Discussion in 'Digital: DACs, USB converters, decrapifiers' started by Scott Kramer, Nov 8, 2016.
Is that a custom title? Both Scott and landroni has it.
Scott was the first person I saw with it and I assumed he was the only one due to his epic I2S haxx0r5 skillz
Used to be "Almost Made". Kinda like this current status though
Ah you as well Friday. You are in a good company.
FYI: Here's a detailed pic of case closed up and functionality coming together... hope you guys like how I did it.
Optical/Coax is unaffected* just select it like normal… but when you select USB, you get i2s…. and, you can even put jumpers on to return normal USB operation (like stock). Except: you can always select USB, even when disconnected this lets the i2s tap work, normally it just toggles optical/coax.
*There are 2 completely independent i2s paths into different channels on the DSP (the MM super burrito filter)
Looks great! Did you ever solve the sample rate issue? It's unreal that you've made this mod that can virtually return to stock with just a few jumpers. How long have you spent working on this? Seems like a fun time sink.
Impressive! Those mediocre CMedia USB interfaces are holding back Schiit DACs.
Thanks! Exploring the sample rate issue a bit... but on getting there, it's interesting how schiit's utilizing the usb CM6631, at a bare minimum it requires only a 12MHz ext clock then uses it's internal PLL (this derives all other required clocks). On chip PLL's as far as I've seen, always have a spec'd jitter no matter what the input, 50ps+ (at best), 200ps etc... no spec on this from its datasheet that I have though.
However, schiit's using optional external 45/49Mhz (x44.1/x48 multiple) clocks. This suggests it needs these clocks to perform better or at *least* up to schiit's standards... hence can't just use the internal PLL and call it a day. Youtube the phase "phase locked loop" a bit, once you see the scope animations and theory, it makes sense how this adds jitter.
So, not being capped by internal PLL performance, it may be *really* sensitive to USB source!
...buuuut lol this usb chip is still a piece of work... you have this huge chip (basically an SOC on its own), a flash chip, three clocks etc. to unravel packetized usb, extract spdif, then unravel i2s, and clock it, wowzers!
I bring up the ext. usb clocks because:
The AK4113 chip coax/optical in... here they are using it at it's bare minimum, no ext. clocks, and reliance on the internal PLL, even the bimbo* uses it this way. The gun/Yggdrasil uses this same chip but with ext (x44.1/x48) clocks, in addition they are using voltage controlled clocks to really zero in and tune them when the source is good!
BTW there are 2 independent i2s paths to the the (burrito filter) Sharc DSP... CM6631-i2s and AK4113-i2s
Apologies if a bit *TMI*, ...interesting that there may be a spdif capped performance limit here.
i2s direct bypasses all this happy horseshit -- seriously though, fun and learning-- practice for possible optional i2s in on a Yggdrasil
Measuring the required 12Mhz (U22) clock:
The optional 45Mhz (Y1) (not pictured, the 49Mhz (Y2) is there and measures perfectly also)
Hey Scott Kramer! Thanks for all the hard work here! Sent you a private message not sure you got it. I'm new here so may have sent it wrong.
You have run I2S from your Squeezebox Touch (I still have one), a Kali reclocker, and a Raspberry Pi dac I believe. What there any appreciable difference sound wise between these setups? I would think the Kali to the Modi Multibit potentially would have the best sound theoretically. I am tempted to go this route and mod my Modi Multibit for I2S.
I'm currently running a HP beast of a computer (server) USB out to Modi Multibit. Would be nice to downsize and gain better sound.
Thanks for all your help.
We - crazy tech guys!
Thanks! Yeah kali/moby is pretty impressive so far!
I'll try to do something quick on the squeezebox touch i2s out, did record video doing it but needs editing & a voiceover. It has transformer decoupled BNC also.
Maybe you should at least get started in the pi ecosystem, with a pi3/picoreplayer or moode or raw 384K linux w/usb ( I use a piZERO to keep it minimalist and no extra features adding noise ) Great thing is, get a few pi's and test things in parallel, use the best to listen to!
Then graduate to a hifiberry digi+ pro, a kali/piano 2.1 hat dac, compile the 384K linux, etc, etc. Get a flexible 5V/3.3V LPS -- best to learn and build on it!
I'm gonna leave it there... some work and reading you can do to get to this point! It's evolving & interesting place to be
Some Moby i2s experimentation—
Was visiting friends this weekend... we set up a few different speakers and optimized some things. It was like pulling teeth getting an Anthem AVM50 processor to not use it's built in DSP/DAC/Crossover etc.
Eventually got it correct and the Sub integrated. By then ~11PM could really hear the differences in Dac's. The amp (MCA50) seemed to stay transparent through everything.
Had a few Dacs to test: Anthem built in, psaudio, pi/kali/piano, moby spdif, moby i2s, hifiberry D+PRO.
The moby i2s was our favorite by the end. We were A/B'ing by complete song. Width and height and Z of the sound stage changed, along with more complexity in everything... this is the Dac we were completing songs with, it held interest. Also the Energy Veritas 2.2i's were just bigger sounding than the ELAC UB5's, more enjoyable in that room.
The moby spdiff in though sort of normalized it with the other Dac's -- just was not as good. Still need more testing on that, only used a hifiberry digi+ PRO & no Linear power for it, it really needs it because there's no onboard regulators or ground filtering. By that time we were just enjoying music, done with testing.
*** warning unedited, unlisted clip, just us chatting-- but can see one of the environments w/moby i2s ***
Turned on the camera for a bit -- it's me behind the camera. Around 1:00 is a closeup of the Anthem gear and Moby is2 <--> pi2design prototype (running piCorePlayer 3.11 audio build)
Really wish I turned the camera on again after the system was singing & the moby (and our comments on it)... it was so different from starting earlier!
Thanks for the update Scott Kramer! So you are running the Modi Multibit I2S out from the Kali reclocker or from the digital side of Micheal Kelly's 502 dac board? I had an order in for a Hifiberry digi+pro, but it was out of stock and I cancelled the order. Was going to get a 503SPD2 from Michael Kelly, but I see it is not going to be made after all - quote below. Bummer!
I think I am going to order a Kali reclocker, since from your listening session, this had the best sound. Since you have run it both ways, what do you prefer? Kali or pi2design to Modi Multibit? Since the 503SPD2 is not being made it seems counterproductive to use the 502 dac for just the digital side.
Time to go all in and mod the Modi Multibit for I2S. I have upgraded caps on my preamp and speakers and have built and modded dacs in the past and this looks like an easy mod, although I will need steady hands soldering.
Question, did you have to up the sample rate in software for the Modi Multibit to work with I2S?
It is my understanding that Schiit dac sound signature has to do with their burrito filter ( think that's the name), and when you upsample to 24/96 or above you are no longer going through the burrito filter. That is my only concern.
Thanks again for all the testing, listening and hard work.
It's a good time to be a crazy audiophile!
Most listening so far has been from the 502 board exclusively (if i2s) for its reliable connection, but the kali is my favorite when taking the time to hook it up carefully. Just started today pondering the best way to hook it up reliably, hooked it up and listened all day today with it like this in the pic. (set to 88.2/24 upsampling (2x 44.1)) It really sounds wonderful, I'm used to it hooked up optically (from mac) if at my desk. More ambiance on jot/hd650
It is a bummer Michael dropped the SPD2... only option there is the 502DAC, but it's surprisingly good. Once I get a solid connection for the kali I'll do more listening for the best. There is a kali2 in the works (I'm even emailing back & forth with the designer, connection options & some other things)
176.4/24 192/24 is where the burrito filter's not used.
Have a big post coming about the sample rates... sit tight hint: grab a Digi+ PRO
This is just a bit of a documentation post.
Getting the kali set up good with dedicated power (LT3042) and the piZERO with separate power. Making sure everything works so I can start thinking about how to come up with a nice connection... and an enclosure. (also keeping the gummy/Yggdrasil layout in mind)
Anyway it sounds really good! Having fun comparing it to an interesting new allo hat dac, normal pi/spdif and optical.
I post some pic's of that dac, look at the analog side cap, supercap, dedicated reg's/filters for digital/analog (LT3042)/and even clocks) -- it's a prototype, and just set it up, it's not messing around sound wise
Interesting, the faster 45/49 MHz kali works at 44.1/48 -- thought I tried that before!
It's coming down to the DSP expecting specific SR/Fs/MHz combinations...
I already did because they're cheap and easy to get - and really enjoying how well it works with the somewhat humble SPDIF in the Modi Multibit, money well spent- it sounds nice. High percussion has different timbres again, and cuts through the mix without all that swampiness.
If you've managed to do something insane with it, to bypassing the SPDIF and squeezing even more out, then tell all
This has been haunting me since I first saw it. I've been driven to extremes by every input from my PC to my Bifrost Multibit sucking so bad. I can't even leave the USB plugged in because it infects the other inputs with the noise it picks up. :/
I'm building an RPi transport, got a Digi+Pro on the way and will get a 502DAC, but I want to give this a shot too. I figure worst case I'd wreck a $75 USB board that's useless to me anyway. I doubt I'd have the balls to hack on a $250 DAC. LOL
So, any ideas where to start? I'm not cool enough to have an oscope, but I'm down for some risky soldering heroics. I don't see a convenient 8-pin resistor like in the video. I imagine I'll have to desolder some of the legs of the USB chip, lift them up and jumper them on the back panel?
Working on it, no need to hack up that perfect board, especially when there are beautiful headers underneath that its plugged in to.
Headers you say. These maybe?
I was all excited then actually looked at it and they're downstream of the input selector. I take it it's more complicated than just tracing the leads back with a USB board in.
I'm talking about the pin headers right under the usb board. Perfect place to go in with the i2s and also to set logic telling it USB is present. Those in the pic are i2s test points after what looks like a buffer chip (I've known about those, as you can see them in internal pics on Schiit's site). Probably can't tap directly into them as the other inputs interfere... there will be logic involved, i2s wires would be too long, and possible impedance mismatching. I like to carefully go backwards with a scope to make sure it's correct and do lots of testing. If you have the tools to do it, try it out!
Gum's & Yggdrasil's are scarce these days or I'd probably have something going by now! Hoping there will be *more* hints or an actual upgrade to the Dacs soon, so we see the direction they're going. So far it's the MP, a possible USB/SPDIF isolator (separate or combined with the MP), or Bifrost update.
Feels like somethings brewing with everything out of stock like it is.
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