i was at my local electronics surplus shop today and picked up a couple VU meters (they were new and $2, so why not, i need some for the alephs anyways).
well, they have a scale that on the top reads 1 - 100, then to the right of that, a red scale. the bottom readings are -20 to -1, then in the red zone, its +1, +2, and +3.
the brand is modutec, but i dont see a model # and couldnt find one on a website. does anyone know how these things work, or what they measure? can i use it? if not, someone can buy them off me, or i can return them.
edit:
i looked on digikey, and one JUST like it (cant tell if its the same because i dont have this model #), sells for $29 each. so a good deal if i cant get them to work.
well, they have a scale that on the top reads 1 - 100, then to the right of that, a red scale. the bottom readings are -20 to -1, then in the red zone, its +1, +2, and +3.
the brand is modutec, but i dont see a model # and couldnt find one on a website. does anyone know how these things work, or what they measure? can i use it? if not, someone can buy them off me, or i can return them.
edit:
i looked on digikey, and one JUST like it (cant tell if its the same because i dont have this model #), sells for $29 each. so a good deal if i cant get them to work.
I have a circuit for driving a VU meter like the one you describe on my site (under electronics->VU meter), built from information gleaned from this page..
They're pretty simple really: They measure the level of an audio signal, calibrated in a way that is designed to correspond to our subjective perception of loudness. Drive them by rectifying and smoothing the audio signal.
They're pretty simple really: They measure the level of an audio signal, calibrated in a way that is designed to correspond to our subjective perception of loudness. Drive them by rectifying and smoothing the audio signal.
A full-wave rectifier will be more sensitive than a single diode. If you need more than that then you'll have to use some sort of gain stage... probably an op-amp or transistor. Or you might be able to use a small transformer if the source can handle the load.
It might not be necessary though. The ones I have show full scale deflection at a mere 240mV, which a line level input should be able to provide.
It might not be necessary though. The ones I have show full scale deflection at a mere 240mV, which a line level input should be able to provide.
i plugged it in, using a 600V bridge rectifier i had laying around, and it appeared to work fine. it was maybe a bit TOO sensitive. so a guess a resistor could help.
does this circuit, being that it's in the signal path hurt the music any amount? if i throw a whole circuit in there im sure it could, but with just a resistor, the meter and the rectifier, how bad can it hurt it? (im planning on maybe having a switch that switches it in and out of the signal path).
does this circuit, being that it's in the signal path hurt the music any amount? if i throw a whole circuit in there im sure it could, but with just a resistor, the meter and the rectifier, how bad can it hurt it? (im planning on maybe having a switch that switches it in and out of the signal path).
I may be totally wrong on this, but if you were to use a voltage divider to tap off a few mV at the output, it seems to me this would have less chance of a sonic impact than at the input where any disturbance is subsequently amplified. Acuracy might be less since one leg of the divider is the speaker load which is a varying impedance; hence the reading could vary by spectral content even is average votage was constant- but then you said you were not that interested in accuracy anyway.
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