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how to calibrate my AD converter
Old 23rd May 2006
  #1
Gear Nut
 

how to calibrate my AD converter

I think I'm ready to tackle this. My Lavry Blue AD is factory calibrated at -20, but I want to calibrate to something like -16. I have a Great River MP2NV and PTLe (Digi001), which can produce a 1Khz tone. How would I go about calibrating the AD converter with this setup. I know how trim the Lavry, I just want a step by step procedure on how to go from the tone generator to the AD converter. Will I need an outboard tone generator or is the PTLe good enough?
Old 23rd May 2006
  #2
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Riad's Avatar
 

You can't use the tone generator that's built into protools...

I used my CT100 cable tester that has a 1khz tone generator

http://www.americanmusical.com/item-...BEH-CT100.html
Old 23rd May 2006
  #3
Gear Nut
 

Thanks. But I really don't know how to do this step by step. Can you help?
Old 23rd May 2006
  #4
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Riad's Avatar
 

Well I don't know how it works on the Lavery, I have the Apogee AD16/DA16-x converters and they have a calibration mode.

I use the tone generator and patch it into the first input of the Apogee and then either raise or lower the value until you hit -16.
Old 23rd May 2006
  #5
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doug_hti's Avatar
 

Haven't used Lavry, but I'm guessing there is an input pot to adjust for calibration.

You need a true RMS multimeter to measure voltage.
A bit of the problem is that your LE system can't be calibrated on it's converter, so the output will remain fixed (prob -18ish).

Once you have the multimeter reading ac voltage hook a cable out of your Protools interface with nothing else between, put some bare wires, or whatever it takes to get a signal to the multimeter.

In pro tools set up signal generator out of one of the outputs, use a 1k tone and adjust the ouput level of it (signal generator) until your multimeter reads 1.43 volts. Once you get it as close as possible (to the 10th of a decibel from "signal generator") then don't touch a thing.

Open up two mono aux tracks, solo safe them, bus the outputs to an unused "bus" so "bus 25 or something). Adjust the inputs to be coming from the Lavry A/D....(so digital 1 and 2 or whatever your I/O setup says). Just make sure the output is NOT NOT NOT 1/2 or your main output or you will have a feedback loop.

In ProTools (maybe under setup), put the software into "calibration mode". This will continuously reset the peak input on the meters (where it reads the numbers on the channel strip) (press option/click on numbers to cycle through if it doesn't automatically go to continuous peak input on numbers (in mix window)

now feed your output to the A/D input and adjust the A/D pot until your protools peak input meter reads -16.

PM me if you need further help. The only thing, I'm not sure if LE has calibration mode, but I'm pretty sure it does.

Just remember your outputs (if using stock converts) will not be at -16 of full scale.
And you will see what they are pretty much calibrated at while finding the right output level on the signal gen
Old 23rd May 2006
  #6
Gear Maniac
 
jazztone's Avatar
 

Please exscuse my ingnorance on the subject but are we talkin about calibrating the metering in said DAW to ensure it reads accurate to the level the AD is seeing? If not what is the calibration and can it be done to a RME Fireface?


Quote:
Originally Posted by doug_hti
Haven't used Lavry, but I'm guessing there is an input pot to adjust for calibration.

You need a true RMS multimeter to measure voltage.
A bit of the problem is that your LE system can't be calibrated on it's converter, so the output will remain fixed (prob -18ish).

Once you have the multimeter reading ac voltage hook a cable out of your Protools interface with nothing else between, put some bare wires, or whatever it takes to get a signal to the multimeter.

In pro tools set up signal generator out of one of the outputs, use a 1k tone and adjust the ouput level of it (signal generator) until your multimeter reads 1.43 volts. Once you get it as close as possible (to the 10th of a decibel from "signal generator") then don't touch a thing.

Open up two mono aux tracks, solo safe them, bus the outputs to an unused "bus" so "bus 25 or something). Adjust the inputs to be coming from the Lavry A/D....(so digital 1 and 2 or whatever your I/O setup says). Just make sure the output is NOT NOT NOT 1/2 or your main output or you will have a feedback loop.

In ProTools (maybe under setup), put the software into "calibration mode". This will continuously reset the peak input on the meters (where it reads the numbers on the channel strip) (press option/click on numbers to cycle through if it doesn't automatically go to continuous peak input on numbers (in mix window)

now feed your output to the A/D input and adjust the A/D pot until your protools peak input meter reads -16.

PM me if you need further help. The only thing, I'm not sure if LE has calibration mode, but I'm pretty sure it does.

Just remember your outputs (if using stock converts) will not be at -16 of full scale.
And you will see what they are pretty much calibrated at while finding the right output level on the signal gen
Old 23rd May 2006
  #7
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doug_hti's Avatar
 

well most metering in DAWs are dbfs, so is "0" is at the very TOP of the meter? then there doesn't need to be a reference as the "0" is the top of the top.
However, in pro tools under preferences there is a 0dbvu reference level in which, I really don't know what that effects.....

if your RME fireface is a analog converter, then it may or may not be able to be calibrated. What do you need it calibrated to?
Old 23rd May 2006
  #8
Gear Maniac
 
jazztone's Avatar
 

Quote:
Originally Posted by doug_hti
well most metering in DAWs are dbfs, so is "0" is at the very TOP of the meter? then there doesn't need to be a reference as the "0" is the top of the top.
However, in pro tools under preferences there is a 0dbvu reference level in which, I really don't know what that effects.....

if your RME fireface is a analog converter, then it may or may not be able to be calibrated. What do you need it calibrated to?


I use the Fireface 800 AD/DA with Logic 7.1.1 I have always noticed a signal in the RME Mixer about 8 DB hotter than the levels showing in Logic. This includes the waveform drawn for visual refernce. I always assumed this was just another problem with Logics metering( no intersample readings and inaccurate). If i could calibrate both mixers Logics and the Fireface so the meters read the same that would be fantastic.
Old 24th May 2006
  #9
Mastering
 

Quote:
Originally Posted by Riad
You can't use the tone generator that's built into protools...

I used my CT100 cable tester that has a 1khz tone generator

http://www.americanmusical.com/item-...BEH-CT100.html

I just wrote a 4-part series on this very subject and more! Articles in Resolution Magazine...


BK
Old 24th May 2006
  #10
Gear Nut
 

Riad:

I checked the CT100, and surely it can send a 1Khz test tone at +4dBu, although it says that it is not intended as a voltage standard and the battery voltage will affect the test tone output level (??). Will this affect the calibration? Does it have to be very very precise?
Old 24th May 2006
  #11
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doug_hti's Avatar
 

Quote:
Originally Posted by rems
Riad:

I checked the CT100, and surely it can send a 1Khz test tone at +4dBu, although it says that it is not intended as a voltage standard and the battery voltage will affect the test tone output level (??). Will this affect the calibration? Does it have to be very very precise?
why do you need the ct100
Old 24th May 2006
  #12
Gear Nut
 

I don't know much about calibrating, but I guess what Riad does is that he would send a 1Khz tone at +4dBu from the CT100 via XLR to the AD converter's inputs (AES/EBU). Using the Lavry's trim pots on front, I would proceed to calibrate the unit so it reads -18dbU (or whatever I want) with that signal.
Old 29th May 2006
  #13
Gear Nut
 

I want to let everyone know how well it went with Riad's recommendation. I used the CT100's mic out>Lavry Blue AD AES/EBU in>PTLe 6.4. Switched the CT100 to send a 1 Khz signal at +4Dbu and PT's meters registered a -19.2 source. I knew that the Lavry was factory calibrated at -20, so I knew that I was doing good. I placed a jeweler's scredriver to trim tha Lavry's trim pots and moved them until I got -16 on the Lavry's meters. It also registered -16 on PT's meter. So, mission accomplished!
Old 29th May 2006
  #14
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Riad's Avatar
 

That's awesome dude, glad I could help. Sorry I didn't respond to the earlier posts with questions, I've been up to my eyeballs as they say.

Can't wait to read Bob's articles on calibration!
Old 6th October 2006
  #15
Lives for gear
 
Switchcraft's Avatar
 

So will calibrating the lavry output to 1.5V via a 1K tone at 0dB give me a 0dB level ouput?
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