[ardour-users] 48 channels on ardour

[John Emmas]

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
> _______________________________________________
> ardour-users mailing list
> ardour-users at lists.ardour.org
> http://lists.ardour.org/listinfo.cgi/ardour-users-ardour.org