Calibration Issue - Trim screw does not change anything

[buddyrocker]

Hello,

Trying to calibrate my Digi192's (I have two which I'll call Digi192 #1 and Digi192 #2) according to the owners manual, and am having an issue that I'm hoping is simple. Here is what I've done:

1. Opened the Calibration session and set calibration level to -18 as per instructions
2. Ensured that software has +4 and trim A selected in Hardware settings
3. Saw signal on board for channels 1 - 8 on Digi192 #1 for the calibration plugin signal
4. Saw signal on the Digi192 #1 front meters displaying calibration plugin signal
5. Put session into "Calibration Mode" from Options
6. Saw that Output is at -20
7. Saw that Input is at -85
8. Adjusted the Input A trim - Nothing changed in session
9. Adjusted the Output A trim - Nothing changed in session
10. Adjusted Input/Output A on Digi192 #2 just in case, nothing changed.

So basically, changing the trim screws does nothing in the session. No matter how much I turn the screw, nothing changes in the calibration readings in the session.

What am I doing wrong?? Any advice is greatly appreciated.

Thanks
Bud

[joninva1]

You need a volt meter. Look up the manual for the interface. The instructions are in there. You calibrate the outs first. What is it, -18 @ 1000hz Sine = 1.228 V or 0 VU. So you need to run the signal generator in the calibration session. Use the "Calibration Mode" once you have your outs calibrated to trim your inputs to the outputs. You connect your outs to your ins and run Calibration Mode to adjust those to eachother. That would be when you actually mess with the adjustments for your inputs. At least this is how I have been lead to think.

[buddyrocker]

Thanks Joninva1,

I have the manual, but it only goes over the method where you create a session, not a volt meter.

Is there a resource that talks about how to do this?

Thanks
Bud

[joninva1]

Everyone on the DUC seems to be very quiet on helping with calibration issues. perhaps even they don't know how.

Here's the instructions step by step on how to calibrate an HD I/O or 192.
I invite anyone who thinks this is wrong to correct me as well by the way but I'm pretty sure this is 100% the way to do it. This scenario below would be to calibrate to -20dBfs-

I go off the knowledge that 0VU= 1.228V

Go to the preferences and make sure the calibration is set at -20 under operation - Bottom Right of window - (it may be at -18)

If you probe the output of a TRS cable at the tip and the casing (tip being red, casing being black) on a DC scale (like 20 VDC scale) you'll get the output in Volts of each channel on the volt meter. If your snake terminates to XLR, you'll need the hot and the ground just the same.

Based on the manual and my research with calibration, if you play the test tone at -20dBfs in the Calibration Session and you unmute the tracks so that the tone plays through the outputs, you should see 1.228V at the output of each channel (You're measuring each out with a volt meter - One at a time) if the unit is calibrated at 20db headroom. If you did not see 1.228V you would then turn the adjustment screw for the channel you are metering with your volt meter until the output is 1.228V for the channel - Repeat until all channels are set at that output voltage. Once they are all set, connect the ins on your interface to the outs (easy to do with XLR - Or you can use a Planet Waves Modular snake cable that goes from db25 to db25).

Once all your outs are good - go into calibration mode (in a dropdown menu in protools HD) and the screen will start flashing and going crazy. This is normal. Now you can match the outputs to your inputs. You'll see the Inputs on the right in the mix window flashing and you'll see a number on each one of the dB it is set at. Make sure the test tone is playing through the system by unmuting the outs Adjust your INPUT screws for each channel until they are at -20. You'll notice that the channels stop blinking once they are set at -20. Once all Inputs match and are set at -20 dbfs you are calibrated. You'll notice all Inputs no longer blink. Some people do this/check calibration at outs and ins before each session.

In my case, I was only able to get 1.228V at -14 dBfs headroom. I couldn't get the outs up to 1.228V when feeding them the -20 dbfs tone from the calibration session. Turned the screws and at a point the level no longer gets any higher. I have a trouble ticket in with Avid to see what the deal is. Hopefully someone at Avid knows how to calibrate their own gear and can help me since the DUC has been silent. My HD I/O came with a card stating it was calibrated at the factory to -18. In the manual it states it was calibrated to -20 at the factory. (which is it Avid?)

[joninva1]

There's Also this....

Calibration help please! How do I calibrate my Digidesign audio interface?

Interfaces: 192 I/O, 888|24, 888, 442 Steps: 1. On a mono track in Pro Tools, instantiate a Signal Generator plug-in and assign the output of the track to the first mono output. Make sure that the fader is set to unity. 2. Set the Signal Generator's frequency to 1 kHz and select Sine Wave. 3. Adjust the level of the Signal Generator to your desired reference level. This is typically -18dB for a 192 I/O or an 888. 4. Using an AC Voltmeter, measure across pins 2 & 3 of the output XLR (or across the tip and ring of a TRS plug). Adjust the output trim pot until the voltage reads 1.228V (for +4dBu) or .316V (for -10dBV) 5. Assign the output of the audio track to the next mono output. 6. Repeat Steps 4 and 5 for each successive output. 7. Connect the last output to the first input and create a mono auxiliary input. Assign the input to the first mono input and the output to the first mono output. Make sure that the fader on the auxiliary input is at unity. 8. Using the voltmeter, measure the voltage across the first output. Adjust the trim of the first input until the meter reads 1.228V (for +4dBu) or .316V (for -10dBV). 9. Connect the last output to the next input. Re-assign the input of the auxiliary input track accordingly. 10. Repeat Steps 8 & 9 for each input. 11. Congratulations! You're done! References and Equations 0dBu (or 0dBv) = .775V 0dBV = 1V 0dBm = 1mW into 600? .775V into 600? 1V into 1000? Any other combination of V and ? to generate 1mW. 0VU = +8dBu broadcast radio +4dBu professional line level audio -10dBV consumer/semi-professional level audio +4dBu = 1.228V -10dBV = .316V To figure out what the level is in dBu: dBu = 20 x log(Volts/.775) To solve for the voltage in dBu: Volts = .775 x 10 (dB/20) To use the same equations for dBV, replace the .775V reference with the 1V reference. (Note the question marks should be Omega for Ohms)

[joninva1]

A correction to the above - Make sure your volt meter is set to AC and reads True RMS.