Calibration/Reference levels

[Mark Wheaton]

I have a ProTools system connected to an analog professional console: Soundtracs Solitaire. I have been using the standard -18 ref level. Everything is +4 on this system.
My problem has been that using that standard, the meters on my board are useless, (they totally pin when you have what seems to be proper levels in digital land.) and I am very close to the headroom limits of the board, so I am taxing all the electronics and risking clipping my inputs, outputs etc.

And, it is difficult to route a signal through the mix bus and know what the levels are.

That said, I decided it might be good to change the ref level to -12 or -14. In fact, trying two channels seems to indicate better metering on the console. My question is:
Is there any implications as far as Pro Tools is concerned especially related to mixes I already have which may be too hot for the readjusted levels?
Anybody out there with experience calibrating between Pro Tools and pro analog consoles who have opinions, formulas, experience etc I would greatly appreciate your comments.
Thanks

[Mark Wheaton]

That part I understand, at -18 I do get 0vu on my console meters. But by using that reference level, when I play back files in Pro tools that are within a couple of DBs of digital ceiling, the meters on the console are then peaked out completely. Since I do mix at close to the digital ceiling I have no way to use the consoles meters to know what my levels are. My point is that by setting the ref level to -14 or -12, the output of Pro tools is turned down and so hot levels read better on the console meters. I am asking if there are any issues with lowering pro tools headroom like that, especially regarding previous mixes that were done using the -18 ref level?

[Park Seward]

You are talking about the calibration level. Since -18 gives you a lot of headroom, you will see the meters slamming if you get close to "digital zero", which is 18 dbu over "0" on your VU meter.

You can recalibrate the system and use -10 as your zero reference or even 0 if your bhoard has that ability. It's all relative, as long as you can set your operating level. Some professional meters have many different calibrations to allow you to set the reference level anywhere you want.

You are also comparing a VU meter on your board to peak meters on Pro Tools. The two don't read the same.

There is nothing wrong with headroom. In analog, we set the levels as high above the noise floor as possible and as low a distortion figure as possible. That means a compromise. Since digital has little distortion until we clip, to most people that means we should get as close to digital 0 as possible. I don't think that is necessary.

Pick an operating level and stick to it. The industry has picked -18 for all professional digital videotape recorders, for example.

[Steve MacMillan]

Mark,

Try recalibrating your system for -14 or -12. If you are still pegging your console at the input from ProTools. Turn down the ProTools mixer faders until you are not spanking your mixing board.

sm

[agus]

Sounds like you're comparing vu meters to digital level meters. What's on the analog console for metering?

The -18 out of PT should line up at 0vu on the console if all is calibrated.

[agus]

Sounds like you're comparing vu meters to digital level meters. What's on the analog console for metering?

The -18 out of PT should line up at 0vu on the console if all is calibrated.

[Don Geppert]

Mark

We have a TDM system integrated to an analog console and I have the reference levels in ProTools set for -13 (For some reason I can't get the 888's down to -12?). This certainly equates the levels on PT's much better to the VU's on the analog board. I know exactly what you're talking about. At a reference of -18, full scale PT's levels will certainly pin out your analog VU's. As mentioned in other suggestions above, try re-setting your I/O levels in PT's. If you need more help email me.

Best

[img]images/icons/cool.gif[/img]

[Mark Wheaton]

thanks Don for the info on your system. this is the first time I have found someone who completely understands the issue. And, I too when trying -12 found the 888's would not go down that far. i was thinking of compromising at -14.

And the idea of pulling back the faders is good, I in fact do this on my mix track under my current -18 setting so when I monitor the output of my mix track it matches levels I get when playing back the finished CD routed into line inputs on the board at unity (from a balanced out CD player)

[mstucker]

Mark,
We have the same issues here, and have gone for the -14dB FS =+4dBu approach. We move our pro tools system between two rooms and tow different vintage consoles (API and Sphere) and this level works great for the API and OK for the Sphere. My philosophy is to ignore the VU meters, they are an analog device and don't show what you need to see while working in digital. The only real question is how do the levels work with the headrooom in your console. That, unfortunately is different for every console. You just have to spend some time finding the level that works for you. As to Park's post that getting to "0" in digital is not neccessary, the farther away from "0" your peaks are, the fewer bits you are recording with, thus the lower the signal to error ratio..... [img]images/icons/grin.gif[/img]