Schiit Gungnir DAC

Discussion in 'Dedicated Source Components' started by warriorant, Mar 29, 2012.
  1. Friscosfoe
    It felts like the Gumby has more authority (gain?) and more delineation. For example, if I can offer an analogy between sound and distance. I’m listening to Renee Fleming Christmas album in hd. On one track the bimby expands the seperation between her voice and another female singer to let’s say an inch. With the Gumby the distance is two inches.
     
  2. Don Quichotte
    I see. The tonality and frequency extension are identical?
     
  3. KeithEmo
    I haven't seen the Gumby's schematic, but a lot of devices mute their outputs at various times by shorting their output to ground using a relay.
    Odds are the output of the DAC is shorted to ground when there is no music playing.
    (This is a perfectly normal and safe thing to do.)

    Because of this, if the DAC is producing a DC offset at its output, you can expect that offset to go away when the output is muted.
    And you can also expect a big pop when the muting goes on and off.
    (The pop you hear is the DC being shorted and unshorted suddenly; the noise occurs when DC is applied to a volume control which is slightly crunchy to begin with.)

    However, you would see those exact same symptoms if the output of your DAC is connected to another device, and there's DC leaking back out of the other device's INPUT circuitry.
    (If that was the case, however, this would only happen when that other piece of equipment was connected.)

    Of course, neither should be happening.

     
  4. Don Quichotte
    @KeithEmo : Yes, this is exactly how I understand the phenomenon too.
     
  5. Don Quichotte
    Something else occurred to me. Please, can a few of you measure for any DC offset on your Gumby's unbalanced outputs while playing music and post your result here? All you need is a voltmeter and less than 1 minute available. I'm thinking that my left channel's DC offset is not entirely normal either - at about 84 mV it seems too high to me, although it didn't cause any problems that I was aware of.

    Generally speaking, what do you think would be an acceptable level of DC offset at the output of a dac or CD player?

    I'd much appreciate any info on this topic. Thanks!

    Edit: For example here (scroll down to the end of the first post) 16-50 mV is considered acceptable for an amplifier, while the Gumby's offset is further amplified by the amplifier (if DC coupled) before reaching the loudspeakers / headphones. And a few years ago I asked AKG and the designer of AKG K1000 what is the acceptable level of DC offset reaching these headphones' drivers and was told something along the lines of (iirc): "pretty much because they have a big excursion, but I don't know the precise value - anyway, below 50 mV should be safe".
     
    Last edited: Dec 21, 2017
  6. Friscosfoe



    Well I’m getting my Gumby back this afternoon, but because they turned it around so quickly, it might be they found no problem although I asked to check for a dc offset. I’ll report in.

    May need instructions on operating a voltmeter.
     
  7. Don Quichotte
    Have you told them about measuring while the music is playing? Of course they should be well aware this is the only way you could measure anything at the dac's outputs, but still...

    I'll tell you about the voltmeter in a few hours, right now I'm a bit in a hurry.
     
  8. Friscosfoe
    Got the Gumby back. They confirmed problem and replaced a “mod. “ It works and sound great. Still would like to test the outputs.
     
  9. Don Quichotte
    And what could this "mod" be? Maybe one of those small, unannounced changes / upgrades Mr. Moffat has recently admitted they are making from time to time?!

    Now the big question is this: does your Gumby sound any different now, apart from the lack of static and popping sound? (I mean in terms of detail, tonality etc.) I'm asking because I've had some matching problems with the rest of my gear in terms of timbre and tonality and I'm wondering if this problem had anything to do with it.

    As for the Dc offset measurement, the procedure goes like this:
    1. First you need a multimeter. Even a cheap one will do.
    2. Play any piece of music through your Gumby. It doesn't matter what, but it's essential that the outputs are "live" when you conduct the measurement, not shorted or disconnected or whatever those relays are doing when there's no signal entering the dac. I think (I'm not trained in electronics, just an amateur) that it's better if the dac has been warmed up (for a few minutes / tens of minutes, not necessarily days).
    3. Turn the multimeter on and set it to measure DC voltage, for instance set it for up to 20 V at first and then you can use other, lower scales. In this picture, for example, the DC voltage scales are in the higher left quadrant, below the "hold" button.
    4. Insert one of the multimeter lead tips into the center hole (signal) of one channel's RCA output connector, making sure you touch the metal inside, and touch the other lead tip to the outer jacket (ground) of the same RCA connector. Write down the value shown by the multimeter and then repeat the procedure for the other channel. Alternatively, it might be easier for you if you conduct the measurement at the free end of an interconnect cable
    connected to the RCA outputs. As long as the cable is functioning properly, it doesn't influence the reading.

    Apologies if I'm too much into stating the obvious in the above paragraph, I mean no offense - I just have no idea what is your level of knowledge.
     
  10. Friscosfoe
    1.maybe mod refers to a module of some sort
    2. My level of knowledge on volt meters is zero, thanks for the help.
    3. Getting to the main point, I was thinking last night that the setup sounded better after the repair. More detail in strings and percussion, and somehow more vibrant and exiciting. That’s subjective I know, and maybe it’s by comparison to the dc-1 that I’ve been using. Still the dc-1 is a solid dac with good detail, that I would say is competitive with bimby , but the repaired Gumby is aways ahead of the other two.
     
  11. Don Quichotte
    Thanks! Fingers crossed mine will sound better too (especially that your impressions refer to a not fully warmed up Gumby). Looking forward to read about your DC offset values now.

    Anyone else willing to try and measure it?
     
  12. Allanmarcus
    Hi. Bimby owner here and I just got a Gumby (gen 2) a week ago. My son, also a headphone audiophile, is visiting and we set up the Mac to output two USB ports at the same time (with drift correction), and set up a well made RCA switchbox with RCA cables running from both DACs into my Black Widow 2. We tried lots of headphones and for the most part cannot tell the difference between the DACs. I think, maybe, I can hear a difference in some female vocals. To me, the bimby might sound a tad smoother on some Female vocals.

    I guess I was hoping for larger difference between the DACs, but maybe we are just listening for the wrong stuff, or to the wrong stuff. I supppose if I cannot hear a difference, I can sell the Gumby and save a lot of money.

    Any suggestions on how to better understand the value of the gumby over the bimby? We also tried the MJ2 with LSST tubes, and will try with WE396a tubes tomorrow. We figured SS would be less forgiving with DACs, but maybe not.

    Oh, I did try the Gumby balanced into the MJ2. Of course it was louder, but that is to be expected.

    Thanks
     
  13. Ojisan
    I don't have experience with bimby but at one point I was comparing Jot's AKM 4490, Gumby, and Yggy. I recall that Gumby presented a very unique bass and mid-bass fullness not heard in other DACs. You might want to pick some tracks that would expose that area. For me, they were large orchestral pieces, larger ensemble jazz, and some country music.

    Other areas where I heard obvious differences were the trebles on tracks with a lot of left-right panning with sound effects and cymbals. They often reveal treble timbre, soundstage, and extension.

    Not sure if that helps... sounds like a fun experiment though :)
     
    sheldaze likes this.
  14. sheldaze
    I'll second the above, with regards to bass and mid-bass. It was a fullness I heard from Gumby, and in my speaker system more of a three-dimensional presence and impact from the Gumby versus the Bimby. I am still trying to learn more about what causes the audible effects. My guess, today, is the power supply (Bimby-Gumby-Yggy) first upgrade allows for a little more impact and depth, second upgrade allows for a more tightly defined, more resolving and cohesive bass in Yggy.

    On headphones, it is not quite as audible. I'll have to do some experiments with my BW2. Last DAC comparison opportunity with Gumby (when available) was through Glass, which conveniently has two inputs. But I too have a transparent RCA switch-box. So next time...
     
    RCBinTN likes this.
  15. Ableza
    AND... since all audio is subjective, if you don't hear a difference then you don't hear a difference and there is nothing wrong with that. Sell the Gungnir and enjoy the music!
     
    Last edited: Jun 27, 2018
    GrussGott, Baldr, sheldaze and 3 others like this.

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