vu meter mod

[polyal]

the FSD of a vu meter is usually no sound to
overloading (-24 to +9 )approx

i need to modify the characteristics so FSD
reads -6 to +3 ( approx ) via a specific or
modified meter driver

can anyone help with suggestions or pointers etc
(this is a DIY proj)

thank you
al saunders
stoke on trent UK

[Cal Weldon]

Moved to everything else.

[acid_k2]

- zener diode in series to the signal path (cut lower signal)
- op-amp with about 3dB gain, or more..(amplifies remaining upper signal)
- re-drawn of the dB scale

[jackinnj]

One of the linear tech guys did an article in EDN for an 80dB range VU Meter -- with the proper attack and decay times:

[acid_k2]

@jackinnj
polyal ask for less vu-meter range... from 30dB range to about 10dB range.

[Iain McNeill]

you need gain and an offset - not possible in a passive solution. Something like Jackinnj's posting is about the minimum for accurate VU ballistics. You can also check out Analog Devices - they have all sorts of IC's for this with very good performance.
http://www.analog.com/static/importe...ection_III.pdf

[jackinnj]

You can use a window comparator to set the range -- throw away the data below and above the window and just measure what's contained in between. You can easily do this with an dual comparator and an opamp which has "Shutdown" although most of these are SOIC or MSOP. If you don't want to screw around with surface mount just use a JFET as a switch.

The circuit I provided will get you the right ballistics -- and there are others on the web as well.

Remember that 0 dBm is 1 milliWatt into 600 ohms -- approximately .774 volts --