USB Audio Interfaces and Latency ...

[SamIAm]

I really quite like my MOD Dwarf multi f/x ... the one thing it does not do (And I really wish it would) is support on device configuration of presets.

Connect a device (laptop/tablet/phone) via USB and fire up a web browser and OMG you can do amazing things, but once disconnected the 'tweakability' on the Dwarf itself is constrained to swapping presets (pedalboards in the MOD lingo), snapshots and using the onboard knobs/switches to tweak some things (for instance the wet/dry mix, active/bypass, rate, etc elements of the different plugins, the equivalent of pedals), these are things that you have defined using the web UI; but I don't want to have to use a laptop/tablet as part of my live rig.

 

There are some who have used the MOD software (which is open source bless them) running on a Raspberry Pi and added in some extra capability.  Before I got my Dwarf, I'd done the same ... but when using a Pi approach the way most go (as did I) is to use an add-on audio card on the Pi.  This is a tidy solution, but I found that I was getting noise using this approach (The Pi radiatees digital EMI and the adjacent audio card picks it up) also, I've not been able to find one of these that is not just 2x Mono In/Out or 1xStereo In/Out.

 

So ... what about using a USB audio interface (Such as a Focusrite Scarlett 4i4) to provide better noise isolation and get 4xMono In/Out !?

 

My intent would be to mount the USB Audio Interface on a physical pedalboard along with a Pi based custom built, small as a small thing, cute as a button computer (With a display and knobs/switches on it) to run a DAW (Well, most likely the MOD open source software with some customisations to allow patch editing in a similar way to a HX Stomp/GT-1000 Core) so that the whole shooting match is on a single portable board, but more importantly is fully self contained.  The new Pi5 is shipping soon and it is stonkingly powerful, it's just the performance (especially latency) of the USB Audio interface that is a big unknown to me.

 

And so to my question(s)

What has been your experience of using USB audio interfaces for live effects?  I suspect the most common setup would be to have a PC or Laptop with a DAW running plugins and using a USB audio interface.

What sort of round trip latency have you been able to get down to? (Straight in/out, without any plugins running in the DAW)

Is it usable live, or is the delay too great?

Which USB audio interfaces have you found to be great (or not so great)?

Are there any 'real' USB 3 Audio interfaces?

 

S'manth x

Edited November 16, 2023 by Smanth

[MrDinsdale]

I have a Focusrite Scarlett 2i2 and when connected to my MacBook (m1) I get around 12ms round trip latency with Logic. Sounds like a fun project!

[SamIAm]

8 hours ago, MrDinsdale said:

I have a Focusrite Scarlett 2i2 and when connected to my MacBook (m1) I get around 12ms round trip latency with Logic. Sounds like a fun project!

Which generation is the 2i2?

S’manth x

[chyc]

Be careful with Focusrite and Linux. They do not sit well together sometimes so check that the interface is "Class Compliant". This is usually to hoover up the iPad market, but if Linux gets thrown a bone in the process then no complaints from me  

 

I have a Pi4, and sometimes plug in an SSL2+ interface. It isn't great. Here are things that I found:

 

• It couldn't cope with recording, although I wasn't trying it seriously
• Power draw is a real issue. If your interface takes too much juice from the USB, then it won't start. I cannot use 48v phantom power for example. An interface with separate power source would be much better.
• Messing around with latencies is a bit of a pain. If I took it too low (4ms) then it sounded awful. I cannot remember what I ended up using but it was definitely double digits, which is absolutely fine for recording (not that I could record)

I don't own a Pi5, but as I understand it, it is as fast as a Pi4 unless you put active cooling on it. Bear that in mind when you buy it. If I were doing it seriously I wouldn't think about Pi5 at all: I'd get a second hand Intel laptop. I don't know if this MOD software has been compiled for amd64, but I would be surprised if it hadn't. Pi is really, really good at certain usecases. I have one that I can just leave on as a router, because its power consumption is so low. For a gig, you'll probably be chewing through >100W just through your amp and so the difference of 10W is just going to be line noise. Pis (especially their SD cards) aren't great for reliability either.

 

Sorry to throw a damp towel over your project. It certainly would be fun and I may try it myself one day, but I would personally never ever rely on it for gigging. I've had multiple Pis die on me, which because I'm using them for fun projects is fine. Admittedly these are the older pis and things may be better now.

[Matt P]

I've never tried to use My interface as a live effects unit but I am one of those people using an Interface with Linux, I found that unless the Interface was class compliant I had issues, so my 18i8 required additional software to work properly, i think i could get 2 channels working (it was a long time ago) but any more was impossible.

 

I ended up buying a 2i4 to use on my Linux machine and keep the big setup for use with a windows laptop.

 

I've been told that if you configure the interface using a windows machine then swap to linux it should work but i've not tried that yet.

 

I'm using Reaper as my DAW and luckily there is a Linux version (which works very well)

 

Matt

[BigRedX]

The problem with multiple-channel interfaces is that they generally rely on a dedicated "control panel" app to configure the routing and other functions and that no Linux versions of these apps exist. Therefore at the moment under Linux you only get 2 in, 2 out functionality and only if the device is "class compliant". However there is good news for owners of current Focusrite interfaces in that there is 3rd party development of a routing application happening with Focusrite's blessing and support.

[SamIAm]

17 hours ago, MrDinsdale said:

I have a Focusrite Scarlett 2i2 and when connected to my MacBook (m1) I get around 12ms round trip latency with Logic. Sounds like a fun project!

I need to have a fun electronics project on the go

S'manth x

[MrDinsdale]

9 hours ago, Smanth said:

Which generation is the 2i2?

S’manth x

Mine is the 1st gen. 

[SamIAm]

8 hours ago, chyc said:

Be careful with Focusrite and Linux. They do not sit well together sometimes so check that the interface is "Class Compliant". This is usually to hoover up the iPad market, but if Linux gets thrown a bone in the process then no complaints from me  

 

I have a Pi4, and sometimes plug in an SSL2+ interface. It isn't great. Here are things that I found:

 

• It couldn't cope with recording, although I wasn't trying it seriously
• Power draw is a real issue. If your interface takes too much juice from the USB, then it won't start. I cannot use 48v phantom power for example. An interface with separate power source would be much better.
• Messing around with latencies is a bit of a pain. If I took it too low (4ms) then it sounded awful. I cannot remember what I ended up using but it was definitely double digits, which is absolutely fine for recording (not that I could record)

Thanks for your reply.  What you describe about the latency is what concerns me . I gather that linux kernel 5.16 introduced some improvements in this space.

 

8 hours ago, chyc said:

I don't own a Pi5, but as I understand it, it is as fast as a Pi4 unless you put active cooling on it. Bear that in mind when you buy it. If I were doing it seriously I wouldn't think about Pi5 at all: I'd get a second hand Intel laptop. I don't know if this MOD software has been compiled for amd64, but I would be surprised if it hadn't. Pi is really, really good at certain usecases. I have one that I can just leave on as a router, because its power consumption is so low. For a gig, you'll probably be chewing through >100W just through your amp and so the difference of 10W is just going to be line noise. Pis (especially their SD cards) aren't great for reliability either.

I'm not sure many people do have a Pi5 yet, I've ordered one but unlikely to get it this side of 2024!  I gather from the paper specs that it is improved over the Pi4 from both a CPU and IO perspective, but the acid test would be of course to test it out.  I'd most likely be running the MOD open source s/w on it, the MOD Dwarf uses a Cortex A-35 @ 1.3GHz, the Pi5 Cortex A-76 specs are significantly better (twice the cpu closk speed/larger L1/2/3 caches/faster memory IO/etc) ... I have had the Mod s/w running on a Pi4 using a hat based audio card (HiFiBerry) and performance was OK, I'd expect the Pi5 to fly, but I had a noise issue ... paper specs says the USB is better as they have rearchitected the IO controller. And they have added support for M.2 SSD so SD failure can be avoided.

 

MOD have released varients of their software that run on Windows/Linux/Mac but a laptop is going to be too large , whilst I will want to incorporate some knobs/switches/stomp switches and a display, it will still be wee.  My aforementioned Pi4 device was tiny!  You can see how it compared in size ...

 

 

8 hours ago, chyc said:

Sorry to throw a damp towel over your project. It certainly would be fun and I may try it myself one day, but I would personally never ever rely on it for gigging. I've had multiple Pis die on me, which because I'm using them for fun projects is fine. Admittedly these are the older pis and things may be better now.

No damp towel  , just some stuff I need to take into account, this sort of feedback is why I love BC!

 

S'manth x

 

 

[SamIAm]

 

8 hours ago, Matt P said:

I've never tried to use My interface as a live effects unit but I am one of those people using an Interface with Linux, I found that unless the Interface was class compliant I had issues, so my 18i8 required additional software to work properly, i think i could get 2 channels working (it was a long time ago) but any more was impossible.

 

I ended up buying a 2i4 to use on my Linux machine and keep the big setup for use with a windows laptop.

 

I've been told that if you configure the interface using a windows machine then swap to linux it should work but i've not tried that yet.

 

I'm using Reaper as my DAW and luckily there is a Linux version (which works very well)

 

Matt

USB class compliance seems a must!  I've seen a review of the MOTU M4 (Which uses class compliant USB) and using jack/alsa/qjackctrl it supports all 4 in/outs:

 

The MOD software is built on top of Jack so should work (Of course until I actually try it ...) it's the latency that concerns me 🧐

S'manth x

[SamIAm]

 

8 hours ago, Matt P said:

I've never tried to use My interface as a live effects unit but I am one of those people using an Interface with Linux, I found that unless the Interface was class compliant I had issues, so my 18i8 required additional software to work properly, i think i could get 2 channels working (it was a long time ago) but any more was impossible.

 

I ended up buying a 2i4 to use on my Linux machine and keep the big setup for use with a windows laptop.

 

I've been told that if you configure the interface using a windows machine then swap to linux it should work but i've not tried that yet.

 

I'm using Reaper as my DAW and luckily there is a Linux version (which works very well)

 

Matt

 

8 hours ago, BigRedX said:

The problem with multiple-channel interfaces is that they generally rely on a dedicated "control panel" app to configure the routing and other functions and that no Linux versions of these apps exist. Therefore at the moment under Linux you only get 2 in, 2 out functionality and only if the device is "class compliant". However there is good news for owners of current Focusrite interfaces in that there is 3rd party development of a routing application happening with Focusrite's blessing and support.

 

USB class compliance seems a must!  I've seen a review of the MOTU M4 (Which uses class compliant USB) and using jack/alsa/qjackctrl it supports all 4 in/outs:

 

The MOD software is built on top of Jack so should work (Of course until I actually try it ...) it's the latency that concerns me 🧐

S'manth x

[chyc]

OK, I got my SSL 2+ plugged into my Pi4, running Ubuntu Mantic with Linux Kernel 6.5, compiled for low latency. I was able to get a latency of 5ms using a buffer size of 160 with a period of 3 (I think: don't want to spoil the punchline of why I cannot remember). I had Guitarix running with chorus, a cabinet IR and reverb running with 1 buffer underrun according to qjackctl.

 

All was going great, the latency was well within my own limitations as a musician and I was able to play along to my hifi in the room. That was until my Pi crashed and I had to reboot. Now granted I've just upgraded my OS so it may have gremlins still, but I absolutely wouldn't want to rely on this setup out on a gig. It also took multiple attempts of plugging and unplugging the interface for the stars to align and the Pi give the interface enough current for it to start-up.

 

This is an aside, but I thoroughly recommend people try out integrating their Jack setup into Pipewire (an alternative to Jack). I've been frustrated in the past not being able to e.g. listen to Firefox YouTube while Reaper is running, but with Pipewire-Jack integration this is a thing of the past. You can even route Firefox sounds to your DAW and record website music!