Sonic Frontiers SFD-1mk2 Vintage DAC for $750 That Stomps Most Modern DACs

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by purr1n, Nov 9, 2015.

  1. caute

    caute Lana Del Gayer than you

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    I've read a relatively unknown guy whose ears I—and others here—trust, a reviewer of all things valve-related who goes by the name Dr John, prefer the SFD-2 mkI (yes, the mark 1, without the HDCD decoding) to the mkII.

    As well, he actually preferred both versions of the SFD-2 to the Sonic Frontiers Processor 3, so take that for what you will.

    SFD-2 may or may not be the pinnacle of Sonic Frontiers D-A tech, but it's certainly not the end of Ultra Analog in particular (ML comes to mind) or vintage DACs in general.

    You still, for instance, see DACs floating around (there's actually one in "as is" condition right now on eBay) with the very well-regarded PCM63(K) chip in them, like the thunderous low end slamming and analog warm Theta Gen Va.

    Edit: The Theta Gen Va was designed by Moffat, and it was top-tier for its time, so it’s basically a Yggdrasil come 20 years early.

    The thing abt SFD DACs tho, is while they are vintage, they are still, as everyone ITT knows, serviced by PCX, the original makers of the DAC.

    W other vintage DACs, you lose out on that peace of mind, support and also any upgrade paths.

    How handy you are w a soldering iron and your knowledge of electronic circuitry matter that much more w a Mark Levinson, Theta or Monarchy.
     
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    Last edited: Apr 25, 2023
  2. lehmanhill

    lehmanhill Almost "Made"

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    That's becoming a typical failure point for these, but it's not surprising that a couple of small electrolytic caps would dry out after 30+ years. The biggest pain will be getting the board out of the chassis to solder in the new caps.
     
  3. KenAR

    KenAR Acquaintance

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    Yeah, while I wait for the two caps to arrive I started to prep and will need to desolder every digital input and the sole BNC output before removing the board. Not a big deal, need to mark which wire goes where so I tool some pictures to make sure I re-wire them correctly after the cap swap.
     
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  4. caute

    caute Lana Del Gayer than you

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    Anyone know the procedure for taking out the board? @famish99 gave me the steps, but wondering if they go in a certain order. Also looks like no desoldering is involved in getting the board out? reason: wanna replace some caps on it.
     
  5. edwyun

    edwyun Facebook Friend

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    Anyone compare the original D20400 DAC modules with the PCX replacement D20400 modules?
     
  6. RestoredSparda

    RestoredSparda Friend

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    Yep, and then it's a very tight fit to get the digital input board gently bent forward in order to pull the motherboard out of the chassis. Go gently but also forcefully if that makes sense, and at an angle.
     
  7. edwyun

    edwyun Facebook Friend

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    If I remember correctly, you have to desolder the short wires from the output board to the RCA and XLR jacks and the AES/EBU digital input (if you have it). The coax and bnc digital inputs can remain on the small PCB. Just unscrew the nuts that hold them to the back plate.
     
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  8. KenAR

    KenAR Acquaintance

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    I thought so too on the nuts for the BNC and Coax inputs, and Coax outputs. As you can see in this picture I was unscrewing the nut of the Coax and it turned inside and snapped one of the wires. The outside nut is only there to hold the jack in place, the inside nuts are the ones needed to unscrew. You can also see the AES is partially blocked due to its size, so that will also require a desolder. I took lots of pictures to make sure I wire it up properly when putting it all back together.
     

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  9. edwyun

    edwyun Facebook Friend

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    Ahh, it looks like you are talking about the SFD2 (I was referring to the SFD1). Yup, you do need another wrench on the inside to unscrew the nuts on the outside. It also does looks like you will have to desolder the AES/EBU input from the board.

    They improved this on the Processor 3 in that desoldering is not needed at all.
     
  10. KenAR

    KenAR Acquaintance

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    Yeah, an SFD-2 mkii unit. Still waiting for the replacement caps to arrive so have been prepping to be ready to go!
     
  11. caute

    caute Lana Del Gayer than you

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    Has anyone DIY replaced the four coupling caps in the output section, that can also walk me thru the process?

    I mean, from desoldering the AES input and getting the board out to work on to actually replacing the caps?

    would really appreciate some help, I do have the advantage of having my dad, an ex-EE to help me, but I’d like to learn how to do these things on my own, too, plus I’m not too sure how to get the board out even, even if the cap rolling is easy.
     
  12. caute

    caute Lana Del Gayer than you

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    Can anyone tell me with confidence that in or around 2015, PCX sold replacement UA D20400 DAC modules for SFD DACs?

    As of today, they only sell AD1862 drop-in replacements for their old DACs, but I don’t want those chips.

    reason I’m asking is I’m looking to buy an SFD-2 that has 7-year-old PCX replacement chips in them, and I’m wondering if:

    1. they’re legit UA D20400
    2. If they sound the same as the OG modules

    These are not pulled from another UA DAC like a ML or something, which I believe PCX also used to do, it looks to be made specifically either by or for them. So If anyone has any experience with these chips, please let me know.

    (Edit: for context, I’ve emailed 3 different PCX addresses starting over a week ago asking this same question but have not gotten a response from any of them, hoping someone here can sleuth it out.)

    here’s the reference pic:

    [​IMG]
     
    Last edited: May 24, 2023
  13. loadexfa

    loadexfa MOT: rhythmdevils audio

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    This doesn't answer your question but for what it's worth, my SFD-2 had the DAC chips replaced by PCX before I bought it (recently enough that it's not the UltraAnalog chips) and when I compared it to the SFD-1 with an UltraAnalog chip I thought they both had the same house sound with the SFD-2 being less warm and way more resolving. The SFD-2 being less warm matches what others have said even when it has the UltraAnalog chips.
     
  14. caute

    caute Lana Del Gayer than you

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    That does track with the general sentiment I've read here, sfd-1 vs 2, gives me some heart. So did your DAC come w replacement modules or did they fail and you sent it in to get replaced with whatever they had in stock? Either way, this is interesting, I wonder what chips you have...
     
  15. loadexfa

    loadexfa MOT: rhythmdevils audio

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    They were replaced before I bought it, the previous owner had the DAC upgraded to SE+ and the chips needed replacing at the same time. I think he sent me the details but I can’t find it. @archer88 do you remember? (I bought the SFD-2 from archer88).
     
  16. KenAR

    KenAR Acquaintance

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    What DAC modules did it come with? My SFD-2 mkii is still with PCX, they have it in their queue for repair and hope to get to it by next week, fingers crossed....
     
  17. KenAR

    KenAR Acquaintance

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    While I don't know about 2015, but do recall seeing the UA modules available as late as 2022 on their website. They had a white label but where the D20400A modules.
     
  18. loadexfa

    loadexfa MOT: rhythmdevils audio

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    I couldn't say, that's before I bought it.
     
  19. loadexfa

    loadexfa MOT: rhythmdevils audio

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  20. caute

    caute Lana Del Gayer than you

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    Used the waybackmachine to check check PCX.com from 2015 and 2022, and this is what came up under replacement parts for Sonic Frontiers DACs:
    [​IMG]
    Is this what you meant by a "white label"? or is this pic just in black-and-white? cuz it looks v similar to the gold replacement DAC chips in the SFD-2 I imgur'd.

    It looks like sometime between 2022 and 2023, they switched to the AD1862 replacement chips that @loadexfa has in his SFD-2. But I'm still not sure what chips are inside this module... They even have different product SKUs, the one above is "PCXDACMODULE" and the other two (one with Sparkos opamps for IV and IV done by Monolithic in the cheaper one) have different SKUs.

    One thing that gives me some hope is that the OG UA D20400A chips were hybrid, meaning the modules included both DAC chips and IV inside (the Processor 3 or "SFD-3" has them separated, and the designation on the DAC chip in that converter is D20400N standing for "naked") and in this pic and in the SFD-2 DAC I linked in my above post show a chip that looks very much like the OG one, stylized the same, a smooth rectangular, flat module (and likely even epoxied on bottom, like the OG).

    The reason the new AD1862 modules (SKU: PCXDACP-8950X) look radically different is bc an opamp change is necessary for the DAC in question to actually run when swapping DAC mfrs and models in a drop-in situation.

    [​IMG]

    So this leads me to believe that the replacement modules from 2015 (and likely much earlier, I just only checked 2015 bc the DAC I'm looking at buying has what can only be a date code of 07-2015 written on it) to early 2022 are indeed some type of Ultra Analog chip, a new production of the original D20400A.

    But how PCX was able to sell one of these for only $250 is the only thing that still has me worrying. Setting up a whole new production line just for replacement chips must be expensive—unless these chips were pulled from working units and merely given a facelift—$250 is a pittance for what is regarded as one of the best R2R DAC chips of all time (with the PCM63K, particular Analog Devices models, the pictured AD1862 included, and for some, the TDA1541A S2 fighting it out for total supremacy).

    If my thinking is off here, or I made a deductive error, please let me know. While I'm sure the AD chips sound great, I just want that UA sound, and want to make sure what I'm buying has the goods.
     
    Last edited: May 24, 2023

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