[ardour-dev] Where to go digital

philicorda philicorda at ntlworld.com
Mon Mar 6 08:22:33 PST 2006

On Mon, 2006-03-06 at 12:53 +0000, Iain Kennedy wrote:
> Hi,
> We use ardour for a mobile internet radio station and are gradually 
> growing our studio. We have been getting by with a small mixing desk and 
> an RME multiface, but as we are doing stuff with multiple microphones and 
> live bands, we need a more capable mixer with sub-mixes etc to improve our 
> monitoring situation.
> We have two basic choices of where to spend our budget
> a) A nice analogue mixer with subgroups
> b) Using ardour (and a MIDI worksurface) to do all the mixing/submixing 
> etc.
> Due to the often raucous nature of our studio, we currently use channel 
> inserts with limiters on the microphones. If we were to buy some 
> microphone preamps (such as RME's Octamic D), we'd like to use the digital 
> connection to get the audio into Ardour via the Multiface, and still keep 
> as many analogue connections spare as possible for live instruments etc.
> Would using a LADSPA digital limiter give us similar control over the 
> signal, or are we likely to run into the situation where we have a clipped 
> signal entering into the system? My knowledge of audio falls somewhat 
> short of the mark when it comes to the analogue to digital domain.

No. The limiter has to be before the a/d converter to prevent clipping,
so the signal will already be clipped before it gets to the ladspa
limiter plugin.

Luckily, the Octamic looks pretty quiet so you can leave lots of safety
headroom without worrying about noise. Recording at 24bit helps here

I used to try and get a hot signal into the a/ds all the time, and use
analog compressors/limiters for protection. After a while I found
leaving more headroom does not add significant noise when it comes to

One caveat though... I find using a computer to set up the monitoring
mixes is a real pain, due to latency and the lack of fast control from
using a mouse compared to a desk. (It only needs to be a few ms latency
to cause phase problems in headphones). It gets real complicated when
you need to set up multiple monitor mixes with eqs on them too.

What's your desk like? If it has ok pres then you could take 16 or so
direct outs from the channel inserts to the a/d converters, and get
cheaper converters than the RME (ones without mic pres). Then the desk
is just for monitoring.  You could also still use the limiters in-line
between the desk and the converters if you are worried about clipping. 

You don't really need subgroups for setting up monitor mixes, if your
desk is just for monitoring and has a few aux sends then these work
fine. (aux busses are essentially subgroups anyway.)

> We've done a reasonable amount of investigation up to this point, but it's 
> fairly crucial that we make the right decision, so any help you have to 
> offer would be greatly appreciated.
> Regards,
> Iain
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