Modi Multibit: Multibit for the masses.

Did a null test sending data out through the USB XMOS driver to a Gustard U12 DDC to SPDIF, and looped back to an RME Fireface UC SPDIF input then back through the RME USB driver. The DAW is able to send and receive data simultaneously. Used a start and stop pulse for data alignment. Data was 44 KHz 24 bit stereo pink noise, channel decorrelated. Then subtract all samples levels received from all samples sent. Results: not one single sample level out of place. Not one single bit error in 67,737,552 bits sent and received. I'll do a more complete write up including presentation of measurements a little later when I get rid of sinus headache.

Please note that correct sample levels only implies all data sent was received correctly. It does not describe the timing of data presentation to the DAC (jitter). That is another story as is separation of digital from analog power / ground; noise imparted on the analog signal by the digital signal in the DAC.

 

ColtMrFire gave me a good idea, so I will hook up my modi multibit with the Fiio x3 via coax and see if there's any difference compared to my win10/bughead player via USB.can't wait to get home!

 

Here is the short version of USB -> SPDIF -> loopback -> SPDIF -> USB data stream accuracy.
Track 1 is source data sent
Track 2 is loopback received data
Track 3 is track 2 subtracted from track 1, the difference



Here is a very high y axis zoom on track 3, the difference. Not one sample difference.

 

@atomicbob will you measure a similarly-priced D/S DAC, just for fun?

 

I have some plans in the future for that, yes. Just need to find time.

 

This is truly awesome work.

So bits are, after all, just bits even in the usb audio stream domain. The only remaining sources of problems would be timing (jitter) and electrical noise. So, SPIDF is nice from the standpoint of being electrically noise free, leaving just the jitter for SPDIF - if the SPDIF converter is really good (low jitter) this would make sense as having potential to be the best digital audio solution.

Edit: I realize I am essentially repeating @atomicbob's conclusions from above, but they bear repeating.

 

Optical in SPDIF is guaranteed free of electrical noise, but not Coax. While the spec requires Coax connections to have galvanic isolation, not all manufacturers do so. And even then, only Optical guarantees complete isolation from electrical noise coming from the source. For the latter, the remaining issue is indeed timing accuracy (i.e. jitter).

 

Hi folks,

I understand that a couple of comparisons have been made between Bifrost Multibit and Modi Multibit, mostly on headphones. The consensus seems to be that the difference in sound is marginal. I have a high-powered two-channel setup, and will run digital out from a Music Hall CDP. I've now got an Aragon 8008BB to punch up the difficult-to-drive Vandersteen 2CEs. Is the power supply regulation of the Bifrost Multibit a consideration, or is the Modi Multibit enough to get me the kind of transparent sound I'm looking for? Or should I be thinking Gungnir territory to do this system justice?

Many thanks,

Paul

 

That's really more of an all purpose advice thread question, but I would say go for the Gungnir Multibit.

 

@AllanMarcus-William Burroughs

If I'm right, I take payment in dislikes

 

Oppenheimer - No payment/points necessary.

(Although William S. Burroughs went to school in (or near) Los Alamos for a while.)

 

So, the bomb, and bombed.

 

Does this mean USB to spdif conversion gives the cleanest sound? Not the first time I've heard this.

What converter is everyone using ?

 

Unless I'm misinterpreting the test, all it tells you is that the bit-level data is transmitted correctly. It tells you nothing about noise and it's affect on the analog electronics nor does it speak to levels of timing error/jitter (at lest below individual bit-width level and that would be a HUGE amount of jitter - to the point where you couldn't maintain a signal lock).

So, in essence, what it says is there's no bit-level corruption going from USB to S/PDIF and back again - and I don't think it says anymore than that, but I stand to be corrected.

 

That jives with my understanding, but I think the broader picture is that the differences heard with digital is NOT due to dropped packets or any other data corruption. It is, as you say, something to do with jitter or the effect of noise on analog components.

 

http://www.head-fi.org/t/817404/modi-mb-technical-measurements#post_12793785

The inferred jitter is measurably lower with USB to spdif conversion here vs USB alone or spdif alone... looked at that and then these measurements posted here and seems like it's jitter/error free with USB to spdif conversion.

 

Is anyone having dropouts with their Moby? I'm having to reset it very often because I can't stand the audio getting glitchy and dropping momentarily every 10 seconds. I'm using straight USB from my rMBP 2015.

 

Not ever, no, it's really well-behaved. I use it TOSlink from my desktop PC, and USB from my mobile devices, and its behaviour has been impeccable. Before you start considering stuff like a USB decrapifier, do you have some other devices that you can hook up to it via USB, just to check that the DAC can behave itself? Also, and this sounds stupid and basic, but have you tried a completely different USB lead, in case yours is marginal?

Do these basic checks before fretting, or considering stuff that will cost you money - and sorry if I'm teaching you to suck eggs!

 

I've noticed some probs with mine (on Windows 10) that don't seem to affect my other DACs. I have drop outs every once in a while, usually they are few and far between though. It also glitches out sometimes when I'm playing a game and listening to music at the same time. Using SPDIF instead of USB seems to alleviate these problems.

 

Any comparisons between modi multibit and bifrost multibit? I'd like to understand whether it's worth upgrading my bifrost or getting this to replace my bifrost 4490.