VU meter damping spreadsheet

[Fonotec]

Passive VU meter damping for level setting and conventional ballistics. From Dr. Christopher Hicks, of CEDAR Audio (http://www.chu.cam.ac.uk/fellows/160-Christopher-Hicks)

(See attached file, VU.xls, for use in Excel.)

"1) Connect the meter, via a single 3900 Ohm resistor, straight from the DAT output.

2) Play a 1kHz test tone and adjust its level (in the digital domain) until the meter reads 0VU. Calculate the difference D between this level and -10dBfs (in other words, if you've adjusted it to -25dBfs, then D is 15, if it is -19dBfs, D is 9).

3) Put D into the attached spreadsheet, and read off R1 and R2

4) Connect the circuit as follows.
* Pin2 of the XLR goes to one end of R1.
* The other end of R1 goes to one terminal of the meter
* the other terminal of the meter goes to pin 3 of the XLR
* R2 is connected to the two terminals of the meter, "bridging" it, so to speak.
5) Check that a tone at -10dBfs reads 0VU

0 VU = - 18 dBFS?

You need 8dB less attenuation than before, so look up the values of R1 and R2 for D-8 (ie 7dB and 1dB for the two examples I gave).

Have fun!

CH

PS You won't be able to get exactly the right resistor values. Don't worry too much; either just get the nearest you can, or get closer by adding together two smaller resistors in series.

PPS Note that R1 and R2 are the only resistors. You remove the existing resistor from the meter."