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TOUR: MHDT Labs Stockholm V2 NOS DAC tour! PCM56P-J R2R D/A chips, Bendix 2C51 Tube, 24/192 input

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  1. ruthieandjohn
    What is a "Bimby?" Thanks!
  2. Luckbad
    Schiit Bifrost Multibit.
  3. Barra
    Sad day, but the S2 is going away tonight. Torq takes it from here. I am going to miss it.
    Interesting results on the speakers. Sounded great, but didn't get a chance to dial it in as the frequency response was all out of wack compared to Havana or my normal DAC. The S2 was putting out some serious bass that really needed adjustment. It goes to show how much the additional grunt adds to the signature. However, to adjust for the added bass would have taken away from the music night, a bit to much effort, so we left it as is. The additional bass without adjustment stepped onto the mids and collapsed the size of the sound stage compared to the optimized HP setup. The airiness was gone. Even with all those issues, it was still very enjoyable. 
    Luckbad likes this.
  4. jaywillin
    and the journey continues
  5. Torq
    Just took the hand-off from @Barra.

    Everything looks in good condition, but won't get a chance to fire it up and start listening until tomorrow (Tuesday) morning.


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  6. Torq

    Overall Impressions:

    I found that MHDT’s product had a little bloom to the bass, which was especially noticeable via my WA6 – in fact with this pairing the bass was a bit overpowering, a little too fat and lacking in some control.  The Stockholm was slightly recessed (that might be too strong a word … but it was not as prominent as with the other DACs I used) when it came to deeper female vocals and yet managed to be a little sibilant with some of the brighter female voices (in places I’m not used to said sibilance).
    Treble detail seems excellent and has a little extra sweetness to it compared to what I’m used to.  There’s a nice sense of space and air and things don’t get muddled when there’s a lot going on.  This never got fatiguing and had me exploring piece after piece that benefits from a delicate, sweet and detailed handling of the upper mid-to-treble range (primarily small ensemble acoustic stuff).
    I imagine the tube-DAC feeding tube-AMP configuration here is responsible for much of the low-end bloom and the extra treble sweetness.  These elements were still audible, but much less pronounced, when played through my Ragnarok, though the bass prominence and plumpness was still quite apparent with my speaker rig.
    The soundstage I found to be quite expansive and, when paired with speakers, nicely three dimensional (more on that in a bit).
    Overall I found the Stockholm v2 to be very musical, possessing a lovely sweet and detailed treble and, paired properly amp-wise, a very satisfying if somewhat warm bottom end.  The mid-range was lucid and engaging and the overall instrumental tone was beguilingly rich.
    I didn’t get to spend any time rolling tubes but I imagine that doing so would make it relatively easy to adjust the bass suitably, bring out the upper female vocal range a bit and maybe round off the little bit of unexpected sibilance on some (not all) higher pitched vocals.
    Despite the fat and somewhat less-controlled sounding lower registers with the WA6 pairing, I found myself listening well into the small hours with the Stockholm, WA6 and HD650.  A slightly leaner tube would improve that further and I think it’s a wonderful combination.  Not that I mean to suggest the MHDT product is limited to that end of the gear spectrum, it was a lovely listen through my Ragnarok as well, but I found it to be particularly musical and engaging with the WA6 and HD650.
    Compared to the Chord Mojo:
    The Mojo is definitely more neutral, exhibits none of the Stockholm’s slight de-emphasis in the mid-range, has a much more even, taught, detailed and controlled bass, didn’t exhibit the sibilance I found in the Stockholm but also lacked the upper-end sweetness and generally juicy sounding mids.  Also, I’d give the Mojo the upper hand from an imaging perspective both with headphones and, particularly, with speakers.
    So … while more accurate and more detailed, the Mojo drew me into the music less than the MHDT unit, unless there was a lot of energy in the female vocals or the bass line was particularly deep and driving.
    Big orchestral pieces favored the Mojo, partly for it’s imaging and partly because it provided better separation between instruments.
    Compared to the Bifrost “4490”:
    The Schiit unit is much drier and more controlled, but no less extended, in the lower registers, flatter through the mids and ess interesting (though probably more accurate) in the upper-mid to treble regions.  Feeding the WA6 it was the most neutral presentation excepting the Yggdrasil, but was a bit less engaging for it.
    I felt the MHDT was letting me experience more of the nuance of voices than the 4490, and then, through the Ragnarok, the 4490 seemed a bit harsher and less forgiving with anything that wasn’t extremely well recorded.  The Stockholm was, also, a more pleasant listen with lossy source material.
    Texture and timbre of instruments are more natural, to my ears, with the MHDT DAC than with the “4490”, and notably with woodwind and string instruments there’s a little extra richness to the tone than I find with the Schiit component.
    Compared to Yggdrasil:
    This is a rather unfair comparison.  The Yggdrasil is the best DAC I’ve yet heard - and that list includes some very much more expensive gear.
    The MHDT piece doesn’t do badly here at all, but it doesn’t have the detail, neutrality, ability to, somehow, make everything in the mix seem to be the focus all at once (not technically possible, of course, but I don’t know how else to describe it), that Yggdrasil has.
    Soundstage/imaging out of the Yggy is out of this world.
    In some places the Stockholm is a bit more “fun”, and it is more forgiving of poor recordings/lossy encodings, and there is some artificial sweetness or lushness in places that make it a cozier listen … and that’s very desirable at times – but it’s not as truthful or, overall, as satisfying as Schiit’s monster.
    With Speakers:
    My speaker system projects a very palpable, three dimensional, sound stage.  The Stockholm was able to play to this very nicely and, I think, does a better job there than even the Akurate DSM that is the primary source for that system (at about 10x the MHDT units price).
    While I think the Mojo just edges out the Stockholm on overall imaging and instrument placement, it’s pretty close.  Only Yggdrasil is convincingly and obviously more capable here, fixing things in solid positions with no drift and no question as to what is where.
    Another facet of my speaker rig is the active drive with active crossovers and eight independent channels of amplification with an Isobarik bass configuration.  This system doesn’t need subwoofers at all, and with the MHDT and the stock tube it was overpowering and went beyond bloomy into overdone and boomy.
    Using USB:
    My use of USB audio is entirely limited to portable scenarios, either with my 12” Retina Mac Book/15” Mac Book Pro or my iPhone/iPad.  As a result, I don’t own/use any USB re-clockers, conditioners or isolators.
    Driven directly from the 12” Retina Mac Book I found the results with the Stockholm to be a mess; timing seemed way off, brass instruments had an unusually harsh edge, and it was not a pleasant listen at all.  The Mojo had no such issues here, nor did the Yggdrasil.  Using the Mac Book Pro, Mac Pro, iPhone or iPad as USB sources exhibited no such problems, so I’d chalk this up to the Stockholm being more sensitive to the quality of the USB source than some other units.
    Of note, my Bifrost also suffered when fed with the Mac Book – but not to nearly the same degree.  Whether this is something to do with the CM6631A USB interface (common to the Bifrost and the Stockholm) or the way each device implements it I don’t know.
    USB cables were all AudioQuest Cinnamon, with terminations appropriate for the target DAC.  I did try the cable included with the unit, but it made no difference that I could hear, so stuck to the ones I generally used.
    General Notes:
    The vast majority of my listening was done feeding the Stockholm v2 via TOSLINK (with a Lifatec glass cable), from a Mac Pro running the latest version of Audirvana with a combination of lossless Redbook CD rips and various 16/44.1 to 24/192 KHz HDTracks/Linn Records downloads and TIDAL for other 16/44.1 material.  I used Spotify for some lossy-listening evaluations.
    My Bifrost is a very early unit, upgraded to the “4490” board and has the USB Gen 1 board in it.  It only had USB in it at all as a “just in case” measure, so I never bothered with the Gen 2 upgrade.  This is the first cause I’ve had to use that interface for any kind of critical listening.
    I listened using AKG Q701, Sennheiser HD650 and HD800S, LCD-2.2c and Abyss headphones.  My general impressions remained constant across those headphones.  With the AKG Q701 the plummy bass of the stock tube in the MHDT was very welcome, where with the LCD-2.2c and Abyss it was too much.  The LCD-2.2c and HD650 responded particularly well to the sweet and detailed treble of the Stockholm, but the Audeze’s weren’t such a good match, regardless of amplification for the MHDT unit’s slight deeper vocal recess.
    Amplifiers used were my WA6, original Lyr, Ragnarok and, for speakers, an Akurate Kontrol/1 with dual Akurate 4200 power amplifiers.  All exhibited the same, fundamental, signature with the Stockholm, the the WA6 definitely emphasized the bass bloom and treble sweetness.

    Personal Conclusions:

    One of the most interesting aspects of this tour, for me, was the fact that I have been trying to decide upon a DAC to permanently pair with my WA6 – which I bought a) to let me play with a pure-tube amplifier and b) as a dedicated bed-side rig.  For a while I’ve used the Mojo to feed it and that’s been very nice and it was going to come down to that and either a multi-bit Bifrost or I’d repurpose the 4490 for the WA6 and replace it with a multi-bit model.
    As things stand my intention is to put a Stockholm v2 with my WA6 and find a tube that tightens/lightens up the bass a bit and make it the mainstay of my secondary stack at home.  It fit particularly well there with the HD650 and did a nice job with the HD800S, and it’s sweet but detailed treble and rich tone treat acoustic pieces in a particularly lovely manner.
    It’s an engaging, detailed and still completely relaxing listen there, while also being able to exhibit drive and pace and solid rhythm with more neutral amplification/headphones.  I would not describe the MHDT as overly euphoric … but it tends more towards euphony than towards being utterly technical.  It doesn’t skimp on detail at all.  A very satisfying middle ground, I would say … most of the best of tubes and solid-state combined.
    Value seems very good, and the ability to tune the signature with a solid array of alternate tubes makes it particularly interesting and flexible.  Loved the musicality of the thing and I’ll definitely miss it until mine arrives.
    No doubt I’ll remember things I wanted to mention the moment I post this, but I’ll update if/when that occurs!
    Many thanks to @Soundsgoodtome for arranging the tour and letting me participate, and a very nice job from MHDT with a very musical and entertaining product!
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    s1rrah, grizzlybeast and Luckbad like this.
  7. Soundsgoodtome
    Excellent write-up and impressions Ian! I think you've got the signature down. Although I'm wondering if there's an issue with the tube, it seems uncharacteristic for the Bendix to have a loose bottom end that you and Bill have found. I will PM @ericr and see what he thinks of the tube compared to his other Bendix. Highly appreciate the quick input and great comparisons. Cheers!

  8. RCBinTN
    That is the most impressive review I've read in a long time, @Torq.  Fantastic job.
    You have a lot more gear that I do, I'll just be comparing against my GMB and BHA-1, no speaker rig to compare against.  
    Looking forward to the comparison between the Stockholm and my Gumby!!
  9. Luckbad
    Excellent review. While I haven't heard the Stockholm, I've heard the Bendix in the Pagoda and Atlantis.

    The occasional sibilance is likely the tube. It's the price you pay for that tube's excellent detail.

    I doubt it's responsible for bass bloom unless the tube is wearing out.
  10. Torq
    I appreciate the kind words!
    Hard to say if the bass is a worn tube or not as I don't have another to compare with - @Soundsgoodtome would have to comment on whether its a "new" tube or not.
    The bass bloom was less noticeable with the Ragnarok and Lyr.  The WA6 isn't something I'm used to hearing as overly emphasized in the bottom end, but my speaker system is certainly very potent in the bass so it's possible it's magnifying any emphasis there.
    The lovely treble was quite apparent across the board though and you'd have to consider me a fan of that presentation when I'm listening to lose myself in the music!
    I'm now starting to do research on other tubes to play with when my own Stockholm v2 arrives ...  [​IMG]
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  11. Soundsgoodtome
    The DAC is on the move, off it goes to Portland. I'm hoping that the shipping estimate is off as it's showing Thursday delivery but all ground services I've shipped to Portland before took 1 or 2 days, not 3. If it does get there by Thursday however I don't think it'll make the meet @JoeDoe. I may have to get give @Greed some moneys to 2-day or overnight it to @kayandjohn to make time, we'll see how it works once it gets to San Diego.

    On another note, I've emailed Jiun at MHDT Labs in regards to the slight bass boost and he's saying there's a possibility that the DAC chips may have come loose from the socket during shipment. Although a slim chance, it should be more than just a subtle change so highly unlikely this is it. Here's his response verbatim:
    Hi Andrew,
    Stockholm does not has loose bass problem.
    Try to press PCM56P-J chips downward a little bit to firm the chips again.  They may lost some connection/contact to its socket during transportation.
    (in regards to my question of the Bendix 2C51..) The construction of 2C51 is different to 5670.  If you watch carefully when these two tubes light on, you will see the filament of 2C51 is hanged in top ot the tube while filament of 5670 is hanged in the bottom of the tube.  They are also with slightly different current consumption. These difference tend to make 2C51 in favor in bass response than 5670's.
    I don't know if your Bendix 2C51 is good or not.  Better to change tube to see what's happening.  If my memory was correct, Bendix 2C51 was OEM by National tube and  specially selected by National.
    Best Regards,
    Mhdt Labs

  12. grizzlybeast
    could give first listen impressions already with the Nuprime HPA-9 but I will hold off a bit. 
  13. Soundsgoodtome
    Very nice!! I spy HE800S and Audeze LCD2s in the background. Which ZMF phones are those?

  14. Soundsgoodtome
    Looks like the differences in gear may not play to the tube I've originally fitted the Stockholm 2 (Bendix 2c51). So in light of this I'm sending to the tour two additional tubes, one is the AEG 5670 which a long time Stockholm owner finds to be one of his favorite (thanks for the tube rolling tip @S1rrah). The other tube is the GE triple mica that MHDT are now providing with their DACs.

    The AEG 5670 has the air, soundstage, balance, bass end, and is essentially a sound clone of the $180 Bendix 6385. The GE triple micca is a smoother sounding tube with richer tube-like sound, this is a step up from the original stock double micca GE and is very affordable.

    To swap tubes it is important to power off the DAC before removing/replacing, otherwise the DAC can be damaged. Allowing a cold tube to warm up for at least 5 mins before running music through the DAC will prolong the tube's life, optimal sound doesn't come until ~30m of on time anyways.

    I've also included a test CD with tracks that I find sound fantastic. Some binaural, red book, and hi-res. It is what I que for my systems when I attend meets; because you don't test drive a sports car on a bumpy road, the music has to allow the gear to show what it's got :) The CD is for testing only, I fully expect it back with the tour, please do no make duplicates.
  15. s1rrah
    @Torq ...
    Really interesting write up on the Stockholm; I find your comments to be very accurate in regards to my own experience with the Stockholm 2 DAC over the past year or more.  In fact, your comments could easily describe the Havana 2 DAC as well ... 
    Your comments on bass performance echo my own in a couple different reviews I've done of the MHDT DACs ... compared to other DACs I've owned/borrowed, the bass on the MHDT Dacs has always been just a bit loose around the edges ... something I would never notice until direct A/B listening with other gear.  I'm not so sure this is a tube anomaly as much as it is related to some other factor (perhaps capacitors used throughout or some other nuance of the circuit); the Bendix 6385 and 2C51 tubes will certainly do a bit towards tightening up the bass a hair but I wouldn't call it a "transformation" by any means.  Similarly, an AEG tube will do the same (but good luck finding one).  But the slight "bloom" in the bass is by no means anything glaring and is completely offset by the DACs other stellar qualities (musicality, ease, richness, etc.).
    The Pagoda DAC, an identical circuit as the Stockholm 2 ... with it's PCM1704 DAC chips, creates a markedly different image sonically than the Stockholm 2 ... and while the bass is a tad leaner/tighter ... it still occasionally has that "trademark" MHDT "bloom" here and there ... which is what leads me to believe it has more so to do with the other components in the DAC (capacitors, etc.) more so than the tube or general R2R design scheme employed.
    As mentioned, the Havana DAC has even more of this quality ... being a significantly "darker" listen than the Stockholm 2 ... but many users in the long standing Havana thread here at Head-fi have *extensively* modified their Havana DACs putting in different power supplies and in some cases completely replacing all of the MHDT Labs produced capacitors with high end, very expensive "boutique" capacitors and in such cases the consensus is that the DAC was completely transformed in to a far and a way more high end listen by said modifications (bass included) ...
    I'm no DIY guy, though and so I won't be modifying a Stockholm 2 DAC any time soon but perhaps somebody will; and regarding this, if anyone is interested in such mods ... just spend a lot of time in the Havana thread and pretty much anything you see there will apply to the Stockholm as well ...
    But thanks again for the comments ...
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