Vintage DACs

Well, revel in its glory

BTW.... what happened to the 1100HD with analog stage?

Here's mine with some opamp swaps.

 

I wanted to buy it from the owner but it was not for sale. I quite like the Parasound, it's not the most resolving but has very effortless/liquid sound and the tonal balance is just perfect, it sounded more neutral to me than the Gungnir Multibit A1.

Yours really look different from his one.

 

@JeremiahS, they're both Siemens, the one on the left is an E88CC so I would presume they would be. Guess on producton is mid-seventies on, might be able to tell with better pics out of the DAC.

 

@JeremiahS , there's a lot of confusion about old tube codes and I might just be adding to it here - but the stamped characters on the metal tags can be informative. In your first photo, they look to be upside-down with A2(?) on the first (inverted) line and 7H on the second. The A is ECC88 or E88CC series (probably the latter assuming a match with the other tube; respectively would be steel pins or gold) and the 7H is either 1967 (maybe more likely?) or 1977, August.

No factory code evident, but apparently they didn't always have them - if present, Siemens Munich would be a 'not equal to' or 'sideways H'.

See http://www.audiotubes.com/mullcode.htm (scroll down to the pic of the metal tag near the bottom); http://www.audiotubes.com/PhilipsCodeList.pdf ; https://www.tubemuseum.org/SearchResults.asp?Cat=24

This looks like an equivalent fresh version from the preceding year. Tag stamps not visible, unfortunately: https://www.tubemonger.com/Siemens_Halske_60s_MINT_NOS_E88CC_6922_Munich_p/1082a.htm

 

In case anyone hasn't been following the SFD-1 thread, I have some minor noise issues with my recently acquired unit. @Tachikoma has suggested it might be the UA D20400 chip going bad. Does anyone know anything about the PCX replacement module? Is it exactly the same thing? Seems kinda bizarre they could just make their own DAC chip and have it sound the same as the OG UA unit.
https://www.partsconnexion.com/PCXDACMODULE.html

This is formerly @Xecuter's and he mentioned that it looked rather dusty inside, was possibly run without the lid on. Guess I'll have them vacuum it out when I eventually take it in for a servicing.

 

Chris Johnson with Partsconnexion was co-founder of Sonic Frontiers with one other guy. He's never stopped working on their gear and if he didn't design the chip himself you can bet he has access to the original designs.

I have zero affiliation with Chris or PC but seriously, have no fear about using them to work on your SF gear.

 

The D20400 modules contain a hybrid DAC that Dan Lavry originally designed for Analog Solutions. It's a delta-sigma chip for the low 12 bits and a manually-trimmed discrete R2R ladder for the upper 8, with a trick to prevent the MSB from toggling for low-level signals.

The measured performance was excellent in 1989, but it's not particularly special today. A form-factor replacement built with modern DAC chips might indeed sound as good or better.

 

Parasound D/AC 1500 local to me for $CAD 450. Should I or no?

It'd replace a Soekris dac1321 in a 2ch system with input from Pi2AES and a CD transport. I'd look to do the input chip and digital filter/24-96 upgrades, too, which would add another ~$CAD 200. And some opamp rolling...

 

Not a bad deal, the 1321 may surprise you with better detail (not saying it will, but it's a possibility). The XLR out on those old dacs are also "hot" i.e. loud.

 

do ittttt PCM63K DAC for cheap af, and v moddable. Brencho has the 1600 and really likes it.

 

Thanks - it's mainly curiosity to see how a vintage PCM63K unit would sound in my 2 ch system. The Soekris (your old one ) wouldn't be leaving the house, it'd transfer to the desktop while I figured out if I prefer the Parasound. My integrated is SE only, so the hot XLR outs wouldn't be an issue.

 

YES! It will likely take the CS8414 over the CS8412 for 24/96. DAC 1500 dses the SM5813AP filter chip. There also might some other op amps you could swap out. You can find a schematic for the DAC1500 very easy.

 

Just ordered a PCM63-J DAC as a stopgap until the Abbas .11SE arrives (hopefully it arrives in good working condition, and a Russian missile doesn't take it out lol).

It is the Adcom GDA 600 which I got on the cheap. It's been written abt here re: modding. It does seem like a modder's delight, almost every search for it brings up modification threads on DIY forums. I will sell here once I get the Abbas probably.

Not sure if I will have it that long to actually have time to mod it. But I might keep it as a backup DAC if I like it...

Bump this thread when you get your Parasound and have some impressions!

 

Sadly I was beaten to the Parasound. Serves me right for waiting for validation here first

Let me know if/when you want to let go of the Adcom.

 

If y'all are still looking for a PCM63 based DAC, there's two Mach 1 Acoustics Digital Decoders on eBay (I'll post 'em to the Used Deals thread in a minute). As far as I know, these were originally Monarchy Audio DACs that were heavily modded. I haven't heard them personally, but, word on the street is the Monarchy DACs are well regarded, and that the Mach 1 mods are also well regarded.

Sadly, I'm between jobs right now and can't afford to spend money on audio stuff I don't need - and especially vintage gear that may need additional cash to fix up - so if any of y'all scoop them up, let me know when if/when you're ready to move on from them!

Oh, and if you want the absolute maximum PCM63 number of PCM63 chips, there's an Accuphase DC-91 with 32 chips! 16 per channel in parallel.

 

I learned something from switching from CS8412 to CS8414 on my Theta DAC and just wanted to share for anyone else attempting do this as well.

The two chips are pin for pin compliant, but basically there is a jitter filter that is on pin 20 that consists of a resistor and a capacitor, but those values are different for each chip. Here is is on the CS81412 datasheet:

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And here is is on the CS8414 datasheet:

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It is fairly easy to find these two parts because they should be located near pin 20. Easy to ring out with a multimeter. It basically is a basic LPF on the PLL loopback on the master clock (MCK). It seems the CS8414 has a lower frequency. I have read on other forums that you can mess with this filter even more with lower value resistors (down to 24Ω) and a bigger capacitor (2.2µf). The only thing is that you might actually filter the actual master clock out, and it also takes a little longer to achieve a lock.

I did not play around with the values in my Theta DACs. I saw they were set to the 1KΩ resistor and 0.047µf value for the stock CS8412 chip, so I put in the 470Ω and 0.068µf.

I also read somewhere to not use ceramic caps for this purpose unless it was a certain rating and the datasheet suggested using a film cap for this. So I put in an MKP film cap, and it sounds great. A drop in CS8414 should work to lock at 24/96 as a drop in replacement, but this is just a change to help with jitter. My guess is with higher incoming sampling frequency they wanted to tighten up the jitter.

 

I now remember about the ceramic capacitors. It actually was on the DIR9001 datasheet, which had a different, but very similar configuration on the filter as the CS8414.

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Anyways, it says in the datasheet: "Film capacitors, with tolerance is less than 5%, is recommended. If ceramic capacitors are used for C1 and C2, parts with a low voltage coefficient and low temperature coefficient, such as CH or C0G, are recommended."

It also says: "Film capacitors, with tolerance is less than 5%, is recommended."

 

Has anyone heard the Perpetual Technologies P-3A with or without the P-1A "digital correction engine"? There's one on the audiokarma subscriber section with a monolithic sound linear PSU for $425 - The P-1A does upsampling and DSP stuff and the P-3A dac uses the Crystal CS4397 chip, which sounds cool in write ups from stereophile, but so does everything. Just wondering if any actual people have heard it.

 

This is actually referred to as 'loop filter' on diy sites and lots of people recommend different values from stock to optimize this filter. One of the most popular mod was called 'wildmonkeysect loop filter mod' and I have used it with CS8412 in my Adcom gda600.
I have always preferred film caps esp. polystyrene to ceramic ( even c0g) caps in listening tests and prefer to use them where size permits and lead length is short enough.

 

This?

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That is a bunch of caps on the power supply side. Like one other poster pointed out, may be over doing it if you already have separate digital and analog power supplies (I know my DS ProBasic II does).

And that would be a lot of caps to pack on the board already.

One other thing. I noticed that the Theta DS ProBasic II actually has the capacitor before the resistor. So the resistor is what is connected to ground and one end of the cap is connected to Pin-20. Not sure why this is.