Hi,

I recently got an Edirol UA-1EX, mainly for use as a budget USB DAC to connect my computer to my amplifier. Everything was working great, until I noticed distortion when listening to bass-heavy music.

At first I thought I was overloading the inputs to my amp, but this turned out not to be the case, as the distortion is also there when I connect it to other devices, and through headphones plugged directly into the UA-1EX's headphone mini-jack.

Strangely, it only distorts when the device is in "advanced" mode, not in "simple" mode. The difference between this modes is that in advanced mode it uses Edirol's drivers, and in simple mode it operates as a generic USB audio interface using the OS built-in driver. But the apparent loudness is the same in both cases, similar to other line-level devices.

In advanced mode, I have to turn the overall system close to maximum for the distortion to appear. But in simple mode, there's no choice - the system volume becomes greyed-out (read-only) at maximum - but there is no distortion.

The UA-1EX is connected to a USB 2.0 socket on my first-gen Intel iMac running OS X 10.5.4, with the analogue line outs connected directly to my amp. I have the latest OS X drivers from Edirol, version v1.1.2. I'm not using any of the other I/O including digital in the UA-1EX, and the other dipswitches on it don't make any difference.

The distortion itself sounds inconsistent, like semi-random high pops and crackles, generally clustered around loud bass drum notes, kind of like digital break-up, sometimes in one channel or the other. It's not very obvious, I only noticed it using headphones.

I can post recordings of the unit in both simple and advanced mode if it helps.

Any ideas what could be causing this?

Thanks, Xen

Update - I contacted Edirol support about this.

They said it should not be happening, and there is not really a lot of difference between Advanced driver ON or not. They confirmed that with Advanced driver OFF the unit is recognised as a generic USB audio interface and uses the OS built-in driver.

I suggested that since the distortion is only there in Advanced mode, it sounds like it's occuring in the digital domain - perhaps a driver problem, or some kind of conflict between the driver and something else (it sounds more like a digital kind of break-up to me anyway, if there is such a thing).

However Edirol said there are no known issues with the drivers. They also said "we find it difficult to imagine a situation where the driver would affect the hardware in any way" which again suggests a software issue...

I sent them 2 recordings I made of the UA-1EX playing back the same audio from iTunes, one in simple mode and one in advanced mode, so they could hear the problem themselves.

They responded that they listened to the files but "to us, they sound exactly the same".

I wasn't expecting that !!! Now they're saying simply, if I'm not happy with the unit I should return it to the dealer for a refund. So this avenue has reached a dead end.

I don't really want to return it, because I'm happy using it in simple mode for the time being. I'd prefer to get to the bottom of it and understand what's causing the distortion in advanced mode, even if I have to work around it by turning down the system volume until the distortion is no longer audible.

I would like to upload the same test files here, to see what people here think. But this forum doesn't allow attachments. If nobody has any other suggestions I might try and upload them in the Uploads forum and link to them here.

Here we go:

Edirol-UA-1EX-simple.24bit.flac
Edirol-UA-1EX-advanced.24bit.flac

In both cases the UA-1EX line outs were connected directly to an external mixer, and then routed back in to the imac via a different audio interface which was attached by FireWire.

The only change I made in between these 2 recordings was to switch the UA-1EX from simple to advanced mode, and then unplug its USB plug and plug it back in, in order for the change to take effect.

iTunes volume was at max, and the OS X system volume was also at max, in both cases.

Hmm... have you tried by increasing playback buffer (i.e. latency)?

Juha

Thanks for the suggestion. I tried setting the latency in the UA-1EX driver properties, and it didn't make any difference.

While doing more tests, I just noticed that if I play audio from Apple Logic, there is no distortion, even with the UA-1EX in Advanced mode, and even with the latency set to the minimum in both Logic and the UA-1EX driver. The distortion is there when using iTunes as the source app and the UA-1EX in Advanced mode.

Interestingly, when the UA-1EX is set to Advanced mode, it shows up in Audio MIDI Setup.app as a 24 bit / 44.1 KHz device, whereas in Simple mode it shows up as a 16 bit / 44.1 KHz device. I can't see any way to change the bit depth other than switching between these modes.

Could this be the key to the problem - i.e. in Simple and Advanced mode, Logic sends 16 bit or 24 bit audio to the driver as needed, whereas iTunes always sends 16 bit audio, and "something" fails to convert it correctly to 24 bit, when the UA-1EX is in Advanced mode? If so, what is responsible for doing this conversion - OS X or the Edirol driver?

Does anyone else with an UA-1EX under OS X have time to confirm whether or not they get the same behaviour?

Hi,

yes, I found the same behaviour with my UA-1EX under OS 10.5.5. In advanced mode I have to turn down the output volume to avoid distortions. By the way, do you think that these distortions are what people call "clipping" and might damage my tweeters?

Greets,
Bob

Thanks Bob, it's gratifying to find someone else has experienced the same behaviour, and I'm not going mad!

What application are you using to play the audio? I found the distortion was there with iTunes but not Logic. Also have you done any other tests to confirm that it is not caused by your amplifier or anything else further down the chain being overloaded? For example, have you listened through headphones plugged directly in to the UA-1EX to check whether the distortion is there too, even with the physical headphones output volume control on the UA-1EX turned low (it was for me)?

Even without additional tests, it seems to me it can't be clipping outside the UA-1EX, because as you said the distortion only occurs with the UA-1EX in advanced mode - and the max volume in advanced mode is no louder than the fixed volume in simple mode which does not distort (with all other things staying equal).

Regarding "clipping" - the distortion doesn't exactly sound like analogue clipping to me - but clipping is just one type of distortion, caused by signal overload. All I can say for sure is it's "distortion" of some kind.

In terms of tweeter damage - I would have thought that any type of distortion containing concentrated bursts or peaks of energy, like loud pops or cracks, could potentially cause damage, but ONLY at high volumes - at lower volumes I wouldn't worry about it!

Any other UA-1EX owners out there who get the same behaviour, or who can do tests like this?

Xen

I'm getting the exact same thing with my old Edirol ua-20, its quite old though, might just be a bit knackered.

Is it normal for it to be doing this after a few years of use? Seems like a bit of a poor show to me... I was thinking about getting a UA-1Ex to replace it but now I'm not too sure.

A member of head-fi was recently using the UA1-EX to perform tests on cables. He was having some troubles because the ADC was not functioning reliably.

Head-Fi Cable Test