Pro Tools 10 ADC

[Chinagraf]

What's the dealio? I'm trying out PT10. I've setup hardware inserts which was incredibly simple, then I setup delay compensation and it still phases. So then I have to go to the 'H/W insert delay' page and add a delay of 80 samples to get it sitting right after recording with and without HW to work out the sample delay.
Am I doing something wrong? I use Cubase 7 and all you do is click a button once to ping the hardware and it works instantly. I've matched the buffer settings for my converters in the delay compensation settings.
I'm running SSL's on MADI. The system is Win 7 64 with 24 gig ram.
Am I missing a step or something, or is Protools on a PC just some sort of non event? I'd like to be able to have it here as an option when people have stuff already tracked in Tools, but hmmmm..?
Thanks...

[Drumstruck]

We would probably market that as a "special feature" ....... if you go to 256GB RAM and 48 cores it may be better

[peat]

Page 990:

http://www.avid.com/static/resources/co ... _Guide.pdf

[Chinagraf]

Hi, yeah, I've done pretty much what is says, I'm just a bit surprised you have to record with and without the hardware then zoom in and measure etc. I would have thought the system would be able to work that out itself.

[peat]

It would be nice,

Guess it just means you only have yourself to blame if you get some phasing really.

I always thought there may be some discrepancy with this any way as the offset is input as a time value as opposed to a sample value. Obviously this is done to be able to change sample rates, yet still maintain the same value in the offset.

However, perhaps a unit doesn't give a round trip latency that is a division of 10 microseconds.

Using Avid/Digidesign hardware is another story as this offset is automatically calculated.

[Chinagraf]

Using Avid/Digidesign hardware is another story as this offset is automatically calculated.

Ha! Why doesn't that surprise me?

[Sammas]

Isn't the delay set in milliseconds, rather than samples?
...as stupid as that sounds.

Has anyone actually managed to do stuff like parallel bus compression using a hardware compressor in Protools HD?

The internet seems to suggest it won't happen due to sub-sample latency that occurs yet can't be corrected, so there will always be a small amount of phasing occurring. My experiences have been like this, but (perhaps with dubious optimism) it might be caused by the apogee conversion I am using.

[peat]

Yes the H/W insert delay is a value given in time, not samples.
Not stupid at all as if it were given in samples, and you changed sample rate, it would not match anymore.

I routinely use hardware inserts and intricate parallel processing techniques with Pro Tools HD and a non Avid/Digidesign interface (Lynx) and have no problems at all.

For reference, the round trip time of my Lynx AES card and Aurora converter is 0.60ms

[Sammas]

In... ter... west... ing! Thanks Pete! I'll have to investigate it further.

[gigpiglet]

if you are talking sub sample accuracy.
is it really something thats a problem?
like... i dont know. maybe i dont listen like you guys do
but less than a sample?
unless you are deliberately summing an in and out of phase signal at unity.
are you going to hear any difference at all?

sorry if that offends anyone....

[peat]

I guess it's more of a cumulative thing really.
When you have one source reaching an output through many different paths, and combining with other sources on the way there.
But to be honest I've never stopped playback and thought, damn there is a 1 microsecond delay going on somewhere.

However I can definitely hear a (positive) difference when similar processing is done in an analogue system (console busses etc..)

[Sammas]

if you are talking sub sample accuracy.
is it really something thats a problem?
like... i dont know. maybe i dont listen like you guys do
but less than a sample?
unless you are deliberately summing an in and out of phase signal at unity.
are you going to hear any difference at all?

sorry if that offends anyone....

No offense taken at all, Gareth. The problem I hear is very apparent to the point that I don't think its just a case of being less than a sample out. I read comments about the less than sample latency and just dismissed it and got on with making music as you suggested. There are simply ways around it when it becomes too apparent.


Half a sample out of phase at 44.1khz would mean -6dB @ 20khz... I think. If I can wrap my head around it. That is likely the worst case scenario with Avid HD & 192 interfaces, and Lynx auroras which were conveniently designed to mimic the latency HD and 192 interfaces when using the HD card.

Apogee 16x's on the other hand... They rely on using the offsets that you manually set in protools based on the sample rate you are using. The kicker is, its set in milliseconds with the smallest division being a tenth of a ms. 0.1 x 44.1 = just over 4 samples... but I guess that with 4 samples being the smallest denomination, that gives an error of 2 samples (either 2 samples early, or 2 samples late). That starts phasing at around 11khz.

[gigpiglet]

interesting maths mate....

im on lynx auroras
and the point you mention was one of the "selling points" when i decided to go that way.
i didn't research it/ do the maths as you have... but it seems like a valid point!

having said that.
i dont use hardware inserts.
cause i have a big analogue console! and use PT more like a fancy tape machine.

but today... im lacquering the floors.
so no audio at all.
thats the life hey!

[petermulas]

i often wondered if it is worth manually correcting for inherent latency from the outboard gear itself, especially analogue units.

obviously the latency for the round trip is vital however prior to in the box mixing the latency from an outboard unit was never compensated for (not that you would be able to do it easily) and yet a lot of amazing mixes were completed using all types of parallel processing.

why is it of such importance now? it is just because we can?

[Chinagraf]

I don't think people worry about that, I know I don't. Doesn't voltage travel down cables at the speed of light or there abouts? The only thing I occasionally wonder about is outboard that has conversion involved, like a digital reverb or a delay, but then I'm not using those in parallel, and all my comps are analog through the full signal path.
My pcm42 has a conversion delay, my reverb units do too but as you say, we never worried about that when it was on the send or insert of an analog console. I just go with that philosophy. Set the delay comp for the round trip of my daw converters and leave it at that.

[Sammas]

Audio propagates through an analogue circuit at close to the speed of light. There is essentially no latency. Someone on this forum taught me that.

The latency is part of the AD and DA conversion, plus sample buffers, etc within digital processing. I suspect latency have never been a problem with digital outboard gear as its generally used for time-based effects anyway. A 2ms latency on a reverb processor will just result in 2ms of additional pre-delay.

[petermulas]

I don't think people worry about that, I know I don't. Doesn't voltage travel down cables at the speed of light or there abouts? The only thing I occasionally wonder about is outboard that has conversion involved, like a digital reverb or a delay, but then I'm not using those in parallel, and all my comps are analog through the full signal path.
My pcm42 has a conversion delay, my reverb units do too but as you say, we never worried about that when it was on the send or insert of an analog console. I just go with that philosophy. Set the delay comp for the round trip of my daw converters and leave it at that.

i only bring this up because when receiving pro tools classes a few years back compensating for outboard gear was the specific reason the trainer suggested we use the function for. this trainer wasn't your garden variety audio college trainer either, he was head of full sail for a number of years and manager of avid's asia/pacific division.

[Chinagraf]

Was he talking about outboard gear with a conversion stage, or outboard with a fully analog path? If he's was talking about outboard with conversion stages I can see where he was coming from but most of the time it won't matter. If it was gear with a fully analog path, then I disagree.

I guess also perfect design theory and working professional practice don't always meet exactly. Like Nath said, a 1- 2 msec conversion delay is going to make little difference with a time based effect that isn't used in parallel. To the contrary, the example I mentioned of a PCM42, the slight conversion delay is something people have used for years to create wide guitar sounds - set the delay time to zero, hit the input really hard so it gets limited and pan the dry signal left and the delay return right. Humungous (sp?) So in theory what is a flaw according to a designer is actually working for you.
I think that's where working experience in a studio mixing day in day out for years trumps heading up any company or institution as far as theory versus prac. Not talking about me in particular, but just in general. In the lab/classroom I figure the emphasis is on what is mathmatically/physically/electronically/etc correct. In the studio all that matters is does it sound good?

[Sammas]

I don't think people worry about that, I know I don't. Doesn't voltage travel down cables at the speed of light or there abouts? The only thing I occasionally wonder about is outboard that has conversion involved, like a digital reverb or a delay, but then I'm not using those in parallel, and all my comps are analog through the full signal path.
My pcm42 has a conversion delay, my reverb units do too but as you say, we never worried about that when it was on the send or insert of an analog console. I just go with that philosophy. Set the delay comp for the round trip of my daw converters and leave it at that.

i only bring this up because when receiving pro tools classes a few years back compensating for outboard gear was the specific reason the trainer suggested we use the function for. this trainer wasn't your garden variety audio college trainer either, he was head of full sail for a number of years and manager of avid's asia/pacific division.

The trainer is correct, but the delay itself isn't attributed to the analogue outboard gear specifically.
It is attributed to the digital to analogue and analogue to digital conversion processes. This is why there is no need to compensate for latency when working entirely in the analogue domain.

[waitup]

Nath,

I'm pretty sure Peter understands that the most significant attributer to the delay we're compensating for is the delay caused by digital to analogue and analogue to digital conversion. I think he's pointing out that this Pro Tools trainer (and I'm pretty sure he's talking about Andy Hagerman?) suggests that the analogue device in the loop contributes to the delay as well.

I got in to a bit of an argument with Andy about this when I was doing similar training earlier this year. I've never seen an analogue device cause a delay that would result in audible issues, or even measurable ones, with the exception of SOME compressors doing MASSIVE amounts of gain reduction.

That said I'm happy to be proven wrong!!

Nick.

I don't think people worry about that, I know I don't. Doesn't voltage travel down cables at the speed of light or there abouts? The only thing I occasionally wonder about is outboard that has conversion involved, like a digital reverb or a delay, but then I'm not using those in parallel, and all my comps are analog through the full signal path.
My pcm42 has a conversion delay, my reverb units do too but as you say, we never worried about that when it was on the send or insert of an analog console. I just go with that philosophy. Set the delay comp for the round trip of my daw converters and leave it at that.

i only bring this up because when receiving pro tools classes a few years back compensating for outboard gear was the specific reason the trainer suggested we use the function for. this trainer wasn't your garden variety audio college trainer either, he was head of full sail for a number of years and manager of avid's asia/pacific division.

The trainer is correct, but the delay itself isn't attributed to the analogue outboard gear specifically.
It is attributed to the digital to analogue and analogue to digital conversion processes. This is why there is no need to compensate for latency when working entirely in the analogue domain.

[Chinagraf]

Maybe the trainer that mentioned it has really long patch cords. You may induce a delay of about a millisecond if your cables in and out of the analog device were each 93 miles long.

[mylesgm]

if your cables in and out of the analog device were each 93 miles long.

That'd be one hell of control room... but you could set up some sweet toy train sets to pass messages back and forth to chaps on the other sides of the 'room'. Manning would probably make his out of ducks.

[Sammas]

Nath,

I'm pretty sure Peter understands that the most significant attributer to the delay we're compensating for is the delay caused by digital to analogue and analogue to digital conversion. I think he's pointing out that this Pro Tools trainer (and I'm pretty sure he's talking about Andy Hagerman?) suggests that the analogue device in the loop contributes to the delay as well.

I got in to a bit of an argument with Andy about this when I was doing similar training earlier this year. I've never seen an analogue device cause a delay that would result in audible issues, or even measurable ones, with the exception of SOME compressors doing MASSIVE amounts of gain reduction.

That said I'm happy to be proven wrong!!

Nick.

Whoops! My apologies... assumption is the mother of all f&%k ups as they say. I was just thinking how ambiguous the phrase "you have to compensate for the delay when inserting analogue hardware into your protools session" is.

It is pretty sad indeed is Avid’s training and education manager for the whole of Asia can't get it right.

[Mark Bassett]

sub-sample phase shift hey.

Can someone explain to me how you can have have two signals in the digital domain, one of which is 1/2 a sample out of phase with the other one?

Or have I missed the point entirely.

Half a sample out of phase at 44.1khz would mean -6dB @ 20khz...

A single sample delay introduces the first cancellation at the Nyquist frequency (22050Hz @44.1kHz).

However, to my knowledge you cannot have a signal that is half a sample out of time in the digital domain and if you're combining analogue signals, there are no samples.

If you're talking about combing two analogue signals with a phase delay equivalent to the sample period at an (arbitrary) sample rate, that's a different story.

[Sammas]

sub-sample phase shift hey.

Can someone explain to me how you can have have two signals in the digital domain, one of which is 1/2 a sample out of phase with the other one?

Or have I missed the point entirely.

Two signals in the digital domain, of which one is outputted to analogue then resampled back to digital and "automatically" aligned by whole sample increments.

[Mark Bassett]

Cheers Nath.

So if you're at 44.1kHz sample rate and you have a half sample delay, introduced by the situation you described, combing your two signals will introduce the first cancellation frequency at 44.1kHz, not 20kHz.

Not only can't you hear that high up, it's higher than the Nyquist frequency, so everything anywhere that frequency has been already removed on the way back through your A/D's anti-alias filter.

If you're working above 44.1kHz, it's less of a problem, if that's even possible.

if you are talking sub sample accuracy. is it really something thats a problem?

Nope, it's inaudible.

If you can hear it, well, you can't, not because you're not batman, but because the frequencies it would affect aren't in you mix anyway

I read comments about the less than sample latency and just dismissed it and got on with making music as you suggested.

. Good man.

[Sammas]

That strangely makes sense to my flu riddled brain. It still doesn't paint such a pretty picture for people using non-avid interfaces (apogee 16x for example) where you can only manually compensate for latency via tenth of a millisecond increments.

[Manning]

Manning would probably make his out of ducks.

duckamps.JPG