LinuxMusicians

So, this is the only device I know of with 4 actual built-in preamps at 24-bit, all bus powered. I want it to work. I don't get xruns, everything seems working, but I hear a pretty decent amount of modest-level crackles. I don't get such crackles with my Focusrite Scarlett 2i2.

I'm at a loss. I'm on KXStudio 14.04 with all the latest updates.

Any suggestions?

I get crackles out my gear if I over load the output, such as when playing a soft synth with a midi keyboard out of my interface.
To prevent this I always put a limiter on the output (typically Steve Harris fast look ahead limiter, which does not seem to affect latency). Specifically I play my synths and samples by loading them in Ardour and put the limiter on the master channel. That way no matter how many instruments I play at once I won't over load the output.

Other than this I can only suggest trying different jack options, and running the interface on another OS to trying to isolate whether the problem in software or in the interface itself.

If the previous good tips don't work, try with a powered usb hub, that's a lot of gear to rely on bus power,
despite the marketing dept view. And try using a heavy-duty extension cord,
on some different circuits. Maybe a dedicated power supply, if old grounding
is in place. Looks like a great interface and pricing!

glowrak guy wrote:If the previous good tips don't work, try with a powered usb hub, that's a lot of gear to rely on bus power,
despite the marketing dept view. And try using a heavy-duty extension cord,
on some different circuits. Maybe a dedicated power supply, if old grounding
is in place. Looks like a great interface and pricing!

Still need to try the previous advice about clipping, but the powered issue is a significant factor in my liking this. At any rate, no need for a powered hub, the thing comes with a power adapter as an option, despite it functioning bus-powered. I can try the adapter to see if it helps.

So far, it's really hard to pin down. It seems it might relate to overloaded output, but limiter didn't make it really fixed, hard to tell if it was an improvement. Switching to the separated AC power adapter was weird in that it loses USB connection during the switch, but wasn't crackle-free afterward. It may relate to CPU overload, but hard to say there. It's not terribly awfully crackly, but definitely more than my Focusrite. So, hard to say… arg. I wish there were some way to identify a particular exact reproduction, because right now, the best I have is playing some sound and hearing some crackles, but it's not a particular point.

I definitely do *not* get crackles just because I overload the signal. I can get distorted overloaded output that doesn't always have crackles. And I can get crackles with the power plug. And without xruns.

Try it in Windows, see if it behaves similarly or not, just in case the hardware is duff.

I have a UMC404 (if there's a difference to the 404HD I haven't yet been able to find it) and it works OK under Linux.
Perhaps it's worth checking with Behringer support what the latest firmware is for that model and to update it in case it's got an old one.

Are all the preamps set to the same phantom or non-phantom power? Does the manual cover this?
I read that Tascam units could be damaged or fry when changing those phantom settings with the units powered on,
due to poor low-cost design, so be careful, and power off between such changes.

A behringer rep at KVR confirmed that the new HD version is an improved ciruit design
to properly support 192mkz, and that the latest firmware is designed for misc compatibility,
not to advance the earlier model's beyond 96mkz. One guy reports happily using the HD live at 64 samples.

http://www.kvraudio.com/forum/viewtopic ... 2&t=402117

and luck rises turning off bluetooth, network managers, power management, webcam, hal device polling yada yada

Maybe try a few live distros having different kernels, tango, avlinux, bodhi with kx repo added, and some newer kernels, 4.1/4.2.
Cheers

Did you ever find the cause of this? I have just picked one of these up and I am noticing more glitches (perhaps xruns, I'm not sure) than I had with my focusrite.

I was tempted to test again (I have much updated setup otherwise), and I still have the interface. But I'm just usually using my Focusrite now and have not been lately needing all 4 channels and not trying the UMC. I hope it will work well when I get around to trying it again. It's not my priority right now.

UPDATE: My friend got the same unit, and his doesn't crackle! Tested with my system. I just had a bad unit all along!!

Just maybe a firmware update will help or something, but maybe it needs repair. Anyway, this isn't an issue overall, just I have a bad case. Ugh. I wish I'd considered the possibility initially when I could still return/repair/exchange under warranty instead of finding this out 4 years later.

Mine works OK, as long as I am using a real time or low latency kernel.

I'm on low-latency kernel. Anyway, it's clearly nothing at all on my end. I literally have two units to test now, and my friend's unit simply works, while mine is crackly. We're talking about literally just swapping the two on my exact same computer. It's was just a bum unit all along.