C|24, 192, PT meters not making sense

[Parks]

I work on a couple of these systems and they all seem to have the same problem: using an outboard pre (Avalon) or just keyboards etc in general, will go go into the Pres on the C24 where they seem to ignite the "clip" lights fair early, the 192's will still be fairly modest and the meters on the channels in PT often appearing even lower than the 192...what's the remedy here? I've messed with the -10/+4 settings in Pro Tools hardware setup and that's certainly not helping...anyone?

[Darryl Ramm]

Originally Posted by Parks

I work on a couple of these systems and they all seem to have the same problem: using an outboard pre (Avalon) or just keyboards etc in general, will go go into the Pres on the C24 where they seem to ignite the "clip" lights fair early, the 192's will still be fairly modest and the meters on the channels in PT often appearing even lower than the 192...what's the remedy here? I've messed with the -10/+4 settings in Pro Tools hardware setup and that's certainly not helping...anyone?

Why are you using the preamps on the C|24 at all if you have outboard preamps or line level signals? If you feed line level signals into the Mic preamps of course they will clip. Do you mean you are using the line inputs? Whole different connector... and do you really need to do that? Why? For a mix? monitoring. The C|24 is a OK control surface, with less than great preamps and less than great monitoring section IMNSHO... and better to treat it like that if you can and focus on the control surface.

First test is plug your line level inputs direct into the 192. If needed get a patch panel or break-out cable. Does that look right?

[Parks]

Yes, when I say Pre I meant using the amp circuit in general, I'm not plugging line level signals into the microphone preamp...but line level signals do (not infrequently) need a boost.

No one else has ever had this problem? Is there a calibration that can/needs to be done? I can't find anything in the C24's utility menus

[Darryl Ramm]

OK but the second part of that is why are you going into the C|24 at all with those signals?

And even if you need to go into the C|24 for monitoring reasons what happens if you go direct into the HD interface?

You have a pretty good digital interface there, with both pro and consumer line level inputs and with 24 bit dynamic range and clean electronics, you really should not need to "boost" line levels.

You do have the C|24 connected to the +4dBu inputs not the -10dBV inputs on the 192 right? If you are mixing up consumer and pro level components just connect each of them directly to the 192 to the appropriate connector.

[Drew Mazurek]

Originally Posted by Parks

Yes, when I say Pre I meant using the amp circuit in general, I'm not plugging line level signals into the microphone preamp...but line level signals do (not infrequently) need a boost.

No one else has ever had this problem? Is there a calibration that can/needs to be done? I can't find anything in the C24's utility menus

Are you familiar with how the analog world of voltage (dBu) interacts with the digital word of dBFS? Pro Tools interfaces are calibrated so that -18bBFS = +4dBu, which is also = 0dBVU. So a good "heathy" signal in the analog world, if you don't understand this, "looks" low in dBFS. This is VERY common and causes MANY people (dare I say most nowadays) to run their analog gear too hot thinking they need to record as hot as possible.

[Parks]

Darryl, I appreciate your input, but if you don't understand why you might need to boost line level signals from time to time I'm not sure theres much here to discuss.

Of COURSE I'd love to bypass all of the analog portion of the C24, but these are not MY studios, which I thought was implied by "I work on these systems"...so telling someone to go out and drop $10k in the analogue front end for a system that I[I] prefer isn't very helpful...

I understand gain staging in the digital world quite well...I've been working on DAW's since the late 90's and have a couple gold records to show for it...I've also helped several major producers with setting up their studios...

BUT

What I have NOT encountered, is this huge of difference in metering, except on C24 systems...TYPICALLY...a properly gain staged Microphone-->Preamp-->Compressor signal path going into a 192, 96i/o Apogee, whatever system will translate at least fairly reasonably (I'd say within at most 3dB)...even the old Control 24 systems made sense for the most part as far as metering goes, but these C24's either Clip (or at least warn you of a clip) WAY early, or output really low or SOMETHING that i was hoping for some clarification on.

[Darryl Ramm]

I suspect you might benefit from sitting down and systematically debugging things.

The clip indicator in the C|24 is purely analog, if its clipping your input signal is too hot, or the C|24 is faulty or a mic input is accidentally being used with a line level input. There is no user calibration/relevant setup stuff to mess with. So just work out what is going on. Run your own gain stage measurements. Stick a test signal (at a minimum the test rig is right in front of you... use a signal gen plugin sine wave out of your 192 IO, with level checked with a good multimeter) into that input and/or or a scope on the signal and confirm exactly what is happening. And confirm the C|24 output is going into the +4dBu inputs on the 192 IO (and ideally the 192 IO is calibrated).

Drew gave you the comparison numbers, which hopefully you already knew... so instead of talking about "looks low" etc., what do you measure on these systems? Actual analog input dBu to the input of the C|24? At it's output/intot eh 192 IO and what does Pro Tools show in dbFS?

I'm not sure what you mean by the meters 'appearing even lower on the C|24'. What meters are you looking at/comparing to? The channel meters on the C|24 are purely digital/fed from Pro Tools and have no way of knowing that actual analog level of any signal in the C|24. Do they agree with what Pro Tools is showing? That is all you can every want/expect them to do. What meter mode etc. are you in in Pro Tools?

I understand you can't always mess with somebody's setup, but if things are not working properly/as expected then you kinda do need to investigate it, at least futz around with it to do some tests.

[spwwuk]

Yes, I've had the same experience with the C|24 inputs clipping way before the meters on the HD I/O.

[Darryl Ramm]

Originally Posted by spwwuk

Yes, I've had the same experience with the C|24 inputs clipping way before the meters on the HD I/O.

You talking preamp inputs? If so you are driving a preamp and then connecting that preamp output to a line-level input on an interface. i am not sure why you expect that a over-signal "clipping" indication in the preamp should correspond closely to a 0dB display on the HD IO meter.

To be fair, of course you may not be assuming/expecting any behavior and just reporting what happens. I just want folks to think through the signal chain here and what different levels are actually involved and what different analog or digital meters mean.

[Darryl Ramm]

BTW also be aware of the padding added to C|24. And it may be useful to differentiate between older and newer (-20dB padded) C|24.

http://duc.avid.com/showthread.php?t=303896