[LAU] Multiple sound cards

Len Ovens len at ovenwerks.net
Thu Jun 10 16:33:00 CEST 2021

On Thu, 10 Jun 2021, Alf Haakon Pietruszka Lund wrote:

> Hello list!
> I am on (K)Ubuntu Studio 20.04) and needed a couple of extra in- and 
> outputs, so I connected 2 USB audio interfaces to my computer (a 
> FocusRite Scarlett 2i4 and an Edirol UA-25ex - they're old, but reliable 
> devices).
> Through Studio Controls I set the Scarlett as master device and started 
> Jack, then I experienced recording and playback with Ardour in (as far 
> as I can hear) perfect sync.
> I was amazed at the ease of this setup and the problem-free routing of 
> audio signals, so just for testing I split a stereo source recording one 
> channel on each device to one stereo track in Ardour. To my ears, the 
> sync is still perfect.
> However, from this article 
> https://jackaudio.org/faq/multiple_devices.html it seems I have to 
> expect sync problems over time unless I do some manual configuring using 
> the alsa_in and alsa_out clients.

Studio-controls already does this for you except it uses zita-ajbridge 
instead of alsa_in/out for better quality and less cpu use.

However, I would still not split a stereo source over two devices. It is 
likely that the stereo image will wander some even though the two channels 
are "in sync". So long as there is some isolation between the two mics 
there should be no problem but a set of mics for one instrument (like a 
drumset for example) should all be on the same audio interface. So using 
more than one USB mic for podcasting should be fine. For recording a "live 
in the studio band" a single audio device or two connected with wordclock 
are still better.

In the end, often you use what you have and as it sounds good to you, that 
is what matters. A look to the future as equipment is replaced would see 
an audio device with a larger number of inputs and preamps.

Len Ovens

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