Wiring a VU meter

[danielzink]

Hey all,

I've seen a couple of amps lately (ie: ashdown) that have VU meters wired into them.

Anyone have any experience doing this ?

I have a couple of "project" amps that I'm always fooling around with and I think it would be a hoot to have a big ol' VU meter mounted on one of them.
Whether it does anything functional is beside the point. The fact that the needle would move and the meter wouldn't affect the sound the amp in any way are the primary concerns.

I was wondering what kind of meter I would need and where it would be wired into ?

Thanks, Dan

[chocopower]

Hi there!!

i was looking for something similar... maybe those ones....

http://es.farnell.com/jsp/search/res...isGoback=false

[danielzink]

i was looking for something similar... maybe those ones....

http://es.farnell.com/jsp/search/res...isGoback=false
Today 09:39 AM

mmmmmmmmmm....not really...

Your link shows all digital meters.

I'm trying to wire in something more along the lines of these:







Thanks, Dan

[Old Tele man]

...just remember that most (but not all) VU-meters assume a 600-ohm source load, so you're probably gonna have to come up with a voltage-divider circuit having a 600-ohm resistor in either the "top" or "bottom" postion.

[danielzink]

...just remember that most (but not all) VU-meters assume a 600-ohm source load, so you're probably gonna have to come up with a voltage-divider circuit having a 600-ohm resistor in either the "top" or "bottom" postion.

That's the kind of info I'm looking for.

Any ideas on how to do that ?

[Ampclutz]

Many old tape recorders had VU meters. Maybe you could find something by looking at those schematics and layouts.

I have an old one somewhere around here that has VU meters.

AC

[petemoore]

http://sound.westhost.com/project55.htm

[Enzo]

I think if you have a piece of equipment called a VU meter, that 600 ohm thing might pertain, but in the circuit, it is just a voltmeter. True VU meters have a controlled ballistic response to the needle, but that is mechanical rather than electrical. The stuff on amps today is just eye candy. it takes nothing much to drive it, so try a low voltage meter. AC volts for direct drive from a signal, or you could rectify the signal and drive a DC meter. For that matter you could certainly steal a meter from a dead tape deck or something similar, then it would already have the VU scale printed on it.

SInce you want it for decorative reasons, who cares how accurate it is?

[Steve Conner]

I put meters on all my homebrew amps! I like to have it reading the cathode current of the power tubes, because that's actually useful.

What I do is connect a resistor of 1 ohm or so between the tube cathodes and ground, and connect the meter across that. I add another resistor in series with the meter, to adjust the scale, and also to give it a little protection in case a tube shorts out. Though if the 1 ohm resistor blew open, I doubt anything could save the meter, so I use an oversize power resistor there too.

BTW, the ballistics depend on the source impedance of the electric circuit, too. If you drive a VU meter from a circuit with higher than the rated impedance, the needle will overshoot more. A short circuit gives the highest mechanical damping, and some people recommend shipping meters with their terminals shorted to stop the pointer flailing around so badly.

[bob p]

A short circuit gives the highest mechanical damping, and some people recommend shipping meters with their terminals shorted to stop the pointer flailing around so badly.

fwiw, I transport speakers with a shorting plug in place.

[Steve Conner]

[Old Tele man]

...from Wikipedia:

"Volume Unit (VU) defined: The reading of the volume indicator shall be 0 VU when it is connected to a 600-ohm resistance in which is flowing one milliwatt of sine-wave power at 1000 cycles per second."

"In professional audio, a popular unit is the dBu (see below for all the units). The "u" stands for "unloaded", and was probably chosen to be similar to lowercase "v", as dBv was the older name for the same thing. It was changed to avoid confusion with dBV. This unit (dBu) is an RMS measurement of voltage which uses as its reference 0.775 VRMS. Chosen for historical reasons, it is the voltage level at which you get 1 mW of power in a 600 ohm resistor, which used to be the standard reference impedance in almost all professional low impedance audio circuits."

...also explained in most collegiate electronic textbooks.

[danielzink]

This is all great - but in the spirit of my original post.

Man......I just really want a needle that moves up and down in relation to something within the amp.......

It doesn't even have to mean anything......


Dan

...from Wikipedia:

"Volume Unit (VU) defined: The reading of the volume indicator shall be 0 VU when it is connected to a 600-ohm resistance in which is flowing one milliwatt of sine-wave power at 1000 cycles per second."

"In professional audio, a popular unit is the dBu (see below for all the units). The "u" stands for "unloaded", and was probably chosen to be similar to lowercase "v", as dBv was the older name for the same thing. It was changed to avoid confusion with dBV. This unit (dBu) is an RMS measurement of voltage which uses as its reference 0.775 VRMS. Chosen for historical reasons, it is the voltage level at which you get 1 mW of power in a 600 ohm resistor, which used to be the standard reference impedance in almost all professional low impedance audio circuits."

...also explained in most collegiate electronic textbooks.

[Old Tele man]

...simple "wiggle-meter" can be either:

(a) a hi-Z voltmeter (so it won't load down the signal path) at input to PI

...or...

(b) a milliampmeter (with small shunt capacitor to 'smooth' out the "crest-factor" peaks) in cathode of output tube(s).

[danielzink]

...simple "wiggle-meter" can be either:

(a) a hi-Z voltmeter (so it won't load down the signal path) at input to PI

...or...

(b) a milliampmeter (with small shunt capacitor to 'smooth' out the "crest-factor" peaks) in cathode of output tube(s).