My new-favorite blog (other than this one), Digital Audio Blog, turned me on to a unknown (to me) USB-to-S/PDIF converter from Human Audio, the Tabla. Yes, I’m shameless, but this converter is really interesting. While it’s yet-another-converter, sure, and yes, I hear you when you
rant say that an off-board converter is a theoretically abhorrent band-aid that serves only to prop up support so-called legacy (that is, “not computer audio ready”) DACs that ought to be put out to pasture. To this, I say: we all just need to get over ourselves and realize that while theory is one thing, reality has some practicalities that are simply impossible to overlook.
Like my obsession about how crappy computer-sourced power really is. I have absolutely no good reason for this belief — other than deductive reasoning based on anecdotal evidence and a smattering of non-rigorous personal experience. It is my (deeply considered) opinion that the power leads coming off of a computer can muck about (yes, “muck about” is a technical term) with the signal as received by the DAC. I fear that this mucking-about happens way prior to the DAC chipset, and that the damage may well be done before the data leaves the receiving USB chips to wend their way toward analog conversion. So, somewhere between the source and the receiver, there lies a dragon. To defeat it, we need to kill the power.
Unfortunately, many USB DAC makers use chipsets that require a live power feed in order to work. That is, even if they then use their own first-rate power supply to run the rest of the DAC, the first step into their state-of-the-art DAC is filled with computer-based power-munge.
Power munge. I like that.
Ideally, the USB receiver would need no power at all — like my current reference, the unmatched (in my experience) Legato from Analog Research Technologies. With that converter I use a USB cable that actually has no power leg at all. And yes, it’s spooky-good.
Anyway, if this power-less cable approach isn’t viable due to the design of the DAC, a good USB cable ought to help. Especially one that sends the power leg out over a separate path, isolated from the signal leg. Wireworld does this. Ridge Street and Acoustic Revive take that a step farther and actually send that power out a separate cable entirely, a solution I’m totally on board with.
But I digress. Getting back on track ….
Converting the heathens
The next step in the audio chain up from the computer-source is the DAC. Some DAC designers, like the folks over at Berkeley Audio Design, have said publicly that they’d rather put a bullet into their DAC than a USB interface (I’m paraphrasing). While a bit extreme, the thinking is that you simply can’t get the two to play as nice as you’d want — the computer is just critically, irrecoverably, corrupt as a source. An off-board “buffer”, then, is the only way to go.
Leaving aside the polemics, this does allow for a lot of interesting rack layout choices. Personally, I think my rig sounds best when my computer is not sitting on top of (or right next to) my DAC — so being able to separate the components out is actually helpful. Perhaps it’s EMF that’s to blame … but that’s an issue I’ll address at some point with some nice EMF-blocking shelves from Audiav, I think. Stay tuned on that score.
Finally! Some Details
Okay, all of this is one horribly circuitous lead-in to the battery powered Tabla from Human Audio. Given that power is a concern, many clever folks have started to wonder if we can simply eliminate the power company entirely from the equation. Red Wine Audio comes to mind here. Apparently, Human Audio is a like-minded company.
The Tabla uses Lithium-Iron-Phosphate (LiFeSO4) cells to drive the guts of the converter. This is top-notch battery tech. One of the discussions over at Computer Audiophile that came up with the M2Tech EVO, a converter that I had in here myself, was whether or not that unit would benefit as much as M2Tech’s other converter, the HiFace, as modder JKeny found. In researching how to do that, that is, mod the EVO with a DIY battery supply, I realized that I’m not a modder, not terrifically DIY-inclined, and became quickly convinced that were I to pursue this particular approach, I might well have my entire audio rack slip into an artificial black hole the moment I powered it up. Okay, maybe not, but battery management is a PITA and very hard to do with a DIY set of parts. This is why the Red Wine Black Lightning off-board battery pack sells for $1k — solving the charging/recharging thing elegantly is significantly more difficult than I had anticipated. Which is why the Tabla is interesting — this is all done for you, and for about the same price as a Black Lightning pack by itself.
The unit is fully 24bit/192kHz compatible.
It’s also driven via driver which they’ve sourced from M2Tech. While I find this suboptimal — I’ve never not had driver issues with M2Tech — others tell me that I’m a whiny baby and that I must have been smoking crack because they’ve had no issues whatever. To which I say, quite naturally, “suck it”. But I digress….
Connections are BNC (vastly to be preferred) and RCA (for losers).
6moons appears to be in the middle of a write up, so check back when Srajan finally gets around to finishing it.
* Get over it — it’s my blog and I’ll be as idiosyncratic as I feel like being.