List of Working/Non Working Class Compliant USB Interfaces

Neodymium wrote: So it started to crackle? Nothing else was connected, just the UMC, no Octatrack, nothing, just the UMC?, Just MPC, UMC, Speakers

No, with everything still connected. The crackles started again when routing them to the Octatrack and back again.
When not routing them to the Octatrack I had no crackles.
I know that the Octatrack is not causing the crackles since when monitoring the Octatracks outputs through the headphones of the Octatrack, there are no crackles. It's once they get back to the UMC that they appear, leading me to think that there is some strain/mismatch happening when routing like this
Tried with my friends XR18 also, and the experience was almost identical.

Your approach and reasoning is different to mine. Good luck I hope you get it sorted.

horisonten wrote:

Neodymium wrote: So it started to crackle? Nothing else was connected, just the UMC, no Octatrack, nothing, just the UMC?, Just MPC, UMC, Speakers

No, with everything still connected. The crackles started again when routing them to the Octatrack and back again.
When not routing them to the Octatrack I had no crackles.
I know that the Octatrack is not causing the crackles since when monitoring the Octatracks outputs through the headphones of the Octatrack, there are no crackles. It's once they get back to the UMC that they appear, leading me to think that there is some strain/mismatch happening when routing like this
Tried with my friends XR18 also, and the experience was almost identical.

You are likely overloading your MPC. 10 duplex audio channels and 5 audio tracks are going to put a strain on the machine. You’d be better off returning the UMC and getting a mixer with a submix out on it, plug whatever into the mixer and if you need to record, use the submix into the MPC. Same result, except only using 2in 2out on the MPC.

enzyme wrote:You are likely overloading your MPC. 10 duplex audio channels and 5 audio tracks are going to put a strain on the machine. You’d be better off returning the UMC and getting a mixer with a submix out on it, plug whatever into the mixer and if you need to record, use the submix into the MPC. Same result, except only using 2in 2out on the MPC.

Like mentioned earlier the project with the issues uses 30-40% cpu, and currently 47% memory usage.
You really think that I'm straining the MPC even though not even using half of the MPCs available hardware resources?

Unfortunately I do not have room for a mixer in my flightcase setup. The audio interface must be of 1U size, and of "set and forget" type since it is fiddly to reach.

And a general update to what I have mentioned earlier. The routing to and back from the Octatrack was not causing the crackles after all.
Tried again yesterday, and even though sending everything directly to Out 1/2, the very noticable crackle on sequence change is still there.

I'm seriously considering switching to Ableton Push 3 Standalone. From the reports I've seen the class compliant audio functionality on that one seems to be working a lot more reliable, even though only been available since September 2025 firmware.

Was the Octatrack synced to the the MPC

Neodymium wrote:Was the Octatrack synced to the the MPC

No, the MPC is slaved to the Octatrack.
But making the MPC the Master doesn't make any difference, just tested.

I have an ongoing support ticket with Akai regarding this. I'm starting to suspect that there is something wrong/corrupt in the actual project, or that there is something wrong with my actual MPC converters.

The project was originally created in 2.15.1, then imported in 3.7 without issues.
But I have noticed that sometimes the previous sequence is playing on the MPC, even though the UI shows me that the next sequence is playing. I need to manually change sequences on the MPC to make things "kick back in". This makes me suspect some corruption in the project. Unless there is a bug in 3.7 that is not reported yet...
I'll add the last finding to the bug reports also just in case.

horisonten wrote:This makes me suspect some corruption in the project.

Then try with a clean project..Don’t try to replicate it just bang another project..Also a nice reset of system prefs is a smart move if you haven’t done that already..

horisonten wrote:

Neodymium wrote:Was the Octatrack synced to the the MPC

No, the MPC is slaved to the Octatrack.
But making the MPC the Master doesn't make any difference, just tested.

So yes, synced.
I assume USB, not midi 5 DIN cable ?

Did you see if removing the USB cable stopped the crackling?

Yorgos Arabatzis wrote:Then try with a clean project..Don’t try to replicate it just bang another project..Also a nice reset of system prefs is a smart move if you haven’t done that already..

Yeah, but its not as easy as just start with a clean project. This is my supposed liveset with like 40-50 sequences with sequencer data.
So it is quite the effort to do it all over once again...
I've already gone from 3.4 to 2.15.1 and then back to 3.7 the manual way...

Neodymium wrote:So yes, synced.
I assume USB, not midi 5 DIN cable ?

Did you see if removing the USB cable stopped the crackling?

Octatrack doesn't do midi over usb, so no usb between them. Old school 5 pin.

I thought you had tested with a clean project with this set up?

horisonten wrote:So in my desperate search for crackle free operation I started a new test project.
Loaded like 4 plugins, a drum program and a drum program with only risers.
And it started well. Memory usage was 50% and cpu like 17-20%. And at first it was crackle free.

But then when routing like I usually do, out 5/6 from the UMC to my Octatrack Input A and B, and out 7/8 to Octatrack Input C and D, there was a few crackles again.
Then my Main Out and Que Out out of my Octatrack comes into the UMC 1/2 and 3/4, these are then sent directly to Main Out 1/2 (to the PA/Speakers).

I want to route everything thru my Octatrack for live mangling and effects. And I'm starting to suspect that this routing is causing some kind of strain on the MPC/UMC combo

So with this, You had MPC connected to the UMC via USB. 4 mono outs (2 stereo pairs) the to the Octatrack, and 4 mono outs (2 stereo pairs) back to the UMC. The UMC was synced to the Octatrack via Midi cable, and there were no other devices and connected, and the USB on the Octatrack was not used?

You tested the Octatrack signal on the headphones, which was fine. I'm guessing you don't have a mixer to test the 2 stereo outs of the octatrack. Does the crackling happen when all the inputs on MPC are muted on their tracks?

Neodymium wrote:I thought you had tested with a clean project with this set up?

So with this, You had MPC connected to the UMC via USB. 4 mono outs (2 stereo pairs) the to the Octatrack, and 4 mono outs (2 stereo pairs) back to the UMC. The UMC was synced to the Octatrack via Midi cable, and there were no other devices and connected, and the USB on the Octatrack was not used?

You tested the Octatrack signal on the headphones, which was fine. I'm guessing you don't have a mixer to test the 2 stereo outs of the octatrack. Does the crackling happen when all the inputs on MPC are muted on their tracks?

I tested with a new project, very simplified, but nonetheless new project. It worked initially, but then the crackles started when starting to route things to the Octatrack. But then it didn't go away when routing things back to the 1/2 out again.

I'm pretty sure the crackling goes away with muting the inputs. Need to double check, but I managed to at least pinpoint the Monitor In on audio tracks as the cause of the crackles.

horisonten wrote:
I'm pretty sure the crackling goes away with muting the inputs.

If the crackling goes away when you mute the inputs, that to me suggests the crackling is on the audio signal. I know you tested the headphone output, which is a good indicator, but it's not the same as testing the outputs themselves.

However, if the crackling doesn't go way when muting the inputs, that indicates its part of the system creating the noise, and not a signal issue.

Neodymium wrote:If the crackling goes away when you mute the inputs, that to me suggests the crackling is on the audio signal. I know you tested the headphone output, which is a good indicator, but it's not the same as testing the outputs themselves.

However, if the crackling doesn't go way when muting the inputs, that indicates its part of the system creating the noise, and not a signal issue.

Now I have tested some more.
Removed all cables from the UMC as suggested earlier = no crackling.
Muted the Audio tracks = also no crackling.

But I have also tested each individual gears outputs with another mixer. Everything else is connected the same, only the output of one device at a time is connected to the second mixer = also no crackling. The signals of all devices are clean!

So something is happening as soon as I enable Monitor In with audio playing... Like said, muting or having Monitor set to In with nothing connected = no crackling.

And also, just to rule out audio levels. The crackling is still there when lowering each device by like 50%. So it cannot therefore also not be that my levels in are too hot.

Neodymium wrote:So with this, You had MPC connected to the UMC via USB. 4 mono outs (2 stereo pairs) the to the Octatrack, and 4 mono outs (2 stereo pairs) back to the UMC. The UMC was synced to the Octatrack via Midi cable, and there were no other devices and connected, and the USB on the Octatrack was not used?

You didn't respond to this.

horisonten wrote:Muted the Audio tracks = also no crackling.

Was that with Monitor set to In?

horisonten wrote:And also, just to rule out audio levels. The crackling is still there when lowering each device by like 50%. So it cannot therefore also not be that my levels in are too hot.

When you lower the track levels in MPC does the crackling decrease too, or stay the same. This should indicate if it's the crackling is part of the audio signal or the part of the system. Back in the firewire, and pre USB 2 days, if buffer setting were too short, or the system overloaded, the crackling was a system noise, not and Audio signal.

Also if it is is changing with the mixer level, is it both stereo pairs from the octatrack or just one or the others.

Have you tried removing the octatract from the equation. Send the signal out the 2 stereo pairs, but then run the cables back into the inputs, routing that straight back in through the 2 tracks the octatrack was on.