[BC] Weston VU Meters -

[Milton R. Holladay Jr.]

A standard VI requires a source of 3900 ohms to have correct ballistics;
this means a 3600 ohm resistor in series with the meter across a resistive
600 ohm circuit; this will give a level of +4 dBm at 0VU.
 The meter bridged directly across a 600 ohm circuit will read 0dBm at 0VU,
but will have incorrect ballistics and introduce distortion due to the
rectifier.
VU range extenders are stepped T attenuators that maintain a 3900 ohm source
for the meter; some had the 3600 ohms built in, some required it
externally..........
M
----- Original Message ----- 
From: <schleutker at schleutker.net>
To: "Broadcast Radio Mailing List" <broadcast at radiolists.net>
Sent: Thursday, November 10, 2005 3:59 PM
Subject: Re: [BC] Weston VU Meters -


>Many of the older rack mounted meters had switches that inserted
>resistors. It appeared to me that "Volume Units" had different
>meanings depending on what fed it.
>
A 'standard' VU meter had defined meter ballistics that were only valid
under certain conditions.
I may be a bit hazy on this part, but I believe the meter required a 3900
ohm series resistor and had to bridge a loaded 600 ohm  (maybe it was 500
ohm) line.    Anybody with a better memory who could clear the haze?

Douglas E. Schleutker
Vista, CA
doug at schleutker.net