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Schiit Bifrost Multibit A/B Test Video

Discussion in 'Sound Science' started by watchnerd, Jan 20, 2016.
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  1. watchnerd
    And here is some more detail on the differences, as well as compare and contrast with the other models:
    "To expand on the comment about discrete stages:

    1. The discrete stage in the Yggdrasil and GMB are both just buffers. The DACs used there have voltage output. So, they are very simple stages, just four active devices per channel. However, as measurements clearly show, this simplicity does not compromise distortion performance (this is usually the penalty paid...simple discrete amps typically have high THD.) That's why when you see some "2-PPM wonder amp" it usually has about 80 active devices per channel. We can argue till the cows come home which sounds better.

    2. The discrete stage in the standard Bifrost and Gungnir is actually a small amp stage—not exactly a discrete op-amp, due to its very specific gain structure and open-loop bandwidth beyond the audio band--but it also takes a voltage output of the DAC, amplifies it a bit, and passes it on. No I/V necessary.

    3. Bifrost Multibit is totally different. Its DAC has current output, so it doesn't just need a buffer--it needs an actual I/V stage, or current-to-voltage converter stage. There are many ways to do this, from op-amps to discrete. If you're going discrete, it's best not to use a typical voltage-in amp topology, but to design specifically for current input (into, say, the emitters, with overall feedback to bring the input impedance down--you want very LOW input impedance in an I/V stage, unlike a voltage amp.) However, Bifrost Multibit doesn't have a lot of real estate on the analog board, so we had to choose: discrete I/V OR burrito filter. Both wouldn't fit. I believe Mike and Dave made the best choice, which was to retain the burrito and lose the discrete I/V.

    Consider this: the discrete I/V I did for Theta's Gen V had 250-ish through-hole parts...on a 4 x 6" teflon board...per balanced channel. The complete Bifrost analog output stage--which includes digital filter, DAC, glue logic, local power supplies, voltage references, and the I/V stage is 4 x 5". Surface mount gets us only so far."
  2. Noodlz
    it bugs me that he's doing this test with such a terrible usb / source setup. My hunch is that because the source is so bad, theres no way you'd be able to tell much of a difference between the DACs. People underestimate how important the USB chain is. Computers are noisy as hell. add that dirty variable power to a bad cable wit ferrit chokes, by the time the signal gets to the D/A converter its like scrambled eggs....
    i think if the tests were done either with usb that has a split for the power (like the ifi USB), or at the very least not a piece of crap USB cable, he would have heard more of a difference.
    pavement714 likes this.
  3. cjl
    USB cables either work or they don't. Unless you have some reason to believe that the cable was so bad that the DAC was actually receiving the wrong bits, the cable didn't make any difference at all. Similarly, any computer should be as good as any other, as long as it can maintain the proper data rate. If you have an ancient computer that is so slow that it keeps dropping out, by all means, you should improve it, but if the computer can supply data at the desired rate, you don't really need to worry any more. Power supply noise from the computer should be rejected by the DAC, especially in the case of something like the Bifrost, which has its own power supply.
    Vkamicht, watchnerd and chaos215bar2 like this.
  4. watchnerd
    What electrical phenomenon would this better cable improve if he's not getting digital dropouts or bad-grounding-loop induced hum?
  5. castleofargh Contributor

    I read that kind of stuff all the time, but in practice the only time I get 2 devices to sound the same is when they perform similarly. on a super crappy and noisy USB it would be a lot easier to figure out an audible difference from different designs between 2 DACs.
     what you're saying is the very opposite of what I would expect to happen in reality. I would expect even some cheap stuff to sound very fine when fed an ideal power and ideal signal.
    on a side note his test is better than basic sighted evaluation because it allows for rather rapid switching, but I wouldn't take his conclusion at face value. it's still a mess of a test, I'm doing more rigorous tests, and most of them I wouldn't even talk about on headfi because I find them full of holes, so make a video of it... ^_^.
  6. Noodlz
    i'd rather not get into the sciences / pseudo sciences that i dont have definitive knowledge of. (Dont wanna be one of those that start a flame war where everyone argues these things).
    It's just my personal experience / observations with gear that when using sub-par usb cables, the sound quality is definitely worse to my ears and to the musicians ive worked with. That and in recent years when i started using the USB-DDC devices i discovered they improved the sound drastically, for me and people i blind tested them with (purely out of curiousity as part of this hobby).
    To my ears, crappy interconnect / sources (digital or otherwise) on good gear tends to bottleneck to performance between them. My observation is that good gear is revealing, and if you have a crappy source, then what is revealed between the two would be similarly crappy~
    It just bugs me when someone states that theres no audible difference between gear, with a setup that is less than ideal, it tends to get people take the results binarily and get evangelical that all non-budget gear is snake oil etc etc..which makes other people doubt & miss out on the good stuff. (i've had friends like this, until they heard my setup... lol)
    I'm definitely not qualified to post video test findings / explaining things tho. not my realm of expertise. Can only share my experiences / thinking. Would be nice if someone at some point did some proper tests and made sense of it all =P 
    Just my 2c. YMMV
  7. Joe Bloggs Contributor

    How did you switch between the regular cable and the USB-DDC devices? How did you shield the difference in connection noises and your act of connecting the different parts from the subject? Did you check for different latencies and levels in the device receiving the two different inputs? How many trials did you run? How many came out positive? You do know that blind guessing had 50% chance of being right on average and possibilities of much higher hit rates than 50% on a small set of trials, don't you?

    I find it deeply disturbing when people throw the term "blind test" around so casually and say "we did it, we passed it" on test topics that simply shouldn't get a pass. It started with Rob (from what I see) and now I'm seeing it more (or have my eyes just been opened to it?). It could spell the final nail in the coffin for scientific progress in audio technology--I'd rather people not advocate double-blind tests as a method to distinguish audible differences in gear anymore than for everyone and his mom to claim positive DBT results for different USB cables, a 16/44.1 track and the same track upsampled to 24/192, you name it... :ph34r:
  8. Noodlz
    @Joe Bloggs ah the tests were done fairly casually. As to your questions i'm assuming they're rhetorical? I've been out of the hard sciences for more than a decade now, so my lab / experiment etiquette is probably pretty lacking~ =P
    That being said i tried my best to not introduce too many biases / etc...and those are just my personal findings. I am in no way claiming that USB DDC is definitely superior than direct USB through my casual tests~ 
  9. spruce music

    Being casual is unfortunately going to lead to unreliable results. 
    I have taken various USB devices and played hires music.  Changed the USB cable or installed hubs etc.  Played the music again.  Recorded both times.  Subtract one from the other and what is left is what is different.  What is left? Pretty nearly nothing.  Nothing to explain a sound quality difference. 
    So my conclusion if I think I heard a change is I must be fooling myself because the difference isn't in the signal.
    ArchieFunker likes this.
  10. Peter Hyatt
    any opinions on Bifrost v Bifrost multi-dac sound difference from members here?  
    I will be a new Bifrost owner shortly, and didn't order multi-bit but I can always upgrade down the road.  
    I don't understand the difference.  
  11. theveterans
    I went for the multibit since multibit DACs are generally warm sounding. Schiit Bifrost Multibit is known to be warm and musical which pairs well with my K712 headphones. Another reason is that the multibit version uses the Analog devices DAC and I used to have an old Pentium 3 PC with Analog Devices (soundmax) DAC which sounded excellent to me.  In terms of resolution, it's subjective, but both Bifrost 4490 and the multi-bit sound excellent at their price point.
  12. gregorio
    Huh, no it's not. Resolution is objective, it can easily be measured. In fact, "resolution" is a measurement!
    Ah, so it changes the waveforms rather than reproduces them accurately, good to know. Definitely a DAC I'd avoid then!
    muza_1 and chaos215bar2 like this.
  13. milosingh


    I don't want a warm DAC either. Tube amps are welcome though. :p
  14. watchnerd
    So in the 1990s multibit digital sounded harsh and unnatural (according to many in the audiophile press), but in 2016 that same multibit tech now sounds warm?
  15. theveterans

    Times change IMO. Well, Schiit Multibits including the ultra resolving Yggdrasil doesn't sound harsh but more natural and organic. I guess it's due to new filter implementations, more reliable ladder resistors, etc.
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