[ardour-users] 48 channels on ardour

Thomas Vecchione seablaede at gmail.com
Tue Jul 17 22:46:56 PDT 2007

Well I can tell you what I am running.

Currently:(Hopefully to be upgraded soon) a

1.6 GHz Opteron N-Force 4 Chipset(One of the few that didn't have problems
with PCI-E and audio)
1 Gig of Ram.
RME HDSP 9632 Interface
GeForce 6600 PCI-E
Assorted HDs(All 7200 RPM):
   1 200 gig system drive SATA
   1 200 gig playback(At the moment) IDE
   And whatever else I might dig up as the need arises;)

As you can see, my computer is not that much larger spec'd than  yours.
What primarily is going to make the difference is having a decent set up
system (On Linux a Realtime Kernel etc.) and HD availiability.  Running
Playback/Record/ and your System off one HD will kill your performance VERY
fast.  Try to get your System on One HD and your audio on another as a
minimum, 2 HDs would be better, one for recording to, one for playback, if
you do tracking a lot.  RAID arrays aren't really a bad idea either if you
have the drives, though obviously, as you can see from my specs, not
absolutely necessary.

If you are in Ardour, if the problem is your HD performance, it will tell
you.  A warning message will pop up saying your HD was unable to keep up.
If your problem is xruns(dropouts) and playback continues, chances are your
problem could be solved by ensuring you have realtime capabilities as that
user, as otherwise what can happen is an interrupt triggered by other
software will override your audio, and then you will drain your buffer
before your audio gets a chance to work again.  That is what realtime
preemption helps with, your audio card and software will preempt other
software as needed.  Or at least that is my understanding;)


On 7/17/07, John Emmas <johne53 at tiscali.co.uk> wrote:
> I'd be interested to know what hardware you guys are running to get
> 24 & 48 channels.  To be honest, my copy of Ardour often struggles to
> play just 4 channels simultaneously.
> "Struggles" is probably an exaggeration but I do get occasional glitches
> such as a short 'hole' in the sound or an occasional 'skip'.  I've never
> timed how often these happen but I doubt that I could replay 10 whole
> minutes of audio without encountering at least 1 glitch.
> My hardware is pretty old but not unrespectable.  I have a 1.2GHz Athlon
> with 512MB of RAM, but my disks are just standard EIDE types (though
> reasonably fast).  I'm running OpenSuse 10.2 with Jacklab and an RME
> HDSP9632 sound card.  Enough to run 4 x simultaneous channels without
> encountering problems, I'd have thought.  Maybe I need to tweak
> something??
> Just out of interest, what is considered a 'minimum spec' for say, a 24
> channel system?
> John
> ----- Original Message -----
> From: "John Rigg" <au at sound-man.co.uk>
> To: "Kevin Cosgrove" <kevinc at doink.com>
> Cc: <ardour-users at lists.ardour.org>
> Sent: 17 July 2007 23:04
> Subject: Re: [ardour-users] 48 channels on ardour
> > On Tue, Jul 17, 2007 at 02:17:44PM -0700, Kevin Cosgrove wrote:
> >>
> >> On 17 July 2007 at 20:04, John Rigg <au at sound-man.co.uk> wrote:
> >>
> >> > Yep. You'd have to decide if you really need to use 96kHz rather
> >> > than 48kHz. With something like a Delta 1010, most of the potential
> >> > increase in quality at 96kHz is wiped out by the increased clock
> >> > jitter, so it isn't really worth using more than 48kHz with that
> >> > particular hardware.
> >>
> >> Very interesting.  Is there much additional jitter from trying to
> >> sync multiple units, or is the internal jitter of one unit enough to
> >> degrade the quality?  How are you determining the quality differences
> >> between 48kHz and 96kHz?  Are you looking at the noise floor?  Or,
> >> maybe you've run a test like "effective bits"?  See
> >>
> http://www2.tek.com/cmswpt/tidetails.lotr?ct=TI&cs=Application+Note&ci=4405&lc=EN&from=rss
> >
> > I haven't done extensive comparisons between 48kHz and 96kHz,
> > but I didn't hear enough of a difference between them to justify
> > doubling the disk bandwidth and space.
> >
> > The Delta 1010 does have a jittery clock implementation. That's what
> > happens when the clock is on the PCI card and the converters are at
> > the other end of a 3m cable, with HF losses and crosstalk with all
> > the other signals in the cable contributing to jitter. I got a
> > noticeable improvement in audio quality just by replacing the 3m
> > host cables with 1m ones.
> >
> > Regarding jitter when syncing, the 1010s sound better when using
> internal
> > clock than when synced via either BNC or S/PDIF. If I don't need more
> > than eight channels (eg. when overdubbing) I run jackd with only one
> > Delta 1010, set to internal clock. This situation can't be completely
> > remedied by using a high quality external clock, because jitter occurs
> > in the cable and the Delta 1010 hasn't got very good jitter attenuation
> > on its S/PDIF or wordclock inputs. It can be minimised by syncing with
> > very short, well-shielded cables with low capacitance.
> >
> >>
> >> > Yes. At least one user on these lists is using it for 64 channels.
> >> > I'm currently using three Delta 1010s for 24 tracks. It's reliable
> >> > and I don't get xruns (I use large period size and monitor from the
> >> > 1010s' hardware outputs for `zero latency' monitoring though). Having
> >> > said that,
> >>
> >> Are you sync'ing your three via the BNC sync connectors or through
> >> the S/PDIFs?
> >
> > When using all three 1010s I clock them from an Audiophile 2496 card
> > (also ice1712) in the same box, via a home-made 3-way S/PDIF splitter.
> > That way all three 1010s receive their clock signals at the same time.
> > As a bonus the 2496 also bumps the 1010s off the IRQ that is shared by
> the
> > graphics and network adaptors onto individual IRQs of their own. I'm not
> > using the 2496 for I/O in this configuration.
> >
> > This is getting a little OT, but feel free to email me off list if you
> > have more 1010-specific questions.
> >
> > John
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