DC meter as VU/GR meter?

[mitsos]

I know this has been covered before many times, but all the threads I found do not seem to go anywhere..

I have a few DC meters (I think they are 1mA maybe, but need to check...) that I'd like to use as VUs. First thing is a DAOC compressor I'm finishing up.  Is this as simple as rectifying/buffering the signal going to the meter? 

thanks!

 

[JohnRoberts]

Yes, rectify to DC and scale for full scale. If meter is 1 mA you don't need a buffer, but meter will read like typical VU meters, so only 3dB between 70% and 100%, etc.

Typical mechanical VU meters are fed from average of audio because peak would make the scale look even worse. If you added peak detection and scaled 100% for +20 dBu, 0VU would = 5% of full scale.

Enjoy... 

JR

 

[mitsos]

cool, hope it works off the bat.  For rectification, would 4 selenium/germanium/etc diodes do the trick or should I do a active rectification like in Keith's LED bargraph (attached)

As for scaling it, is that just with the series R, in which case I could use a 10K trimpot?

cheers! thanks for the answers!

 

[gyraf]

For VU, schottky diodes work fine.

Usually (the ones I've seen recently) VU-meters are 100-200uA movements

Jakob E.

 

[PRR]

VU meter movement is 200uA.

A 1mA meter would scale-out as something like 800 Ohms, which is a very heavy load on a classic 600r line. You'd want to buffer.

With a big enuff buffer ANY meter will work. Strap a couple of power-amps together, I could use the 10 Amp battery-charging meter on my tractor. Little 1mA and 10mA meters can be driven with nearly any 29-cent opamp.