Chaining usb audio interfaces?

[Wengr]

Hello. I'm sure many of us have audio interfaces that output via usb. Provided that they also had the correct digital I/O, is it possible to chain them together in order to record simultaneously with a greater channel count?
For example - a two channel interface outputs via spdif, into another two channel interface, which then passes all four discreet channels to the computer via usb?

[Mbroady]

If I’m understanding you correctly, then yes

I have a similar set up, though I’m using FireWire instead of usb.

I have a Fireface UCX that I have connected to my PC and I’m using Calkwalk walk sonar as my recording platform. Hooked up via Spdif is an apogee Rosetta 200.
I can assign track inputs to either the Fireface or the Rosetta.

I use the Rosetta as the master clock

[FrankHudson]

At least with my example, yes.

I have an older Focusrite 8 analog channel USB interface connected at my studio into computer, and then upstream of that is an additional optically-connected Focusrite 8 analog channel expansion.

Wasn't hard to setup. Set the USB interface as the master word clock after hooking up the optical cable, and then all the channels on both interfaces appear in the DAW.


Chaining (well maybe more like "paralleling") two USB interfaces into two computer USB ports is apparently possible, but I've never done that. That doesn't seem to be what you're asking about though.

[Wengr]

Originally Posted by Mbroady

If I’m understanding you correctly, then yes

I have a similar set up, though I’m using FireWire instead of usb.

I have a Fireface UCX that I have connected to my PC and I’m using Calkwalk walk sonar as my recording platform. Hooked up via Spdif is an apogee Rosetta 200.
I can assign track inputs to either the Fireface or the Rosetta.

I use the Rosetta as the master clock

Thanks for the response. It makes me wonder how many channels one could have, or how many units one could chain, before we run out of usb or firewire bandwith? Obviously dependent upon the conversion settings, but still, can we know approximately how much at a given sample rate, without actually trying it?

[Mbroady]

Originally Posted by Wengr

Thanks for the response. It makes me wonder how many channels one could have, or how many units one could chain, before we run out of usb or firewire bandwith? Obviously dependent upon the conversion settings, but still, can we know approximately how much at a given sample rate, without actually trying it?

Probably more then I/we would ever need, assuming we do not have the philharmonic orchestra in our home studio

[MikeBmusic]

How many discrete 'output' channels via USB is the key to chaining - the last one in the chain (the one that outputs via USB to the computer) is the one that has to have the most. For example if it has 8 channel capacity, has 4 mic preamps and receives 4 channels vis SPDIF from another interface, that's it - 8 channels is the most its going to send to the computer. If you sendi8 channels to it via SPDIF, then you'd have to choose which 8 channels get sent out from the 12 available (8 SPDIF and 4 preamps).

[FrankHudson]

Originally Posted by MikeBmusic

How many discrete 'output' channels via USB is the key to chaining - the last one in the chain (the one that outputs via USB to the computer) is the one that has to have the most. For example if it has 8 channel capacity, has 4 mic preamps and receives 4 channels vis SPDIF from another interface, that's it - 8 channels is the most its going to send to the computer. If you sendi8 channels to it via SPDIF, then you'd have to choose which 8 channels get sent out from the 12 available (8 SPDIF and 4 preamps).

If I understand you correctly (and I may not..), I don't think that's correct. Are you saying that USB can only carry 12 channels, or is it a more specific limit in the use of the optical channels in a interface chained? In my example. The device connected to my computer is a Focusrite Scarlett 18i20 and then further in the chain from it is a Focusrite Scarlett OctoPre connected via ADAT optical cable to the 18i20.

As it happens, I haven't made much use of the optical inputs on these boxes other than the ADAT link, but I have used a fair number of the analog line and mic inputs. I'm not sure how many I've used at once in my largest recording project, but I may not have exceeded 12, though I currently have more than 12 connected for greatest flexibility in recording (i.e., I might play bass, keyboards, acoustic or electric guitar on a particular track or pass, they real keyboard player has two to three keyboards, and second guitar player, and vocals, etc.--and all are connected, and I just arm the tracks I'm going to use.) All the inputs appear to available in ProTools or Logic. Is there a "secret" limitation I'm not understanding or haven't encountered?

When I bought my 18i20 Firewire was an option, and there was a feeling that USB 2 couldn't cut it for serious track counts. I was surprised to see it offered for this model, and pleased over the years that it seems to work well.

[MikeBmusic]

Originally Posted by FrankHudson

If I understand you correctly (and I may not..), I don't think that's correct. Are you saying that USB can only carry 12 channels, or is it a more specific limit in the use of the optical channels in a interface chained? In my example. The device connected to my computer is a Focusrite Scarlett 18i20 and then further in the chain from it is a Focusrite Scarlett OctoPre connected via ADAT optical cable to the 18i20.

As it happens, I haven't made much use of the optical inputs on these boxes other than the ADAT link, but I have used a fair number of the analog line and mic inputs. I'm not sure how many I've used at once in my largest recording project, but I may not have exceeded 12, though I currently have more than 12 connected for greatest flexibility in recording (i.e., I might play bass, keyboards, acoustic or electric guitar on a particular track or pass, they real keyboard player has two to three keyboards, and second guitar player, and vocals, etc.--and all are connected, and I just arm the tracks I'm going to use.) All the inputs appear to available in ProTools or Logic. Is there a "secret" limitation I'm not understanding or haven't encountered?

When I bought my 18i20 Firewire was an option, and there was a feeling that USB 2 couldn't cut it for serious track counts. I was surprised to see it offered for this model, and pleased over the years that it seems to work well.

No, you misunderstood - the number of channels the final interface in the chain can carry via USB is the determining factor. USB2 (and 3) no longer is limited the way USB1 was.
As an example, the Focusrite Scarlett 18i8 has 4 XLR mic preamps + 4 line-in inputs + MIDI + SPDIF - but it's output via USB is limited to 8 discrete channels. YOu could have 4 mics and 4 line-in instruments/devices plugged into it, and record all those to separate tracks in your DAW.
Plug another interface into it via SPDIF, and you will have to decide WHICH 8 inputs to send to the 8 outputs.

[philjs]

Originally Posted by MikeBmusic

As an example, the Focusrite Scarlett 18i8 has 4 XLR mic preamps + 4 line-in inputs + MIDI + SPDIF - but it's output via USB is limited to 8 discrete channels. YOu could have 4 mics and 4 line-in instruments/devices plugged into it, and record all those to separate tracks in your DAW. Plug another interface into it via SPDIF, and you will have to decide WHICH 8 inputs to send to the 8 outputs.

That's not correct, Mike. The 18 in 18i8 is the maximum number of inputs that can be passed to a DAW, in this case 8 onboard, stereo SPDIF and up to 8 via ADAT. The number of outputs, 8 here, is the number of ouput returns from the DAW (not the inputs)...in other words two stereo pairs for the headphone outs, a stereo pair for the monitors and a stereo SPDIF out.

Phil

[MikeBmusic]

Originally Posted by philjs

That's not correct, Mike. The 18 in 18i8 is the maximum number of inputs that can be passed to a DAW, in this case 8 onboard, stereo SPDIF and up to 8 via ADAT. The number of outputs, 8 here, is the number of ouput returns from the DAW (not the inputs)...in other words two stereo pairs for the headphone outs, a stereo pair for the monitors and a stereo SPDIF out.

Phil

I must have misread the specs somewhere - manufacturers are purposely vague about the number of discrete channels their devices handle, you have to dig into the manuals.
In the case of the 18i8, it indeed will do 18 channels out via USB, but they are limited to 8 from the input jacks (4 mic + 4 line), 8 from the optical/ADAT inputs and 2 (just 'stereo') from the SPDIF inputs.
The end result is 'chaining' would only be effective if you wanted more mic preamps - then used that device's outputs to the line-ins (or just 2 mic preamps via SPDIF).

[KevWind]

humm interesting

[Mbroady]

Originally Posted by KevWind

humm interesting

That’s a bit cryptic. For someone who is a bit (no pun intended) limited in converter knowledge, can you elaborate.

[KevWind]

Originally Posted by Mbroady

That’s a bit cryptic. For someone who is a bit (no pun intended) limited in converter knowledge, can you elaborate.

Since I do not have a Focusrite I was interested in the discussion
And after going to the Focusrite website and opening the user manuals and finding the I/O charts in the manuals for both the 18i8 and the 18i20 It sure looked to me like the 18i8 while having 18 input channels could only actually output 8 discrete channels at any one time , where the 18i20 can output 20 which I assumed was why the model numbers the way they are. thus the 18i8 was 18 channels of input with 8 channels of output 18i (for inputs and - 8
for the outputs .......where the the 18i20 is 18 in and 20 out.

So with people saying that you could actually record 18 channels at once with the 18i8 I thought was pretty "interesting" , because it is not mentioned in the manual .......cryptic was not intentional .

[Mbroady]

Originally Posted by KevWind

Since I do not have a Focusrite I was interested in the discussion
And after going to the Focusrite website and opening the user manuals and finding the I/O charts in the manuals for both the 18i8 and the 18i20 It sure looked to me like the 18i8 while having 18 input channels could only actually output 8 discrete channels at any one time , where the 18i20 can output 20 which I assumed was why the model numbers the way they are. thus the 18i8 was 18 channels of input with 8 channels of output 18i (for inputs and - 8
for the outputs .......where the the 18i20 is 18 in and 20 out.

So with people saying that you could actually record 18 channels at once with the 18i8 I thought was pretty "interesting" , because it is not mentioned in the manual .......cryptic was not intentional .

Ahhh
You were referring to a specific post, and not the thread in general. got it
I asked because I find your knowledge base worthy of attention.

Thanks

[MikeBmusic]

Originally Posted by KevWind

Since I do not have a Focusrite I was interested in the discussion
And after going to the Focusrite website and opening the user manuals and finding the I/O charts in the manuals for both the 18i8 and the 18i20 It sure looked to me like the 18i8 while having 18 input channels could only actually output 8 discrete channels at any one time , where the 18i20 can output 20 which I assumed was why the model numbers the way they are. thus the 18i8 was 18 channels of input with 8 channels of output 18i (for inputs and - 8
for the outputs .......where the the 18i20 is 18 in and 20 out.

So with people saying that you could actually record 18 channels at once with the 18i8 I thought was pretty "interesting" , because it is not mentioned in the manual .......cryptic was not intentional .

The '8' in the part number refers to the number of AUDIO outputs - 6 + 2 SPDIF.