Mbox adding noise/distortion - where to repair?

[tcline]

Several months ago, my mBox started adding a scratchy distortion to the audio running through it, into Pro Tools. Only happens when I try to record something. I've removed all other equipment that might be causing this, but no matter what input method I use (mic, audio source, guitar, etc) I get the noise. Thinking it might be the computer somehow, I tried upgrading from PT 6.1 to 6.4, upgrading the ASIO driver, upgrading the Mbox firmware - and when none of that made any difference, I completely blew out the original installation, and reinstalled from the original disks. That was a fun four hours...Still, I get the noise.

Digidesign website says that Focusrite now does repair on these, but when I called them in Agoura Hills, they said absolutely not, they make a competing product and Mbox is all Digidesign. Argh.

Anybody have a similar problem? Anybody know how/where the box can be checked and possible repaired, if that is even a possibility?

[spkguitar]

Are you sure it is the mBox hardware causing the problem? Does the noise happen in other programs?

Have you tried raising the hardware buffer?

[tcline]

Thanks for the tip - and we're onto something here. By changing the H/W buffer size to any other value (Setups|Mbox settings|H/W Buffer Size), the problem goes away - but hold on - when I click OK in the dialog box, it comes right back, regardless of the value set! Same with the DAE Playback Buffer setting - change it, problem stops. Click OK, problem comes back.

The only other "recording" I do with this machine is rip the occasional mp3, using iTunes, and never had a problem with sound quality.

I am not a tech guy - but doesn't this point to a computer hardware problem of some sort, or just the way PT is using the hardware available?

I am using a P4 3.0, 1 Gb ram, I have two hard drives, both SATA, 36 Gb. Windows XP Home. Everything else seems to run great on this computer, and PT/Mbox were running great up until about December of 2005. I have hyper-threading turned off...but where else might I look, any hints?

One last clue - when turning the input/playback knob, I can definitely hear a slight delay when moving from input (7:00) to playback (5:00). Right around straight up (12:00), it is very very apparent. When I monkey with the settings per above, while the audio source is playing, the delay goes away, and the further I turn the knob to the right (towards playback), the quieter the sound, as I believe is the proper behavior. When I am getting the noise, I am getting sound in all positions of the knob. Shouldn't I be getting NO sound, when the knob is all the way to the Playback side, when I am just recording?

[spkguitar]

Try all of the solutions in the General Troubleshooting thread first, up to and including the last item about posting specifics using SiSoft Sandra.

[tcline]

Thanks for the ideas - upgrading to Windows XP Service Pack One apparently did the trick, or at least most of it, as I have lost the distortion. I am still getting some latency when overdubbing, but will do some research to find out what to check for. This thread is done as far as the distortion problem goes, thanks again.