DSP Power

pkole · Post by **pkole** » Sun Jun 17, 2007 2:17 am

This is my first topic. I don't know if this has been discussed before but i'll give it a try.
I have a pulsar II (6 DSPs) and while trying to test it's limits i found out that when it was at high levels but did'nt crash, the project (at XTC mode in Nuendo) started clicks and pops.

So what i'd like to know is :
1. Is this what is supposed to happen? Because if this is normal then i will definetily feel disappointed.
2. If it's not, what i'm i doing wrong?

My pc setup is :
intel 6600 core2duo
intel motherboard
2 GB RAM
etc
I don't believe it is a pc problem.

Thanks in advance.
Panagiotis.

pkole · Post by **pkole** » Sun Jun 17, 2007 2:41 am

That was a quick response. Thanks.

These are good thoughts but :
I don't know what you mean by tuning my PCI.
I have no other PCI device
I was hoping that i would be able to load 3-4 synths and 7-8 fxs at the same time.

Adjusting latency, samplerate and the number of devices seems thonly solution.
Or maybe add a scope pro maybe

Thanks again for helping.

Lima · Post by **Lima** » Sun Jun 17, 2007 2:53 am

Adding more DSPs don't sort it out, imo, because the problem is probably related to the motherboard and not to the scope. The cards are supposed to work fine until the max dsp power is reached. If the demand is bigger then they stop working.

pkole · Post by **pkole** » Sun Jun 17, 2007 2:59 am

Do you mean that if i add a scope pro (14 DSPs) the power won't be 6+14=20DPs? What do you mean by telling that it's my motherboards problem?
I think that i will have more power. Please if you have time explain me what you mean and why my thought is wrong.

pkole · Post by **pkole** » Sun Jun 17, 2007 3:16 am

Thanks. I'll try it.

valis · Post by **valis** » Sun Jun 17, 2007 5:26 am

What was your ULLI when you had clicks & pops (ASIO latency)?

pkole · Post by **pkole** » Sun Jun 17, 2007 5:59 am

Well it was 3ms at 44.1Khz.

petal · Post by **petal** » Mon Jun 18, 2007 4:37 pm

Try to raise it to 4,7 or 13. My guess is that it will solve your problem with pops and cracks. If it doesn't then check the things that you have already been advised to by others.

valis · Post by **valis** » Mon Jun 18, 2007 5:59 pm

Yep agreed. This is typical when using DSP card effects as VST plugins, and is why many of us prefer to use the Scope user interface and deal with scope outboard of our sequencer. You'll find the same clicks & pops occur with UAD & Powercore btw...

pkole · Post by **pkole** » Tue Jun 19, 2007 12:36 am

Thanks guys.

@ petal : it's not always possible to record with 13ms latency. I record audio mainly.
@ valis : I totally agree, but scope interface is not always the editing-friendliest interface and i don't have an external interface. So it is really necessary for me sometimes.

Anyway, I believe i already solved the problem using a combination of your solutions.

valis · Post by **valis** » Tue Jun 19, 2007 1:02 am

I'm not necessarily trying to dissuade you from using XTC, just from thinking this is a limitation of Scope alone. The usual method for using Dsp based plugins is to use them for mixing workflows and not when 'tracking' audio where you might need low latency. If I worked in the tradional record/edit/mix workflow (I don't and most these days probably don't) and billed for studio time I might consider using Scope externally during recording (0-latency effects and routing) then switch to XTC mode for the mixing stage. WIth a modern PDC supporting host you'd get the benefits of both workflows.

The reason that you were experiencing pops is because each mono instance of a plugin that is dsp based uses 2 additional audio channels that you can think of as 'asio' channels, plus they introduce comparable latency for any tracks that are mixed in parallel in your host audio app. Meaning any tracks that go to the same busses & groups or have sends that are shared with the track you insert your plugin on. Add on a few more tracks with dsp inserts and a send or two and your internal host buffer goes way up and the number of audio channels is increased across the PCI bus dramatically. Eventually the cpu starts to chug when swapping between the large amount of data it has to shuffly around for the PCI bus and the host application both... A bit simplified but should give you a picture at least. For those of us that dealt with compensation manually before PDC was common the work the machine is doing is more obvious...

pkole · Post by **pkole** » Tue Jun 19, 2007 2:35 am

valis wrote:If I worked in the tradional record/edit/mix workflow (I don't and most these days probably don't) and billed for studio time I might consider using Scope externally during recording (0-latency effects and routing) then switch to XTC mode for the mixing stage. WIth a modern PDC supporting host you'd get the benefits of both workflows.

That was the conclusion i made out of all these.
I 'll try to find a way to work it out because i mainly want to make music but sometimes we have to understand situations like these to be able to make music.

I will inform about the results.

Thanks everyone for the support.