[LAU] synchronization of two RME MADI cards

[Giso Grimm]

On 13.11.19 21:59, Len Ovens wrote:
> On Wed, 13 Nov 2019, Giso Grimm wrote:
> 
>> Dear linux-multichannel-audio-users,
>>
>> we are running a setup with two RME MADI cards to drive a system with
>> approx. 100 playback channels. We are using jack2 and zita-j2a to
>> achieve a sufficient number of playback channels. The sample clocks are
> 
>> On a similar setup (with two different card types) I noticed that the
>> latency between the cards is fixed as long as jack/zita-j2a is running,
>> however, the latency differs between starts of jack. This seems also be
>> the case in the setup with two MADI cards.
> 
> USB cards by chance? This is a known problem with USB Audio. Well
> actually with USB in general. I am coming to the realization USB audio
> devices are not desirable for profesional audio. They are sort of the
> best one can get on a limited (reasonable?) budget. It is unfortunate
> that USB has become the way periferals are added on modern computers
> when it comes to audio. USB is great for many other things from printers
> to mice, but not really critical audio.

no, PCIe (and RME MADI hdspe cards are far from being budget - although
quite cheep compared to over 100 loudspeakers and corresponding
DA-converters :-) ). Sample clock sync works perfectly.

The only response I got from RME is "it works on Windows without any
latency differences" - however if I understand it correctly in this case
the interrupts of the two sound cards need to be somehow synchronized
with sub-sample precision.

> 
> 
> 
> -- 
> Len Ovens
> www.ovenwerks.net
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