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Axe III USB bandwidth question

SeanOneil

Regular
When I use my AxeIIXL+ as a PC audio interface I run into bandwidth issues vs. my outboard Firewire interface. When I get my track count very high I'll get stuttering, skipping and other issues forcing me back to my outboard Firewire. The PC is not the bottleneck, everything is run on 100% SSD drives and the CPU/Disk I/O meters are barely off the floor when I use Firewire.

Is the USB I/O in the Axe III going to do anything to improve performance in this area or is it still a USB 2.0 based I/O?

Thank you,
 

Smittefar

Fractal Fanatic
This has nothing to do with the USB bandwidth. It sounds like you need to increase the buffer size on your AxeFX when using it as an audio device.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
The effective throughput of USB 2.0 is roughly 280 Mb/s. One channel of audio is 48000 samples/s * 24 bits/sample = 1.152 Mb/s. Theoretically you could transfer over 200 channels of audio on USB 2.0. Whatever issue you are experiencing has nothing to do with the "bandwidth" of USB.

That said I've tested the Axe-Fx III driver and I can set the buffer all the way down to 8 samples with no issues.
 

SeanOneil

Regular
Thanks guys, but I've set my buffers all the way up to the max and still have issues with skipping in high track count projects. FYI I have several projects with track count in the hundreds so that's probably the issue. Also as I mentioned I do not have the issue with Firewire connection using the same buffer sizes.
 

Owczar

Regular
It's about driver. For example with my little rme babyface (which is running on USB 2.0 too but rme have great drivers) I can run my session with lot of virtual instruments and plugins with 96 buffer fluently. With XL+ I need to set it to 256, overthwise it's crackles and dropouts all the time. It's more or less the same on Mac and PC.
 

chris

Legend!
Thanks guys, but I've set my buffers all the way up to the max and still have issues with skipping in high track count projects. FYI I have several projects with track count in the hundreds so that's probably the issue. Also as I mentioned I do not have the issue with Firewire connection using the same buffer sizes.
What does track count have to do with the Axe and USB? It process the same amount of I/O regardless right?
 

SeanOneil

Regular
I don't know. The only thing I do know is that when I start a blank project with the Axe as audio interface it works fine, everything is fast and reliable. When the number of audio tracks gets very high things start to choke up. Increasing the buffer size helps but when I add more tracks eventually the same thing happens again. I've had other USB audio interfaces and they seem to do about the same as the Axe, whereas the Firewire interfaces I've used did not have the same issues. That's what led me to believe it's probably bandwidth related somehow. I was hoping for a Firewire port on the Axe III but no biggie because I know it's not intended as an audio interface first and foremost and it works just fine for most people because they don't have ridiculous track counts. :)
 

chris

Legend!
I still don’t see what track count has to do with anything when the Axe processes 2 stereo outs and ins regardless of track count. Weird.
 

yeky83

Veteran
What does track count have to do with the Axe and USB? It process the same amount of I/O regardless right?
Track count matters cus USB audio drivers use CPU. As CPU tries to process all the tracks, it's working harder and doesn't have time for the Axe-Fx USB audio driver's demand.

I don't know. The only thing I do know is that when I start a blank project with the Axe as audio interface it works fine, everything is fast and reliable. When the number of audio tracks gets very high things start to choke up. Increasing the buffer size helps but when I add more tracks eventually the same thing happens again. I've had other USB audio interfaces and they seem to do about the same as the Axe, whereas the Firewire interfaces I've used did not have the same issues. That's what led me to believe it's probably bandwidth related somehow. I was hoping for a Firewire port on the Axe III but no biggie because I know it's not intended as an audio interface first and foremost and it works just fine for most people because they don't have ridiculous track counts. :)
Yeah, like @yek said, if you're getting the same issue with other USB audio interfaces, it's your computer not being able to handle the track count + USB audio processing. Bigger buffer should help greatly, but if that's not helping you, no other real solution than a better computer... for now, you can search for stuff like "how to optimize PC for audio interface" and try what those guides suggest (turning off Windows visual effects, CPU throttling, etc.), should help a bit.

(FireWire is a more stable protocol for audio vs USB, so you're not getting these issues with it.)
 
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steadystate

Fractal Fanatic
That said I've tested the Axe-Fx III driver and I can set the buffer all the way down to 8 samples with no issues.
That is an insanely small buffer. I've never heard of such a thing. I hope you would consider making small buffer sizes like 8, 16, and 32 available to the user, even if many systems choke. For some, it's a major selling point for virtual instruments/drums. And I thought 32 samples was impressive.
 
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so, USB is designed to use software running on the computer’s CPU, whereas firewire/thunderbolt uses a dedicated hardware chip. this means a USB interface will always have slightly higher CPU useage than a firewire/thunderbolt interface.*

This is an intentional design decision by Intel to make USB cheaper to implement than firewire/thunderbolt.**

that said, if you’re running enough tracks in your DAW that you run out of CPU, it’s probably cheaper to get a faster computer than to buy a firewire/thunderbolt interface.

*this is why the current fractal gear cpu usage goes up a couple % when you connect it to your computer, and is one (i’m guessing) of the reasons cliff put a separate chip to run the DSP and USB/MIDI stuff in the III

** this is most likely why there’s no firewire/thunderbolt in the III - despite there no longer being a license fee, there would need to be a dedicated piece of hardware in the unit, driving up the price and creating future support nightmares
 
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ChristThePhone

Fractal Fanatic
...
This is an intentional design decision by Intel to make USB cheaper to implement than firewire/thunderbolt.**
...
No, the USB architecture is about 20 years old now. It was state of the art back then. Don't forget it started as a replacement for RS232 and PS/2 connections on the PC with low bandwidth requirements. And yes, it had to be sufficiently cheap too.
 
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