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Gain staging / Calibrating Recording Chain
Old 26th December 2019
  #1
Gear Head
 

Gain staging / Calibrating Recording Chain

Hello all,

I recently purchased a Behringer CT100 test tone / cable tester so that I could calibrate my analog and digital recording chain.

I'm finding some unexpected results.

On the Behringer CT100, I set it to generate a +4dBu test tone at 1000Hz, and use a multimeter to test the output voltage.

With the multi-meter set to AC measurement, I receive a reading of 0.5V. I believe this to be half of the AC waveform, and must x2 which suggests a reading of 1V.

I was expecting to have a reading of 0.6v which would be closer to 1.23V for +4dBu.

Is this a problem with the Behringer CT100, and should I be using a different brand?

I've been listening to the following youtube advice to calibrate my system.

https://www.youtube.com/watch?v=VGzE...1&index=3&t=0s
Old 27th December 2019
  #2
Lives for gear
 
Radardoug's Avatar
 

OK, so do you know if your multimeter will read a.c. at 1kHz or above? Most of them dont. You really need an audio millivoltmeter or similar. Even an old vtvm is probably better than most digital multimeters. The heath company made them as kits in the old days.
Where did you get the idea that the meter reading needed to be doubled? Wrong! A good meter should be easy to read and calibrated.
And that Youtube video tells you nothing!
Old 27th December 2019
  #3
Gear Head
 

Quote:
Originally Posted by Radardoug View Post
OK, so do you know if your multimeter will read a.c. at 1kHz or above? Most of them dont. You really need an audio millivoltmeter or similar. Even an old vtvm is probably better than most digital multimeters. The heath company made them as kits in the old days.
Where did you get the idea that the meter reading needed to be doubled? Wrong! A good meter should be easy to read and calibrated.
And that Youtube video tells you nothing!
I don't think my multimeter measures in millivolt. Is this the one you're suggesting?

https://www.ebay.com/itm/Heathkit-Mo...gAAOSw7aBeAeDt

I know that Fluke make great multimeters, would the following be suitable?

https://www.fluke.com/en-au/product/...ters/fluke-117

----

Regarding the doubling of the volt reading, this was suggested in some videos I watched. I'll delete that info from the memory bank.

---

In relation to the youtube clip, is there a good resource that you know of that explains how to calibrate everything end to end properly?

I'm using pro tools with a RME UFX II and Antelope Orion Gen 3 AD/DA converters, together with some outboard analog gear (DBX 165a compressor, Eventide H3000, chandler TG2 pre amp)

Thanks for your advice!
Old 27th December 2019
  #4
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ruffrecords's Avatar
Gain staging and calibration is not all that difficult. Can you start be describing your actual signal chain?

Cheers

Ian
Old 27th December 2019
  #5
Gear Head
 

Quote:
Originally Posted by ruffrecords View Post
Gain staging and calibration is not all that difficult. Can you start be describing your actual signal chain?

Cheers

Ian
Hi Ian,

My recording chain for tracking is:

Guitar/synth ----> RME mic pre (set to instr. level input) -----> H3000 ----> DBX 165a -----> RME Line input -----> Pro tools

I also want to send out to this chain from pro tools with inserts:

Pro tools -----> H3000 or DBX 165a ----> RME line input ----> Pro tools


----

On the analog devices I target 0dBu, and on the digital devices -18dBFS.

What do you suggest?

Thanks.
Old 27th December 2019
  #6
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Radardoug's Avatar
 

A VTVM like that would be OK, but there are lots of other meters too, many made by HP, and Japanese manufacturers. The Fluke you would need to check its data sheet, as to whether it will read audio frequencies accurately.
This one is ideal, and 2 channel.
https://www.ebay.com/itm/Leader-LMV-...AAAOSw0-5dt0d0
Old 27th December 2019
  #7
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ruffrecords's Avatar
Quote:
Originally Posted by jasonnevis View Post
Hi Ian,

My recording chain for tracking is:

Guitar/synth ----> RME mic pre (set to instr. level input) -----> H3000 ----> DBX 165a -----> RME Line input -----> Pro tools

I also want to send out to this chain from pro tools with inserts:

Pro tools -----> H3000 or DBX 165a ----> RME line input ----> Pro tools


----

On the analog devices I target 0dBu, and on the digital devices -18dBFS.

What do you suggest?

Thanks.
You have two RME| devices listed - they make lots of products - exactly which ones are you using. Also no mention of a converter from protools to feed the H3000.

Cheers

Ian
Old 27th December 2019
  #8
Gear Head
 

Quote:
Originally Posted by ruffrecords View Post
You have two RME| devices listed - they make lots of products - exactly which ones are you using. Also no mention of a converter from protools to feed the H3000.

Cheers

Ian
Sorry, I'm using the RME UFX II. I'm going into the RME preamps (channels 9 - 12), then out of it, via the hardware outputs of the same RME UFX II, to the DBX and h3000, then back into the same RME UFX II inputs to pro tools.

The converter from pro tools to the H3000 is the same RME UFX II interface.
Old 27th December 2019
  #9
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ruffrecords's Avatar
Quote:
Originally Posted by jasonnevis View Post
Sorry, I'm using the RME UFX II. I'm going into the RME preamps (channels 9 - 12), then out of it, via the hardware outputs of the same RME UFX II, to the DBX and h3000, then back into the same RME UFX II inputs to pro tools.

The converter from pro tools to the H3000 is the same RME UFX II interface.
OK, so gain staging is mainly a matter of watching and measuring the level at various points in the chain. This was easy in the old days when everything went into and out of a mixer because the mixer provided comprehensive monitoring and metering. With a bunch of separate units this is not always as easy. However, you are reasonably OK. The RME has comprehensive metering, the H3000 I suggest you set to work at +4dBu as suggested in the manual and the DBX165 has a meter which I suggest you also calibrate to +4dBu as described in its manual.

I had a quick scan of the RME manual so I suggest you set the AD inputs to Lo Gain which will give a maximum input level of +19dBu. If you set the gain on the gutar/synth input so it operates around -15dBFS you outputs will be around +4dBu. I suggest you set the H3000 for +4dBu operating and using its meters to check the level going through it. Lastly the dbx165 has abuilt in meter. If you calibrate this for _4dBu operation you should be all set. Just keep an eye on the meters.

For driving the H300 from protools I think you need to set the DA outputs for high gain which again will set -15dBFS to about +4dBu (seems strange you set inputs to low gain and outputs to high gain for a nominal _4dBu operating level but that is what the manual seems to say).

After that, just keep an eye on the meters and set the gain for the instrument at the rme input.

Cheers

ian
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