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  #1  
Old 09-02-2018, 07:10 AM
dvdr dvdr is offline
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Default Latency issue (analog outboard gear on RME Fireface UFX II / PT 2018.7)

Hi

I am making my first steps with analog outboard gear. So first, I have read a lot about latency and the ADC option in ProTools. Still, I am running into issues.

This is the system: PT 2018.7, RME Fireface UFX II, RME Fireface 800 (latter connected via ADAT to the UFX II as a "channel expansion").
Analog outboard gear is connected directly to the UFX II (currently a compressor, an EQ and a summing amplifier), and can easily be used as an insert, on a send or as I/O. So my routing is fine.

Automatic Delay Compensation in PT is turned on (I can see the ADC symbol - it stays green all the time - but I am still running into latency issues: comb filter effects, phasing issues etc. and an additional 25ms delay, when printing tracks to a stereo track inside the session (@88.2 kHz).

To test the issue, I have copied a stereo test track to a second track and play both back simultaneously.

a.) no outboard gear inserted: no audible issues, just a higher level in the master track, as it's supposed to be, when two identical signals are combined.
b.) outboard gear as an insert in the second track: phasing and comb filter effects.
c.) outboard gear as a send in the second track: phasing and comb filter effects.
d.) outboard gear as an output in the second track: phasing and comb filter effects.

I then tested the latency of this "outboard route" by simultaneously recording track 1 to a new track and track 2 to another new track, using the different outboard "positions" as insert, send, output on track 2. I then measured the delay of those two tracks by zooming in and comparing the two tracks visually: turns out to be 25ms (@88.2 kHz).

But: by entering those 25ms latency into the I/O options, the phasing and comb filter effects only get worse! By entering a high value of 500ms, I could confirm, that the I/O setup option was actually applying a correction - the delayed track 2 sounded like an echo to track 1.

So, to me, it seems, that PT 2018 does try to automatically correct the latency of my RME UFX II (maybe, it is reported back to PT by RME's drivers), but does not fully succeed - otherwise, it would not sound "strange", when playing back both tracks simultaneously.

So, I actually have two issues:
1. Phasing issues, when using the outboard gear directly inside PT
2. a 25ms delay, when printing certain tracks inside PT (for example using the summing amplifier for certain tracks) and bouncing those printed tracks together with the remaining "normal" tracks (who have NO delay) to a stereo mix.


Maybe, I am really mixing up things here, and I apologize in advance if I did. Plus: there is so much contradictory info out there about ADC and outboard gear like "it is only working, when you use it as an insert", "it will work both as an insert and on a send", "it will not work on a send or used on an output"...

I just hope, that with your help, I can figure out and solve the problem.
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  #2  
Old 09-02-2018, 10:41 AM
albee1952 albee1952 is offline
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Default Re: Latency issue (analog outboard gear on RME Fireface UFX II / PT 2018.7)

Some things to consider:
1-Yes, PT does not compensate automatically with any 3rd party interface, so you need to figure out the actual latency and enter that value in the Delay Compensation tab of the IO setup.

2-Remember that delay compensation can only move things later in time(to match the track with the highest total latency) so you might not be able to track with a hardware insert(that's the nature of "the beast"

3-What hardware are you trying to use? I ask because many folks go down this road for hardware that simply doesn't warrant the hassle. Remember that "budget" hardware can be beaten by any number of plugins without the hassle

4-Total latency will also be affected by the buffer setting, so a compensation amount calculated for a 128 buffer may not work correctly if the buffer is at 1024.

Lots to think about
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  #3  
Old 09-02-2018, 11:49 AM
dvdr dvdr is offline
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Default Re: Latency issue (analog outboard gear on RME Fireface UFX II / PT 2018.7)

Quote:
Originally Posted by albee1952 View Post
Some things to consider:
...
Lots to think about
Dave

Thanks - I thought I thought about it a lot. But I hit a wall in understanding

- currently, I am only dealing with the latency issue in mixing. Not dealt with latency in tracking at all... so let's stick to mixing (88.2 kHz, 24bit, 1024 buffer).

- did I measure the outboard latency properly? I described my way above.

- my understanding so far was, that PT automatically delays each track individually to match each one up to the track with the biggest latency - whether that track contains processing from "in the box" or using properly set up outboard gear.

- I/O settings provide latency setup for outboard gear, so if I enter the "roundtrip" latency of my RME there, I was expecting PT to take this into account: but entering a value there seemed only to worsen the situation.

- as for printing stems using the summing mixer: why the delay there, if I entered the 25ms latency of my RME in I/O settings? Shouldn't PT take care of that, or why else bother to have a settings page for I/O latency at all? And: in which situation will PT not be able to use this value?

Thanks for being understanding and patient with my questions!
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  #4  
Old 09-02-2018, 02:36 PM
albee1952 albee1952 is offline
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Default Re: Latency issue (analog outboard gear on RME Fireface UFX II / PT 2018.7)

Quote:
Originally Posted by dvdr View Post
Dave



- as for printing stems using the summing mixer: why the delay there, if I entered the 25ms latency of my RME in I/O settings? Shouldn't PT take care of that, or why else bother to have a settings page for I/O latency at all? And: in which situation will PT not be able to use this value?

Thanks for being understanding and patient with my questions!
I wish I could be more precise with my advice, but I don't have the same hardware so I am shooting from the hip a bit(and hopefully someone else can jump in with better help).

I think you have 2 things that are actually separate issues; the hardware insert latency, and the summing mixer latency. The inserts need to use a matched set of IO(such as output 6 with input 6) and I think you have that correct. where are you entering your 25ms setting? On the tracks at the bottom, or in the Delay Compensation tab of the IO setup(which is where this belongs)?

How you feed the summing mixer is another matter. If you have master faders(with plugins) in play and are sending "stems" out to the summing box, know that master track latency is not compensated for.

I suggest a more surgical approach. Skip the hardware inserts for now and concentrate on getting the summing box working right. Best practice is likely to be; send every track out-thru the summing box-and back onto a stereo audio "mix" track. You need to monitor ONLY the track that the summing box is feeding.(anything that doesn't go out>thru summing>back in, is going to be out of time with everything that DOES). Once you get this part ironed out, then look into the insert compensation(one key part of troubleshooting is; remove as many variables as you can)

Again, what hardware exactly? It may help to get better advice if we know what actual hardware you have
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  #5  
Old 09-02-2018, 03:38 PM
dvdr dvdr is offline
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Default Re: Latency issue (analog outboard gear on RME Fireface UFX II / PT 2018.7)

albee1952, Thanks for jumping in.

My hardware, as describe above:
PT 2018.7
RME Fireface UFX II (via USB)
RME Fireface 800 (connected via ADAT to the UFX II as just a "channel expansion", adding 8 more analog Inputs and Outputs).
Analog outboard gear is connected directly to the UFX II - currently an Avalon AD 2044 compressor, a TL Audio Ebony A4 summing amplifier and a tube EQ on loan from a friend. (Let's please not discuss analog gear quality, right now, I am only trying to figure out the proper delay compensation setup.)

To answer your first set of questions:

- matched IO: of course!
- entering hardware delay compensation: in IO setup, of course, as described above
- But, as I said: entering a delay value in IO setup (in my case 25ms), only makes things worse. It seems, as if PT knows about the hardware delay of my RME Fireface (maybe through the driver??), but not perfectly compensates it and by entering 25ms compensation in IO settings, only adds unnecessary ADDITIONAL delay compensation

So, this is what I do to hear those phasing issues:
load ONE stereo file into a new session. Create two stereo tracks and one master track, put the stereo file into BOTH tracks.
Play the session with BOTH tracks active:
a. without plugin in track 2: clean result
b. with any of my hardware as a plugin in track 2: phasing issues.

As to your second set of questions
I am feeding the summing mixer via this workflow:

1. I have 16 analog outputs available from my Firefaces, 14 are directly wired to the summing amplifier, 2 go into my monitors.
2. I decide, which of the tracks should be "stemmed" - for example brass, chorus voices, strings etc.
3. so, I start with the brass. For each brass track (mono or stereo), I chose a separate channel of my Firefaces as the track's output and feed those outputs directly into the summing amp's individual channels. I am not using subgroups, I am not using aux-tracks or master tracks for this - each individual track directly gets assigned its own, dedicated summing amp channel via an individual analog output of my Firefaces.
4. The summing amp's stereo output is recorded / printed to a new stereo track in my session.
5. After I printed the brass, I repeat the same procedure with chorus voices, strings etc.
6. Monitoring is no issue at the moment of creating the stems, since the tracks already have their proper processing, volume, automation. So "stemming" is merely some processing work done without the need for monitoring.
7. I end up with a certain amount of printed stereo tracks / stems plus some "unstemmed" tracks, that remain "as is" in the session. I then proceed to finalizing the mix by muting all unnecessary tracks and just continuing my work with the stems and the remaining "unstemmed" tracks.

But: there is a 25ms delay between the remaining, "unstemmed" tracks and my created stems, despite me having entered the 25ms delay in IO settings. So there is no way to continue mixing with bunch of tracks, that clearly are not "in sync".

So, either my understanding of the summing mixer process is completely off the rail, or, again, PT does something strange.

Thanks again for helping me in that matter.

Last edited by dvdr; 09-02-2018 at 03:56 PM.
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  #6  
Old 09-03-2018, 10:40 AM
albee1952 albee1952 is offline
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Default Re: Latency issue (analog outboard gear on RME Fireface UFX II / PT 2018.7)

Sadly, I am going to bow out on this. I think the way you want to do things is maybe never going to work the way you wish it would(but I will be happy to see someone prove me wrong)
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The better I drink...the more I mix.....

BTW, my name is Dave, but most people call me.........................Dave
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