Digital to digital....?

[tfarney]

Well, I can't pretend to understand all of that, but I knew zeros and ones had to be converted to voltage somehow, somewhere. Yeah, give it a bit more time. Lots of people, myself included, find themselves turning down the treble a bit at first, then gradually bringing it back up to flat.

 

I haven't tried it in a nearfield config yet. If it doesn't work there, I have options.

 

Tim

 

[tfarney]

My solution arrived yesterday. It is a Trends UD-10. I believe I already posted the description and specs. It reads well. How does it sound? Well, first, two caveats:

 

1) I'm not yet using it as a USB to whatever transporter to my Panasonic. I currently have it in line from my iBook to my headphone amp, using its Burr-Brown DAC as an external soundcard/DAC

 

2) My Senns are pretty capable when it comes to listening in, but my amp, a refurbished 70s Harman Kardon integrated, while it has pretty respectable specs (actually as good as/better than all but the more expensive modern tube amps, FWIW) and has been recently serviced and brought up to speed, probably isn't resolving enough to reveal the really small stuff

 

How does it sound? Good! I'm not exactly sure what to attribute to the Transporter/DAC vs. just getting the last bit of audio processing out of the Mac's environment, but good. It was already quiet, but the Trends certainly hasn't added any noise. I have plugged my Etymotic ER6s directly into the trends and opened up the volume in iTunes (the Trends has no volume control). No hiss, no hum. Nothing. My hearing is probably not the best, bu in any case there is nothing you'd ever hear with music playing, or even pick up in the little space between tracks.

 

I've also listened to lossless files of really good recordings through the Trends, into the HK and then to the Senns. What is different? There seems to be a bit more clarity than I had from a simple line out. And the soundstage seems to have opened up (I hesitate to use that word when talking about phones, but there is a sense of space and depth, though it's around your head, not laid out in front of you) .

 

It's all pretty subtle and I could be hearing what I think I'm supposed to hear. I am sure of what I'm not hearing though - which is noise, distortion or any degradation of SQ that is audible within the limits of my equipment.

 

I'd say for a transporter with a built-in clock and DAC and USB in with 2 coax, 1 digital, 1 optical and 1 digital balanced out, for $140 bucks, they did pretty well. If you need something like this, it's almost worth giving it a shot. I'm considering getting a better DAC or two in here. If I do, I'll report back on what I hear.

 

Those crazy Chinese...

 

Tim

 

[The Computer Audiophile]

Very cool Tim. Thanks a lot for the report!

 

[davip]

Hi Tim,

 

You seem to want what I'm looking for (ref: http://www.computeraudiophile.com/node/452) -- a digital PWM amp with a USB input. I think what most people on this thread weren't getting was the 'powerdac' aspect of all this, where a digital signal is amplified digitally and only converted to analogue at the speaker terminals. For all those with digital signals (i.e., CDs, Wav files etc.) this is surely the ideal, as amplification without conversion ought to be free of quality issues [and cable voodoo ;-)] if implemented properly. 'Bitperfect'.

 

I don't have a product solution for you; however, while all CD transports have a SPDIF / toslink output and all (true) digital amps currently have an SPDIF input, more and more people are playing their digital audio from PCs and Macs -- it won't be long before the digital amplifier people start usb-equipping their hardware to get that market...

 

On a related note (Chris), what sort of digital signal do the 6th gen Ipods spit out when caressed by the likes of the Wadia Itransport? Get a true digital amp to segue with that and we're all there, 256GB NAND notwithstanding...

 

cheers,

Dave

 

[The Computer Audiophile]

Hey Dave - I have yet to really dig into the iTransport thing much. For me it is kind of a "nice to have" thing, but certainly not a device to run a good quality audio system with.

 

I have a few tests in mind that I want to conduct with a 6th Gen iPod and the iTransport. I'll report back to everyone when I complete the tests.

 

[tfarney]

Dave,

 

If you'll back up a page or two from here, you'll see I'm no longer looking. I found my solution in a Trends UD-10 digital transport. This simple, well-engineered little grey box from somewhere in China takes in USB and puts out both kinds of coax, optical, AES, even analog through a little 16-bit Burr-Brown DAC chip, that sounds surprisingly good, probably because of the transparency of the circuitry around it. It will even do all of them at once if you if you have a need for that, and it seems to do so without adding or subtracting anyting at all. The only drawback I can see is the power supply - a rechargeable battery pack. The advantages of such a psu are linearity, transparency and quiet -- at a cost of a fraction of what an AC supply of similar quality would run. The disadvantage is the extra stuff and the need to re-charge. It might be worth it. The little box reclocks, transports digital and converts it to analog with no muss, no fuss and no added color...for $140.

 

http://www.trendsaudio.com/EN/Product/USB_Audio_desc.htm

 

So the problem is solved. The other problem is that there is something I don't understand that prevents Class D (and T, I believe) amps from creating a headphone out by simply stepping down the speaker amps' output through a nest of resistors. So my Panasonic's headphone jack is powered by a discrete, op-amp based circuit. It's not bad, actually, and I assume it is all digital up to just before the op amp circuit, but then it has to do through a DAC and be amplified without the full benefit of bit-perfect digital amplification. Pity.

 

Tim