In regards to an analog VUmeter, are they based on changing amp's? Like the LED based VUmeters, does it go up and down based on how many amps is going through the line? Also, then could you use a needle based amp meter to the same effect as an LED based one? Its probably more complicated then this, but just wondering.
Proper analogue vumeters take an audio frequency AC signal, and, to quote one spec I've got, 1.228v AC produces a reading of 0VU. With a basic moving coil panel meter you can alter the range to whatever you want by adding a suitable series resistor (for volts) or parallel resistor (for amps). To replace a 3914 led meter you'd add the series resistor. So no problem. If you need details for a particular meter, quote us the coil resistance and full-scale (fsd) current.
Ahh, I might try it sometime then, I don't have one currently, but I'll put one on my next order of electronics stuff. Thanks!
if i understand this correct you saying i could simply wire 2 VU metres up to a 3.5mm jack for left & right & plug it into my soundcards headphone port (i dont use it as my amp is connected to the line out) & the most i would need was a couple of resistors on the way incase my headphone socket is makign them jump allover the place?
You need to connect them via a diode. The only problem with this is that diodes have a 0.7V drop across them so your 1.2V line level all of a suden becomes 0.5V, and will only display the biggest peaks in the music. If anyone has a link for the circuit to drive one properly I would be interested too.
Hey Floydian, check this out: http://www.allelectronics.com/cgi-bin/category.cgi?category=385&item=MET-60&type=store Under two bucks a throw, yeehaw. As I understand things, you need to rectify the audio signal (JazzXP, it is AC, and it does go negative) since the d'Arsonval meter movement (this is what pretty much all analog meters are built on, whether they are configured to meter voltage or current, the movement itself responds to current) only measures current in one direction. It wouldn't last long hooked directly to AC, even small currents would damage it. Google for "d'Arsonval" if you're curious for more on how it works.
Supposing this is possible, could you hook up two VU meters in parallel (one LED and one analog), then line up a LED vumeter with the corisponding spots on your analog VU meter, so the LED's light as the pin flies by them? <gets more ideas he can't try yet>
Yep sure could. The LM3914 can be set in dot mode so only the led directly under the needle will be lit, or bar mode so all the leds up to the needle are lit.
If you have problems with too low signal levels because of the diode.. Then why don't you just build a simple amplifier. A schottky diode only has 0.3V forward voltage drop... might be an alternative.
Are we talking a full or half wave wave rectifier for a direct link to the sound card output here and would just a simple class A, single transistor amplifier be all that was needed to bring the levels up to a readable output? Moving coil meters for this sort of thing do have a certain something over an LED bargraph type thing I think /*edit*/ oops sorry for necroing the thread, didn't realise when the last post on it was
There's a fairly simple op-amp circuit that has the rectifier in the amplifier's gain-setting feedback loop so diode voltage loss is eliminated. You can also add a capacitor across the output to give a slower-reacting, average-reading result or leave it out for peak readings. IIRC LM3914/5/6 datasheets have examples.
