Help calibrate levels btwn digital (Lynx) and mixer (Studer)

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Flight Feathers
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Help calibrate levels btwn digital (Lynx) and mixer (Studer)

Post by Flight Feathers » Fri Apr 06, 2012 2:29 pm

Hello everyone

i'm wondering if I could get some basic instructions on how to calibrate levels between the analog and digital worlds. I'm using Logic, going out of a Lynx Aurora 16, into a Studer 269.

It is my understanding that +4 dBu out from the Lynx should read 1.223 ac volts. So I set up a test tone in Logic at 1k outputting at level "0". I plugged in a patch cable at the output on the patchbay, put my multimeter across the ring and tip, set it to AC voltage, and got a reading of 1.04. I know there are different ways to read ac voltage - RMS, peak, something else. Is it possible my multimeter is not displaying the right value?

I'm not clear on what to do next. Any help would be really appreciated.

thanks
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Post by farview » Fri Apr 06, 2012 4:20 pm

0dbVU is 1.223 volts, but you were measuring 0dbFS. It's two different things.


You need to go the other way and send a 0dbVU signal out of your mixer and into the Lynx. Then look on your input meter in your DAW and see what it reads. It will probably read somewhere between -15 and -18dbfs in your DAW. That will give you the DAW meter reading for line level.

I'm not familiar with the Lynx card, but I'm assuming you can't calibrate it.


In a nutshell, 0dbVU in the analog world is line level. VU meters are slow and just give you an average signal level reading. 0dbVU is the target for a good signal. The transients are not measured by the meter and will exceed the indicated level by 18 or 20db in some cases.

Digital meters are very fast and read the transient peaks in the signal. 0dbFS is the highest level that can be recorded in digital, you can't go above 0dbfs. Line level will correlate to -18db(or something around there) in the DAW because the dbFS scale in the DAW is referenced to full scale. This means that there are only negative numbers in the DAW, so you need to allow headroom to catch the transients.

You will never get the meter on your mixer to read the same as the meter in your DAW. They are reading two different things, using two different db scales with two different reference points.

When setting recording levels, the best way is to output 0dbVU from the mixer and make sure that the input meter in the computer isn't clipping. That's all you have to do.

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Post by brew » Sun Apr 08, 2012 9:22 pm

It's 1.228 volts. You guys are rounding the wrong number in the wrong place. Some people shorthand it as 1.23, but when it is rounded to the thousandths it is 1.228 Vrms. Since most voltmeters will go to this many places might as well do it right. Across +/- for a balanced output of the Lynx, measuring AC. Most voltmeters only measure RMS so it's not an issue. Use this too.

The mistake you've made is you didn't pick a digital reference level for +4 dBu. You have test tone at 0, what does that mean? It's important to be clear. 0 dBFS? That would equal the maximum output, not +4 dBu. Also, you need to account for pan law, so preferably don't use stereo to do this. For the un-cal'd Lynx you'll find +4 dBu with -16 dBFS tone, since 4+16=20, the max output.

Gather all your max IO levels for the gear. The Aurora 16 has two different depending on the version, the uncal'd is +20 dBu. The Studer says it is +23 dBu on the line inputs.

Personally, your analog mixer will sound better if you don't use modern digital output cal levels of >+20 dBu. If you have just 3-4 full scale tracks you're going to be clipping your Studer. You would probably get better sounding results by aiming for more analog-tape-like levels of +14 dBu max. You could also change the VU line up level to be 0 VU = 0 dBu, so that you are encouraged to record lower. See this for how to use a VU. Read BK's level articles for why you might stay away from hot outputs with analog consoles. You might find the Studer actually sounds better if you switch the Aurora to its -10 dBV setting. This way you aren't overloading the desk straight away, which is a common mistake these days.

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Post by Flight Feathers » Mon Apr 09, 2012 9:46 am

Thanks for the detailed responses, it is really helpful.

I guess a lot of my confusion is with calibrating the Studer itself. The board has a built in 1kHz test tone oscillator, so I sent that to the 2 master output channels. I adjusted the master faders so they were reading 0VU on the board's VU meters. On the Lynx, 0VU off the board was reading -17dbFS for each channel. It is my understanding that this level is subjective, it could be anywhere between -16 and -20dbFS. I guess having the Variable Trim Lynx until would let you dial this in. My problem is, the master faders on the Studer are not aligned at 0VU, one is at about -30 on the scale printed next to the faders, the other one is at -40.

So, my question is what do I adjust to get the Studer master faders to be parallel at 0VU? I pulled out the channel strips and there are several adjustable trimpots on there. I'm reading the manual, but it's confusing.

Also, it seems like the board is outputting really hot, the master faders are pulled way down to get 0VU.

And do the printed numbers next to the faders actually reference any scale, or are the numbers just arbitrary?

thanks again
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Post by farview » Mon Apr 09, 2012 11:13 am

I think your main problem is you don't have any standard to calibrate anything to. The signal generator in the studer isn't putting out a line level signal. Since you don't know what level the signal is, you can't use it to calibrate anything.

Now that you know a 0dbVU signal is a -17dbFS signal, send a -17dbfs signal out of the computer into a line input on the studer. If there is a trim adjustment on the studer, adjust the trim so the meter reads 0dbVU on that channel.

Theoretically, if you put that channel fader at 0 and send it to the master fader set to 0, you should be getting 0dbVU on the output meter on the board and -17dbfs on the input meter of the DAW..

I am not familiar with the Lynx, so I don't know if you can change the calibration on it. If you can't, there really isn't anything for you to do other than calibrate the input of the mixer to accept a line level signal. Of course that assumes you will be using the mixer to mix stems from the DAW. If not, there is really nothing for you to calibrate.

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Post by brew » Mon Apr 09, 2012 2:57 pm

I wouldn't use a console osc to line up equipment. As farview says, who knows what it is. A console osc is good for troubleshooting and ballparking, but not for anything that requires <1 dB adjustment.

However, the Studer manual is very good and has routines for checking line up.

Don't worry about your master faders so much because remember you don't know what your OSC is cal'd to--it can't be trusted unless you cal it yourself with your voltmeter. Also, you don't know what your VU's are cal'd to so you can't trust those either.

Printed number 0 should represent unity through the fader. The other numbers are relative from there. Normally you leave everything hard panned and 0, unity, or detent when calibrating so you have 1-to-1 through the console. The Studer however has a 10 dB gain after the fader so that could affect your levels, just have to read the manual to find out.

Looks like a cool console!

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