Delay compensation when mixing 100% OTB

[el biciclista]

I am mixing out-of-the-box (OTB) with HD2 system:
-16 tracks each separately go --> 192 digital I/O --> Lavry Blue DAC's --> hardware compressor --> hardware EQ --> hardware summer/mixer (Neve 8816)
-The individual track Direct Outs from the Neve fader pack (8804) (after processing) go to a patchbay where they are patched to hardware effects (reverbs/delays/etc.), which are then summed in two Chandler mini mixers
-The stereo mix from the three summing units goes --> compressor --> EQ --> 1/2" tape deck (ATR-102).
-The stereo mix on tape is then played back --> Lavry Blue ADC --> 192 digital I/O --> print in the Pro Tools HD session.

So, all the processing is with hardware, and I normally am not using any plug-ins.

I have delay compensation switched off.

Am I correct that delay compensation is not useful in this situation, since the delay thru outboard gear is negligible?

My system is HD2, PT 7.2, OS 10.4.6, PowerMac G5 Dual 2.7.

[PTUser NYC]

Am I correct that delay compensation is not useful in this situation, since the delay thru outboard gear is negligible?

Yes. The only real latency in your situation is the D/A and the A/D - in both cases all tracks are being treated to the same trip, so they will stay aligned.

[danms66]

Conversely, It wouldn't really matter if you turned it on.

[el biciclista]

Yes. The only real latency in your situation is the D/A and the A/D - in both cases all tracks are being treated to the same trip, so they will stay aligned.

Terrific, excellent outcome.
Thanks.

[25ghosts]

the only way to be 100% sure is to record the signal that you are processing only with the processor set to bypass. Lets say it's a vocal line - now after recording the "processed" signal put it on a track below the original - Now blow up the zoom and check the start points - if they are 100% identical then you need NO ADC if not - well then you do need it. you coul also phase invert the original or the processed and pan them L-R to see if they cancel out in mono. If a delay has occured while recording then the signal wont cancel out. later when you apply the processer to the signal it wont cancel out of course as the signals are no longer identical.

[PTUser NYC]

Sorry 25ghosts, that isn't it.

Clearly the audio coming back into Pro Tools is going to be VERY late from the source tracks. Even if all you were doing was bouncing through that tape deck. The head gap on an old Ampex machine at 15ips was something like 124ms - clearly significant.

The question, as I understood it, was whether or not to worry about the difference in latency between the various analog paths that the stems take. If there was appreciable latency in analog processing, we would have been running into it in the days of consoles.

The answer to the question is: All the tracks will be very late from their origin, but they will all be late by the same amount.

[el biciclista]

Yes, I agree.

I normally monitor the mix during mixdown after the mix bus, but before going to tape. I can patch this back into Pro Tools and print the mix, and when I do this I find negligible latency thru all the analog gear.

Once I'm happy with the mix, I then patch the mix to the tape deck and record it to tape.

Then I rewind the tape and play it back into Pro Tools and print it to a stereo track................so there is about 5 minutes of "coffee break latency" thru the tape deck! (smile).

[PTUser NYC]

I can patch this back into Pro Tools and print the mix, and when I do this I find negligible latency thru all the analog gear.

Well the trip through the converters and back in going to cost a few milliseconds of latency, so if the position of the mix relative to the source tracks is important to you, then using ADC would provide a benefit.

The only place it doesn't matter is between the tracks that go to your analog submixer, and any additional analog trips from the aux sends in your submixer. Obviously these have such low latency that the effect (no pun intended) is negligible.

Of course this was always true back in the day when we used consoles and tape machines, and even if the delay there was a problem (and it isn't) using ADC wouldn't help anyway.

[el biciclista]

Well the trip through the converters and back is going to cost a few milliseconds of latency, so if the position of the mix relative to the source tracks is important to you, then using ADC would provide a benefit.

That's not really an issue. If for some reason I want to have it perfectly aligned with the original tracks to, say locate a problem I'm hearing in the mix, I can just nudge the mix track a smidgeon. On these rare occasions, that is much easier than fooling around with delay compensation.

Thanks for the help.

[Danny Caccavo]

You should be able to use delay compensation with a large outboard chain - it will compensate for the delay so that the processed track will line up with the other tracks. It shouldn't be necessary for you to render that processing to a track.

That being said, if there is any situation that is showing up for any of you that seems like a reproducible bug, we are VERY interested in fixing the problem or problems. Please us know if you would be willing to send us a session - the session does not have to have audio - you just need to tell us what tracks we should put audio on.

Much obliged...

Danny Caccavo
Product Manager
Digidesign