[ardour-users] 48 channels on ardour

John Emmas johne53 at tiscali.co.uk
Wed Jul 18 00:39:56 PDT 2007


Thanks guys, I appreciate the advice.

Thomas, you said something that confused me....

>
> 2 HDs would be better, one for recording to, one for playback,
>
This doesn't make sense to me.  Surely you'd have to play the audio back
from the same drive that it was recorded on - or would you copy the audio
from the record drive to the playback drive after it's recorded?

Thanks,


John

----- Original Message ----- 
From: "Thomas Vecchione" <seablaede at gmail.com>
To: "John Emmas" <johne53 at tiscali.co.uk>
Cc: <ardour-users at lists.ardour.org>
Sent: 18 July 2007 05:46
Subject: Re: [ardour-users] 48 channels on ardour


> 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;)
>
>         Seablade
>
> 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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