USB DAC not working -

[RogerS]

Wonder if anyone can suggest any lines of enquiry. I have a USB DAC that I plug into my iMac (via a Belkin USB powered hub). Up until recently, it was working fine. I then fired up Audio HiJack Pro (after many many months of not using it) and was prompted to Install an Update - which I did. This promptly locked up the iMac to such an extent that I had no control over the sound output...something that Audio Hijack Pro did kept resetting the volume output to max... and took control of the desktop.

A system restore from Time Machine was estimating three days (I kid you not). So I did a restore from my SuperDuper backup drive. All seemed well. The volume control was controllable again. Problem gone away...or so I thought.

However, the USB DAC does not work via the Mac anymore. I checked it on an old PC and it works fine. The Mac recognises that the USB DAC has been plugged in as it then appears in Sound. But also if when I do this I am running a program such as iRecordMusic then it will make this program crash.

So, somewhere, somehow my USB handling of audio seems to have been corrupted.

But where to go next? Reluctant to do a complete re-install.

 

[RogerS]

Given that my SoundSticks (also driven by USB) were working fine, I felt that it ruled out my iMac/USB hub.

So went back to first principles and connected the USB DAC up to an old PC laptop and it worked fine.

Since the Audio Hijack Pro had mucked up my iMac in recent weeks I finally bit the bullet and re-installed the OS. Which went remarkably easily and done in under an hour. All applications, preferences and user data remain the same and the iMac runs a lot more zippily. Tried the USB DAC...still no joy.

Became convinced that it might be a preference file (which I'd previously deleted as part of earlier fault finding) and so rang Apple support for any I might have missed. Deleted a few more for good measure. Still no joy.

But....something the Apple guy said about USB sockets, running hardware checks etc...made me wonder.......and so I tried the USB socket on the hub that was feeding my SoundSticks and Lo the USB DAC worked fine.

So I have two duff USB sockets....one in the hub and one in the iMac...at the same time. What's the chances of that happening? Sod's Law takes precedence

 

[CHJ]

Not all USB sockets are equal, some are power limited (and don't have over-current protection) and will fall over if something is plugged into them that is trying to draw additional current, for charging or powering a hard disk for instance.

 

[Eric The Viking]

The physical USB connector is rubbish too, as I'm sure you've realised. I had one 'work' rather too easily the other day, on one of the kids' e-macs (and yes they do still generally work fine OS 10.5).

On closer inspection, the middle insulator that supports the contacts had snapped off (that bit's 'hermaphroditic', although the metal sleeve isn't). Like many things Apple, it's a pig to dismantle, so I probably won't bother to mend it.

I've had loads of fun trying to sort out Mac USB connections in the past. As Chas says, a lot of them are the low-current sort, particularly the auxiliary ones on the keyboard, and the ones on the back of Mac monitors are limited too on the G4 series.

We're getting a new iMac soon, I believe, so I'm expecting a new can of worms there. Unusually, I may even pay for a maintenance contract this time, as anecdotally they seem not to be very reliable. In contrast, my wife's G4 tower, bought from new, has done almost thirteen years without the slightest hint of a problem. It just keeps on going, currently with OS 10.4 (I could go to 10.5 tops, but haven't). It's only being replaced because it's out of date, and it's a shame really.

E.

 

[RogerS]

.... In contrast, my wife's G4 tower, bought from new, has done almost thirteen years without the slightest hint of a problem. It just keeps on going, currently with OS 10.4 (I could go to 10.5 tops, but haven't). It's only being replaced because it's out of date, and it's a shame really.

E.

Still got my G4 tower but it does creak along a bit compared to the iMac.

It's also about the same vintage as your wife's. Having said that it still is perfectly usable....which is probably more than can be said for a PC of the same vintage. A point that the 'PC's are cheaper' brigade fail to appreciate. How many PC's have they bought within the same timeframe, I wonder?