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

Do you know how much it costs to replace all the electrolytics in SFD-1 mk2? I just picked up a unit to play with. Should I be worried?

 

The only electrolytics that have actually failed on my SFD-1 are C501 and C502. It's likely that they have failed on others as well, based on the stories of problems. So, the timing circuit is a crap shoot that could leave you with a dac that doesn't turn on, but overall the other electrolytics haven't caused an issue that I know of. That said, the dac is more than 30 years old and electrolytics often fail with age. The electrolytics in the SFD-1 are, from what I can tell, primarily in power supply smoothing or timing duties, such as C501,C502, so I don't expect a change in sound.

But to answer your question, buying the parts, mostly from edwyun's list in post #261 of this thread, the electrolytics are about $40 plus shipping from partsconnexion. If I were you, I would listen to the dac for a while and decide if you think it's worth the time and effort to update and upgrade parts. And if you like it, read this thread about tubes because the right tubes really make a difference in this dac. The right tubes took mine from pretty good to "Oh yeah!".

 

This is good information. Thanks! What is your sound preference and which tube did you end up with?

 

I like Soviet 6H23N, but others have different preferences. It's a synergy thing with the rest of your system. I was lucky to get some of the "rocket" Volkshod 6H23n's before they became expensive, but the "Reflektor 6H23N-EB sounds almost as good. Parts Connexion has matched pairs of those for $133 for the pair, which while not cheap, is about as good as you can do. For me, the now common Matsushita PCC88 was dull and uninteresting in this dac. At least in my system.

By the way, my SFD-1 is in a system with Linkwitz LX-mini speakers and those use a 3" for mid and high frequencies. It sounds good, but I always wonder if I am favoring other components, like the 6H23N tubes, because the speakers don't have the high frequency extension that a different type of tweeter might have.

Another thing. I hinted that C501, C502 were in a timing circuit, but I didn't explain. The SFD-1 needs a few seconds of power on the tubes for the heaters to warm up. C501 and C502 are part of a delay circuit that doesn't connect the output signals until the tubes have warmed up. If the caps fail, the circuit delays until the caps are replaced. The good news is that mine started out intermittently disconnecting, so I had some warning if I had been smart enough to act on it.

Finally, getting the main board out to replace any caps is a pain. If you choose to replace any caps on the main board, you would be wise to replace all the main board parts you can think of so you don't have to do that twice.

Have fun.

 

These DACs are very robust. So if the DAC is playing music without fault (e.g., staying in standby mode, crackling in one/both channels), I would not worry and do as lehmanhill says and just enjoy. If help/repair is needed, you can always contact or send your DAC to PCX.

 

Except the Mundorf caps (C14, C16, CL14, and CL16) in the output/tube section. Money well spent for better LF.

 

Mine came with the Mundorf already upgraded, so I never got to hear the difference, but I totally agree. They are in a position to truly influence sound.

Just a clarification, the Mundorfs that edwyun is referring to are film caps, not electrolytics, so the caps in C14, C16, CL14, CL16 are probably good as they shouldn't age. The Mundorf change is a pure sound upgrade.

 

I just bought a PCX serviced/upgraded SF-1 mkii and it only has two Mundorfs in the output (?) stage. This is the first I’ve seen like this.
The question is if it is worth DIY or sending in to complete the other half?

EDIT: After hearing from smarter people, it looks like the Mundorfs are in the RCA outs and not in AES output stage.

 

It is a lot of legwork to get the PCB out to change those caps. Why in the heck it wasn't done when the other two were done is just silly; the cost of two additional caps is like $40 for the two, the labor itself is the same.

 

Ready to get back-up in mine? @Mr.Sneis did the analog side upgrades for me. Vishay nakeds and some nice caps that we swapped out. I'm not sure if I still have finished form photos. I've only swapped in some nice tubes since then and everything has been great except for sometimes not getting a lock on AES.

Currently running it both SE and BAL through the Freya N, but not sure if the SE is needed since the Freya N seems to run BAL in SE out.

 

Agreed. Also, it looks like only some resistors were updated with wire wound resistors (just below the tubes) and only some resistors were updated with AMRGs (just above the relays near the outputs). Must've been a reason.

 

One thing I've noted having the SFD1 MkII and the Processor 3:

My SFD has the AES input instead of the Toslink input, so I can't connect a 4K TV's Toslink output to the SFD to decode and hear the audio from my TV. Tried a Toslink to Coax/AES converter. No dice.

The Processor 3 of course has all manner of inputs, including Toslink. So I am able to connect my 4K TV to the Processor 3, which decodes the audio at 48kHz. Nice that it works.

 

Vishay nakeds? Can I assume these are where the AMRGs normally would be? Nakeds and AMRGs are both nice resistors, but quite different. I had just gone with the AMRGs because they were apparently used in SE upgrades and I assumed complimented the sound signature that PCX wanted. Does anyone have experience with Nakeds in the SFD-1 and can comment on how they affected the sound? I can guess based on past experience with Nakeds, but actual experience would be great to hear.

Also mentioned were some "nice caps". Can you tell us more? Mine came with the Mundorf Evos and, although nice, they are not my favorites, at least in other applications.

It looks like the wire wound resistors are connected diagonally. That's interesting. Maybe to get more air around the resistor for cooling? Lots of interesting choices on this one.

 

Could I get some eyes on my unit and let me know if I have any update/upgrade in my unit. I honestly don't know much of this dac other than the most basic stuff - the other 21 pages will be my weekend reading







Edit:
1. Could someone tell me what kind of tubes are these?
2. Do you typically leave this on 24/7 or turn off after each use?
3. I just want to echo someone here who said this dac "sounds like f'ing music"

 

Looks stock to me, but it's hard to see the resistors. Output caps are for sure stock.

 

I agree, pretty much stock. The only modification that I see is that someone seems to have put some damping material on top of the transformers. Not a big deal.
You have lost the labels on the dac modules. That is quite common because time and temperature have caused the label's glue to fail. Also not a big deal on a 30 year old dac.
The build is probably later than mine. That's based on the blue caps, ERO MKP 1841. The ERO caps are 0.56uF where mine are 0.22uF. Some of the SE upgrades have 1.0uF Wima MKP4, so it looks like they were increasing the value of these power caps over time. The ERO caps are nice enough caps, so don't feel like you have to replace those unless you just have to have the 1.0uF.
You also got the AES input. Early ones like mine have an obsolete optical input instead. By the way, the idea that it might be a later build gives you some age cushion on the electrolytics.

 

Reflektor 6H23N-EB is on sale at Parts Connexion for $106. I decided to pick up 2 pairs given I know nothing (or rather don't remember) about tubes and I tend to leave my equipment on and forget to turn it off. I don't know what tubes I currently have so if someone could identify that for me that would be very helpful to have as a reference.

update: the sound of SFD-1 is glorious, rich, open, big, transparent, holographic, micro details, macro dynamics, PrAT, bass slam/weight - it almost feels like I am cheating the hifi game. The transport is Emm Labs NS1 via AES (okay, the transport is over 5x the cost of the dac, so that could have contributed something to the sound).

 

I got the Reflecktor yesterday and it has been non-stop listening since then (improvements in bass, holographic nature and midrange resolution). Lol...SFD-1 with the new tube makes my Emm Labs sound like a smaller upgrade than the price difference would otherwise suggest - I think 2channel will make the improvements more obvious but I am not about to mess with my 2 channel. I am waiting for new power cord and AES cable from Audio Envy. Fingers crossed for another jump in quality. I am not ready to provide any impression due to too many moving pieces.

Does SFD-1 make Chinese R2R dacs a waste of money at this point unless high res is absolutely required and you are not willing to use Roon to resample?

 

I resample if need be. I haven't found a situation where 24 bit broke my spirits. Tubes to make a small improvement - modifications on the board make even more of an improvement (IMO)

 

Hmm I’m not sure. Properly designed one like the Holo DACs plays at a really high level, even if for some reason you don’t want to use software upsampling.