USB Class Compliance: For Discussion of Issues & Bugs

Unfortunately, and with great displeasure I have to report the the Allen and Heath CQ-18t does not work with the MPC Live 2. I was really wanting this mixer to work because it sounds amazing and the features are vast. Oh well, I guess I'll be going with the ugly Tascam Model 12.

Error: 44100 may not be a supported sample rate on the external device. Code: -22

Yea, I just bough one. I'll just use the analog connections. The mixer is too dope for me to return it. Hopefully an update will fix this issue.
cb
https://soundcloud.com/cream-of-beats

You guys really should pay attention to specs before dropping money. That thing is "class compliant" with MacOS Core Audio only. If it doesn't work across both Mac and Windows (and Linux), without drivers, its not really class compliant at all.

1-8-8-1 wrote:Behringer X32 compact, (with Klark Teknik DN-32 LIVE card)

Tested working with 32 in and 32 out available.

(FYI this card is a clone of the Behringer branded live recording card for the x32 - Klark Teknik is a Behringer brand)

This setup allows live recording and playback of all 32 tracks to two CF cards in the back of the mixer.
Completely stand-alone, no DAW, continuous recording time limited by the total size of the two CF cards combined. (i.e. very long).

recordings can be pre EQ, fader etc. or can be tapped from anywhere.

no pops and cracks with the latest firmware ?

I have a simple question that might have been addressed before but why can't I just connect the MPC to my computer with 32/32 to a daw like pro tools or cubase?

Because Akai didn't design it to work like that.

I have always wondered if not making the MPC capable of USB device mode results from hardware constraints or if software development could deliver it, with something like the Linux USB gadget g_audio driver.

I'm sure that it's not a hardware limitation: num of channels * samplerate * bit depth = bits / s .
Obviously it's a bit more complex than that (CRC Transfers, polling, interrupt transfers and a bunch of other stuff not included in Isochronous transfer) but our boxes are doing it already but via 2 channels already with ease :/
Ultros managed to demux usb stream into 16 channels some time ago but it was flaky AF iirc.

EDIT:
https://www.edn.com/fundamentals-of-usb-audio/

The USB has sufficient capacity as a bearer. But that does not tell us about what the MPC can do with its chipset: the MPC switching its USB controller to device mode means that it no longer operates as host - which might be acceptable if it just means telling the user that the MPC will detect no USB peripheral when used as a class compliant audio interface... But it may be a problem if internal devices also sit on the USB tree.

But now that I think about it: isn't MPC controller mode implemented by switching to device mode ? If it is, then that answers the question about its ability to do so - and the question that remains is about modprobing the Linux USB gadget g_audio driver.

Edit: As confirmed by this "MPC One doesnt recognize USB Hub in Controller Mode" thread: controller mode is the MPC switching to device mode, its internal hub becoming part of the host's tree.

If the pads, knobs and buttons are on a USB device, then no way to standalone and act as a class compliant USB audio interface simultaneously... That would require two USB controllers aboard the MPC.

Jean-Marc Liotier wrote:The USB has sufficient capacity as a bearer. But that does not tell us about what the MPC can do with its chipset: the MPC switching its USB controller to device mode means that it no longer operates as host - which might be acceptable if it just means telling the user that the MPC will detect no USB peripheral when used as a class compliant audio interface... But it may be a problem if internal devices also sit on the USB tree.

But now that I think about it: isn't MPC controller mode implemented by switching to device mode ? If it is, then that answers the question about its ability to do so - and the question that remains is about modprobing the Linux USB gadget g_audio driver.

Edit: As confirmed by this "MPC One doesnt recognize USB Hub in Controller Mode" thread: controller mode is the MPC switching to device mode, its internal hub becoming part of the host's tree.

If the pads, knobs and buttons are on a USB device, then no way to standalone and act as a class compliant USB audio interface simultaneously... That would require two USB controllers aboard the MPC.

I wished they would just sell a class complaint interface that would support 16 channels stereo 32 mono..

So, we have established that, as it has a single USB controller, the MPC cannot operate simultaneously standalone in USB host mode and in USB device mode hypothetically as a USB class-compliant audio interface.

But, on the other end of the connection, what if the PC has multiple USB controllers ? I see no reason why it couldn't use one for the Linux USB gadget g_audio driver... Has anyone ever tried that ? Hmmm... I wonder what would happen with that PCIE USB2 interface board I have lying around...

It is amazing how this conversation pops up in many places regularly and ends up either in frustration or in recommending the iConnectivity Audio4c which is the only device I have ever stumbled upon anywhere close to a reasonable price for hobby use, that behaves as two class-compliant USB audio devices back to back and has adequate software to manage the routing.

2 x Behringer UMC1820, one for the MPC, the other for the PC. Connect the Behringers with all the digital and analog IO there is, you get 18 mono channels in and out between the standalone MPC and the PC? It can be done if you actually need it.

HouseWithoutMouse wrote:2 x Behringer UMC1820, one for the MPC, the other for the PC. Connect the Behringers with all the digital and analog IO there is, you get 18 mono channels in and out between the standalone MPC and the PC? It can be done if you actually need it.

50% pricier than Iconnect Audio4c, but simple and does the job. But indeed, just because it is possible doesn't mean it is a good idea - thanks for reminding me of my pathological and professional urge to interface everything to everything.

Functionally, exporting a whole project as audio stems and loading it into the DAW is exactly equivalent to recording all channels, if asynchronous... So the only actual use case would be live band integration.

Integrating the MPC into a band with live analogical instruments and a DAW verges on the pipe dream with all the latency and debugging that I don't want to deal with. For my uses, I'll stick to recording instrumentist friends and chopping that into drum programs to peruse in my projects... Simple, fits my purpose, cheaper, I'm not into live anything anyway and I prefer dealing with the aggravation of sequence copying & song mode rather than taking aboard a DAW and all the moving pieces that come with it - I love the MPC's capacity to do everything !

Tried Prism Titan with the Akai Force yesterday and it worked flawlessly in 32 channel mode. No glitches, audio cutouts on recording or playback. Like all audio interfaces must set to 44.1 and turn on and connect with USB BEFORE you power on your Force. I will try later with MPC Live.

If Akai implemented a USB bridge between hardware and computer, this would solve the majority of issues. I'm not an Elektron user, but their Overbidge sounds, in theory, fantastic. Essentially bridging audio I/O from hardware to computer. With the removal of digital I/O on their modern hardware, a second stage of AD/DA conversion is unavoidable. I'm currently utilising all 6x analogue outputs from MPC to my audio interface (RME Fireface 800), it works flawlessly, but I now have two stages of AD/DA conversion. I'm planning on staying with my current setup for now, but am also considering purchasing a RME Babyface Pro FS as a digital bridge between MPC and primary interface (FF800).

Hopefully fuiture hardware releases will provide a better solution for bridging audio I/O.