[geoff]

On 23/01/2021 9:24 pm, Paul Dorman wrote:
In the electrical test and adjustment procedure, this organ service
manual asks for an "Audio VTVM", to measure Tibia or Bourdon
channel levels, to meter readings of +5dB (1.4 VAC) for example, either
at one of the speaker voice coils, or at the crossover.

Obviously, VTVM stands for vacuum tube volt meter, but can I just use my
regular Volt-Ohm-Meter in AC voltage measurement setting, to
make these measurements?




Thatwas written in the days when the only other option to a VTVM where
moving coil voltmeters, which have a relatively low input
impedance/resistance rating in (k)ohms/volt.

Just use a DMM and Bob's your uncle.

My meter is NOT a True-RMS meter, so I know if the signal is too far
off
from an ideal sinusoid, the RMS reading will be off, but I am hoping it
will be close enough.

And I assume +5dB means +5 Decibels Above the Noise Floor, but I have
never used an audio meter that measured in dB. I would guess that with
such a meter, you would normalize 0 dB to the noise floor, with no
signal?

A bit of a loose use of dB there, but I would assume it means +5 dBV,
near as dammit 1.8v (unless they actually state something about 'above
noise floor'.

geoff

geoff