Touch USB port as digital output to DAC?

[USAudio]

Can the USB port on the Touch be used as a digital-out to stream to an external DAC?

The Touch product description page seems to allude that it is only used as a source of music from USB drives, etc.
It would be nice to be able to stream from the Touch to a USB DAC, such as Ayre's excellent new QB-9: http://www.ayre.com/products_detail....18&field=specs

[JohnSwenson]

Yes the touch can send music to a USB DAC, and it does support 24/96 and asynchronous mode, so it should work well with a QB-9. (I don't have a QB-9 to actually try it out, but I have tried other async USB DACs).

There is one gotcha, it doesn't do it out of the box. The player software doesn't know the USB DAC exits. In order to get music to it you have to modify the alsa configuration to tell the player software to send the stream there. This can be done manually (SSH into the touch and create a file).

I'm working an an applet that will let you choose which output devices you want to send music to. Hopefully it will be done by the time you can actually get a touch.

John S.

Shameless plug: If you really want to be sure the QB-9 will work with the touch I'll be glad to try it out if you loaned it to me for a week or so!

John S.

[Mnyb]

Ok Is this preferable to spdif ? USB ?
Hmm my MeridianG68J has an USB input have to figure what that one does ?

[jacobdp]

In almost every case, the Touch's S/PDIF output will be better than the USB receiver built into a DAC; the only exception is devices which support asynchronous USB (made by Wavelength Audio and a very few other manufacturers more recently). If you don't know what asynchronous mode is / your DAC isn't touting it as a major feature, you probably don't have it.

[Mnyb]

This is probably the case, I have to investigate interesting paper at ayre.

The Meridian processor probably have this for compatibility with all things.
These processors are often used by installers who works for rich people .
So it is required to work with "everything" .

[JohnSwenson]

The subject of S/PDIF VS USB DAC is not cut and dried. As with just about everything else, "it depends".

The QB-9 is going to out perform just about any S/PDIF DAC you connect to the Touch. Both the S/PDIF and USB connections on the Touch are really good so its going to depend very much on the details of the DAC. With this USB out a large number of even inexpensive USB DACs might very well sound better than a large number of the S/PDIF input DACs.

Strange as it may sound many of the inexpensive USB receivers are quite sensitive to the particular implementation of a USB port. Most general purpose computers have very uneven timing on their USB ports which adds jitter to the PLL generating the local clock in the receiver. While this does not cause data loss, it can significantly increase jitter. The USB port in the Touch has a much more uniform timing so inexpensive receivers will do a much better job than they do with most computers.

So a USB DAC that sounds so-so on most computers can sound quite a bit better on a Touch.

Then again the S/PDIF output on the Touch is also very good. This makes it almost impossible to make generalizations about which is going to sound better.

I have a DAC with very good DAC chips and analog implementation, which has a cheap USB receiver tacked on. When the USB is plugged into all my other computers the S/PDIF from the touch easily blows the USB out of the water, but with the USB plugged into the Touch its so much better that its really hard to tell the difference. A slightly less quality S/PDIF receiver implementation in this DAC would have tipped it towards the USB when plugged into the Touch.

John S.

[joelha]

Any developments on an app to make this option possible?

I would love to make this modification on my Squeezebox.

Thanks,

Joel

P.S. Will be in Hong Kong this week and will hear the Magico Ultimates. At $400,000 a pair I'm not such a likely customer, but what a treat.

[Kal Rubinson]

Can the USB port on the Touch be used as a digital-out to stream to an external DAC?

The Touch product description page seems to allude that it is only used as a source of music from USB drives, etc.
It would be nice to be able to stream from the Touch to a USB DAC, such as Ayre's excellent new QB-9: http://www.ayre.com/products_detail....18&field=specs

It can certainly be done and, as John has pointed out, can be advantageous in some cases. I thought so: http://forum.stereophile.com/content...k-music-player

Kal

[joelha]

Thanks for the reply, Kal.

Where can I find the instructions to make this happen?

The Ayre link appears not to be good anymore and of course, I've read your excellent article on the Touch which started this madness for me in the first place.

With USB only DACs, this solution is critical.

Joel

[Kal Rubinson]

Thanks for the reply, Kal.

Where can I find the instructions to make this happen?

The Ayre link appears not to be good anymore and of course, I've read your excellent article on the Touch which started this madness for me in the first place.

With USB only DACs, this solution is critical.

Joel

It was posted by John Swenson on another thread here.