About VU meters, again...

[FotisGR]

Hello, friends.
I found on local market some VU meters for 35 Euros each. They look very beautifull and quality, too. They are Italian made by Mega . Is there a trick or method to check them before i buy, if they are real vu meters like sifam? They have +- input.

Cheers
fotis

 

[electronaut]

The rude test would be to simply connect some line-level audio to them. If they work, you're a happy DIYer!

-E.

 

[Mark Burnley]

Hi Fotis,

You could always build NewYork Daves test oscillator:

http://electronicdave.myhosting.net/miscimages/400cycle.gif

It puts out 400Hz at about +4dBm. You could build it in a small case with a jack socket, run off a small PP3 9V battery (should be enough to get it going) Then calibrate it a t home (measure the output on an AC mV meter) and take a jack-to-crocodile-clip lead with you. Take a 3k6 resistor along too. Connect the output to the meter via the 3k6 series resistor (a "true" VU meter usually needs an external 3k6 resistor...) and measure the reading. See if it coincides with your mV meter reading.

If the needle bounces about, or vibrates in one spot, then it is a basic DC movement with no rectifier. If it gives you the equivalent VU reading for your mV measurement, it looks like you're in luck!

If it is an unknown DC movement, it still may be useful. Check my "mystery meters" post here for measuring an unknown movement:

http://www.groupdiy.com/index.php?topic=1996

:thumb:

Mark

 

[FotisGR]

Thank you very much. This is what i will do... :thumb:

Cheers
fotis

 

[Michael Krusch]

Vu meter do not need + and - signs, so I don't think that this is a real vu one.

 

[gyraf]

But many real VU-meters (like the Sifam) still have + and - signs on the case, as they are often manufactured in the same cases as dc-reading meters.. You need to check with AC to be sure..

Jakob E.

 

[FotisGR]

You could always build NewYork Daves test oscillator

I try it but doesn't work for me. I can't take 400hz output. No out at all.
I tried it 2 times but doesn't work. The #344 is a led? I tried with led ( psitive and oposite mount) but nothing...

Cheers
fotis

 

[Mark Burnley]

Hi Fotis,

A #344 lamp is a small 10V low current incandescent bulb. You could try a bulb between 6 and 12V in this application. It basically acts as a limiter in this circuit- as the current increases through it, it's resistance increases, therefore lowering the gain of the amplifier stage.

:thumb:

Mark