only bundled with a matching transport, which I don't have. It's still a good DAC, and I think you'll find the 703 can still run with the big dogs.
 
I opened it up again to work on the lamps. They look like 4mm 8v lamps - I sent an email to AK'er DGWOJO - hopefully he can hook me up.

The service manual describes a bias adjustment. I want to check it but the bias test points have been shorted with solder. So I guess I will leave it alone. Clearly there has been some work done - the audio out board has been resoldered (very common in my experience) and there are some film caps soldered onto the fixed output jacks in parallel. Not sure what they are there for - I am trying to decide if I should remove them or not.
 
I have recently heard from another AK'er who has a US version of this DAC. interestingly, his also has the same green caps on the outputs, and the same yellow main coupling caps. So I'm thinking this was some kind of mod applied by US Service centers prior to sale for some reason.

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Long shot I know but....

I'm now getting low level crackling sounds from this thing. Both speakers. I can hear it from the built in headphone jack too so I know it's from the DAC and not anywhere else in the chain.

Any ideas? Since I'm hearing it in both channels I'm thinking maybe power supply, since the output stage is basically dual mono?
 
Hi;


A couple of years ago my DAS-703es started to sound like that.

It was caused by the DAC not syncking properly to the input signal. I traced it to the shielded digital box. The soldering wasn’t very good so I resoldered it completely. Since the component side had been covered with some kind of wax it was a bit of a hassle. Some of the wax found it’s way to the solder side of the PCB and had to be removed before resoldering.

Besides tired electrolytics in the PS it’s worth it to take a look at the soldering as well, especially parts that heat up like transistors that are mounted to heatsinks.


Good luck!



Karsten

The Netherlands
 
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