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. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    You mean these? If so, I'll have to give them a try...
     
  2. lehmanhill

    lehmanhill Almost "Made"

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    Those look like them. The getter and plates look right. Mine have CCCP in a penatagon and floating over an anvil or something. They also have a horizontal rocket emblem, but all of that is very hard to see and comes off easily. Mine were in original boxes and you can see the rocket emblem on the box.

    It was news to me, but they are highly regarded tubes and seemed very good with the SFD-1 in my system.

    https://photos.app.goo.gl/MJstouDdytJq4tBR8
     
  3. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Glad for some confirmation of my experience, and the possibility that these otherwise useless but expensive tubes may serve me well in this DAC for a while. I'm sourcing some more western bloc tubes with a trusted eBay seller, but will keep the Russkie options in mind. I think someone also mentioned Teslas?

    The tricycle thing is something I think @zerodeefex came up with in desperation when the whole custom tags thing started. I have no problems staying upright on 2 wheels, and the "wimp" part of my handle is a lame attempt at self deprecation |\/|
     
  4. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    I have tesla's in mine... they sound fine, but they are also the tubes it came with and I haven't heard any others. I'm going to roll a few others thru just to see what differences they make.

    Re noisy tubes - Upscale actually references their lowest grade tubes (driver grade) as being for dacs. I've taken that as confirmation that dacs can handle less than perfect tubes.
     
  5. zerodeefex

    zerodeefex SBAF's Imelda Marcos

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    I came up with that? That's way too clever for me. Are you sure it wasn't @purr1n or @ultrabike? I hope it was me, hah.
     
  6. ultrabike

    ultrabike Measurbator - Admin

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  7. gixxerwimp

    gixxerwimp Professional tricycle rider

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  8. gixxerwimp

    gixxerwimp Professional tricycle rider

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    So heard some noise from what I thought was the Teles installed in the SFD-1, with the amp volume maxed. But I swapped them out to confirm it was the tubes and I get the same wheezing/whislting noise (mainly in the left channel) whether I use the Teles, Valvos or EH tubes. So it must be coming from elsewhere in the DAC. It's pretty much only in the left channel, and only when the "Lock" LED is on (i.e. if I don't connect a source there's no noise). If I disconnect the left RCA analog out cable and start reinserting it, the noise can be heard as soon as the tip is touching but the sleeve is still "open".

    Any ideas?
     
  9. Azimuth

    Azimuth FKA rtaylor76, Friend

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    With no source, the mute kicks in. Sp as soon as there is a lock, the circuit is un-muted.

    I have had issues like this with op amps on DAC's in the I/V section when the power legs are properly seated. I hope it is not the analog section of the UA card.
     
  10. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I figured that's what was happening, that the outputs are basically "off" when there's no source signal.

    Do you mean improperly seated? I would think everything is hard soldered on the board. Guess I could email Parts ConneXion and ask if there's anything I can check.

    I guess this would have a chronic or terminal prognosis, with no treatment available ... :(

    If it doesn't get any worse, it's functional for my purposes. When we can travel again, I'll bring it to Toronto as carry-on and let the specialists look it over.
     
  11. edwyun

    edwyun Facebook Friend

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    Last I checked PCX had UA replacements or comparable chip replacements.
     
  12. murray

    murray Friend

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    @gixxerwimp, does the output stage use any op-amps between the D-A and the tubes? Is it only on the left and not the right at all? That sort of noise could be an op-amp oscillating at high frequency. Normal audio will still pass through, but may get some distortion. A quick test is to touch the top of the op-amps with your fingertip. An oscillating chip will often get much hotter than a normal one. Warning - only do this if it's safe and not near the high voltages for the tubes, and only if you're confident of such things.
     
  13. gixxerwimp

    gixxerwimp Professional tricycle rider

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    So I had another listen and checked out the XLR outputs as well. Right channel has a very slight hiss at full volume, which I would consider normal. Left channel has a significant amount of "whistley" "shooshing" hiss at full volume. I hadn't noticed before, but there's also a tiny bit of 60Hz hum at full volume even when no source is connected, equal in both channels (from RCAs for sure, I think from the XLRs too but I cbf'd to hook it up again*). The hum and R chan hiss is totally unnoticeable at anywhere near normal volume settings. The noise in the L chan might be borderline audible between songs if cranked really loud (far louder than I would listen).

    I found the following ICs. I don't think any of them are op amps from searching online. Everything else aside from the UA chips looks to be discrete components.
    None of them get even warm to the touch during operation.

    20210306_124709.jpg

    20210306_125139.jpg

    *The LC v1 is normally connected to the XLR outputs of BF2.
     
  14. murray

    murray Friend

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    Maybe no op amps, then. I’m not familiar with the UA modules, they may have the I/v conversion integrated and provide voltage output. It was just a possibility.
     
  15. Noodlz

    Noodlz Almost "Made"

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    So I just took a dive and picked up the sfd1 mk2 from eBay. Been wanting one of these after hearing so much good stuff.

    https://www.ebay.com/itm/203291238675

    Chatted with the seller and am hoping I can make it work. Apparently it has a crunching distortion during the first hour during its warm up, which could be mitigated by turning down the digital volume (reducing bits?) and after its warmed up you could bump the digital volume back up to full and it all sounds normal again.apparently this may be a problem with the UA chip, but it still works with the warm up procedure described (he checked pressing in on the chip lightly with a plastic screwdriver and the distortion would come in and out depending on pressure)

    on that note had a few questions after reading the thread a couple times:
    • Leaving the unit on:
      • Given that it seems to be ok after warm up, I’m leaning towards just keeping it on 24/7 so I don’t have to fuss with it. I know it was mentioned by @Xecuter that it’s not advised to leave it on, but if I did it would just be a matter of wasting away the tube life right? At 5000 -10k hours life of tubes I’d have to replace them once a year?( I plan to just enjoy this for a long while before eventually sending to PCX for repair/upgrades for caps & aes input. Will be using it via coax with my cheapo melodious mxu8 for now until pi2aes is available again.)
      • or is it more advised to kinda have a ritual / schedule of planning when to listen & warming up beforehand (seems to a bit of a hassle?)
    • Tube compatibility:
      • I’m a huge fan of the 396a / 5670 tubes, would the work in this and I’d assume I need adapters to make it work? Also, are 6h1n & 6h23n safe? 6n23P is ok right? Or stick to 6922/7308/ecc88/ecc188?
    • Physical setup:
      • Lastly this thing looks massive and won’t fit on my desk, so will probably have to put it on the floor for now until I find a solution. Any recommendations for under-desk media stands? Would a rack mount work for this?
    Excited for this and Hoping it all arrives safe and sound.~~
     
    Last edited: Mar 6, 2021
  16. Xecuter

    Xecuter Brush and floss your amp twice a day

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    @Noodlz

    It has a built in heater. The Dac sounds great after about 20 mins warm up and at 100% after about an hour. leaving it on 24/7 will not only wear the tubes out but also the caps.
    That opinion that came out of the tour years ago about leaving it on 24/7 is not really supported by anyone who has actually owned the dac. I would turn it on and off. You can also email Chris Johnson who designed the DAC and he will say how unnecessary running it 24/7 is.
    Don't be stupid and try to run adapters and weird ass tubes. 6922, 7308, e188cc, 6dj8, e88cc, ecc88 all fine. Don't run dumb adapters. Stick within the parameters that are recommended by the designer unless you know exactly what you are doing and can fix your mistakes.
     
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    Last edited: Mar 7, 2021
  17. Noodlz

    Noodlz Almost "Made"

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    Ah good point I forgot about the caps. 6922 / ecc88 family of tubes it is. I guess I’ll just have to figure out / work around the oddities of this unit once I get it. Thanks! And now to figure out where to put this monster...
     
  18. JeremiahS

    JeremiahS Almost "Made"

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    Is the noise present when using different digital sources?
     
  19. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I've tested it both direct from PI2AES and passed through the DEQ2496, but hadn't heard the noise yet. I'll check it with my iFi microiDSD as a S/PDIF source tonight.
     
  20. Noodlz

    Noodlz Almost "Made"

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    Quick question, are the xlr outs on this actually balanced? Meaning can I take 2 simple 3pin xlr to rca cables and connect it to my wa6se? Or is that still a terrible idea and I need something like the iso max 1:1 XLR > RCA converter?
     

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