USB-DAC Prototype

Just some pics of what we built yesterday...



That's my old instant saver card behind it... same size as a credit card!



Unlike cheap "root vegetable" USB DACs, this one's actually got a proper buffer for the optical transmitter, which is 3x over rated!

Actually, one we took a peek inside of, had no buffer at all and was trying to drive a 15mA optical transmitter with 4mA output current. But instead of concentrating on getting the job right they blame a chip's specs and the following of easy believers collect their pitchforks and torches and join in the blame game not having a clue what they're talking about... shades of HD250? Talk about throwing baby out with the bathwater...

Ours also has another buffer (again 3x over rated) which drives the isolating 75 Ohm matching transformer for the coax (S/PDIF) output. Will it drive a long cable? Well that's what transformers are good at!

It's also got an output stage... yes AN OUTPUT STAGE! Which drives headphones direct - any impedance - with only 18 Ohms output impedance. It does not go direct from the DAC outs without any filtering like most do! The output has a thing called gain and it also has proper sampling frequency filtering that's effective and yes it's fast (some people call it PRAT but I call it fast) . It also does line level, and there is a 3 position switch hidden away under the USB socket to let you preset the volume to suit - and you can press it to mute - and press it again to un-mute... snazzy!

(we'll probably get hauled over the coals for it being small and hidden by the same people who love awkward and fiddly gadgets on cellphones, cameras etc...)

It also sounds like a Reflex M... either direct to headphones, via optical or coax into "the big DAC", or via the 3.5 jack line out direct into a pair of Proprius.

It will not have a vinyl sticker on it printed with a load of absolute b*ll*cks... people buy such things and then wonder why they've no money left to buy anything good!

We've now got to tighten the mechanical tolerances and get the thing into production.



Edited by Graham Slee - 22 Nov 2012 at 2:29am

Graham, it is looking very good and I'm sure it sounds very good too. That would be a very handy device for my PC at home or at work so I will eagerly await more news.

franklin wrote: It is nice. I guess it is powered by the USB?

Yes, USB powered, and also within the USB rules of 100mA load current, and capacitive charge limits.

One use is where a PC is one of your digital audio sources but far from the high fidelity system DAC. A fibre-optic link is quite handy in such circumstances, and this USB-DAC will drive the optical cable required.

This was the last thing we tested last night and I'm using it that way as I type. I'm quite impressed by the clarity, and I suppose I'm also "advertising" the quality of the "big DAC" prototype by saying so.

Getting the same results using the coaxial link.

But the one I really like is its main use - as a DAC, providing analogue outputs. I think we need to supply some velcro coins so it can be "stuck" to the PC or laptop. It is then a fantastic USB headphone amp or a beautifully sounding line-out source. I've been using it just like that in its "breadboard" state for months.

From the pictures you will see we've used conventional "wire through hole" components as well as three surface mount components. The reason? These, like all our products are going to be hand made by real human engineers - not machines. Also, we know our components - we know which components deliver our musical and spatial sound, and they're simply not available as surface mount.

OK, I hear you. Unfortunately people seem to have different ways of listening, some with their ears, some with their eyes and some with their wallets. I presume to be in the 10 and try to convince others to listen and hear, without concern for HiFi Journo's ratings, superfluous features and the inevitable "Ah, but XYX's DAC/Phono/Amp COSTS more, so must be better"! A supposition perpetuated by many dealers and indeed on other forums.
We just need to keep spreading the word; The Truth will out.
Meanwhile, the USB-DAC is looking really impressive in terms of useful features and with your house sound guaranteed is already on my shopping list.In fact I like it so much, I should like to be first on the order list.