[btrancho]

I just finish another Alien DAC which I planned to use with an older laptop (Compaq Tablet PC TC1000) acting as a dedicated DAP (running Win XP SR2 / Foobar2000) and connected to my old Onkyo TX904. The Alien DAC tested out fine and works well when connected to my Pimeta. However, when set up as above, it plays fine until I click on another album or song title in Foobar2000 and then drops into a full volume hiss. Can recover from this by clicking back onto the song that was playing or starting another. Once or twice it has spontaneously switched to this full volume hiss when I wasn't even interacting with the laptop.

I've tried using other software (Media Monkey and WMP 11) and get the same problem with them both. I have temporarily switched over to a direct connect from the laptop's headphone out jack and do not get the problem. In both instances I have connected to the receiver's tape in jacks.

Has anyone out there connected an Alien DAC to a stereo receiver? is it my Onkyo? ...the Tablet PC?

Any advice would be greatly appreciated.

 

[eddiewalker]

That's almost certainly a software problem. Have you tried installing the "Asio4All" drivers?

 

[dsavitsk]

The original Guzzler DAC that the Alien is based on would do this if there was a dropout in power. My guess is that the process of switching songs causes a voltage drop to the USB supply. Switching back may simply reset the chip. Try powering it externally.

 

[btrancho]

Thanks for the suggestions. I installed ASIO4all drivers but that did not solve the problem. Before I start to mod the Alien DAC for external power I have a question. Wouldn't the fact that I set up the DAC for regulated power (4.74 measured at the 5V post) mitigate any voltage drops?

 

[kklee]

I've had three Alien DACs with different power configurations exhibit this behaviour on my Presario notebook. I tracked it down to being an issue with the USB port on the notebook. If I connect the DAC through a USB hub, the problem goes away. I think there's enough electrical noise form the USB port that it upset the DAC's timing. Passing the USB signal through a hub seems to clean it up enough to make the DAC happy.

 

[btrancho]

Quote:

I've had three Alien DACs with different power configurations exhibit this behaviour on my Presario notebook. I tracked it down to being an issue with the USB port on the notebook. If I connect the DAC through a USB hub, the problem goes away. I think there's enough electrical noise form the USB port that it upset the DAC's timing. Passing the USB signal through a hub seems to clean it up enough to make the DAC happy.

I just tried something that seems to confirm that, kklee. I switched over to my Thnkpad R50e with the exact same Foobar2000/ASIO4All setup and it's running fine as I type this. - It exhibits none of the mouse-click related or spontaneous hiss that the TabletPC does. Looks like I'm off to pick up a USB hub later today.

Thanks again to everyone who responded.

 

[btrancho]

Unfortunately, adding a USB hub wasn't the solution. I bought a Belkin PC Card USB 2.0 hub that came with an external power adapter. Though it improved the situation a bit - there were fewer instances when the signal was dropped and the hissing took over - it still occurred occasionally and sometimes even spontaneously.

I have to conclude that there is something else going on with the Tablet PC. This is an original model with anemic processing power (1 GHz) and memory (768MB max) limits and runs WinXP like molasses. Still, that should be plenty for Foobar2000.

I'm still open to suggestions. I'll try externally powering the Alien DAC next.

 

[balou]

how 'bout http://www.head-fi.org/forums/showthread.php?t=244751 *shameless plug*

ok,it's basically just what you already suggested - an external power supply with the benefit of not having to mod your existing usb device