VU Meters

[Nick Franklin]

Hey guys, sorry to make another thread about VU meters, but I couldn't find what I was after by doing a search.

I've just aquired a pair of VU meters from an old tape machine, and I was wondering how difficult it would be to hook the two so I could monitor the main mix outs on my DAW.

I use a digi 002, with my monitors hooked up to the monitor outs (exactly the same as the main outs but with a volume control), so the main outputs are spare for this purpose.

I tried soldering a normal TRS jack to the VU meters (there is a positive and negative terminal on the back of these meters), and plugging that strait into the main outputs. This did make them move, but 0dB FS was only generating a little bit of movement, and occasionally a snare hit or something would cause a wild swing all the way up around 0dB VU. The needle seemed to be moving way too fast for VU aswell.

So I'm presuming hooking these up isn't as simple as that (I presumed it wouldn't be...because off the shelf models are so expensive).

Any advice about how I might go about hooking these up would be greatly appreciated!

Thanks,

Nick

[owel]

Is the back of the meter thick? or flat? Any photos?

I suspect this just an ordinary ammeter labeled as a VU meter.

By tape machine, do you mean a "REAL" tape machine, or home/consumer reel-to-teel tape machines?

Real VU meters have rectifiers at the back, housed inside the plastic thus making for a thick back to house the rectifiers. If yours doesn't have it, then it's probably not a real VU meter. The meter movement is also calibrated, both in rise times and decay.

Real VU meters costs about $50 used and $80-$100+ each new.

There are circuits on the net for making a buffer circuit that is also a full wave precision rectifier to convert meters like this to VU meters. Google them. This will give you a "workable" VU meter good enough for "looks." But still, because the meter ballistics are different, it's not a real VU meter. If you want a real VU meter, you'd have to spend for it. But for that "vintage" look, the buffer and precision rectifier circuit isn't bad... I mean, you just want to see the meters dance, right?.. I assume.

If you'll be relying on VU meters to see if you're clipping, look elsewhere. They're meant to show the "average" and will not be useful telling you if you're peaking and going into digital distortion going into your audio interface.

But for "looks", yeah they bring a certain vintage look into your equipment.

[Nick Franklin]

Thanks for the the reply owel,

The back to these is fairly thin, so I'm presuming they aren't proper VU meters.

I'll google for those circuits, thanks mate.

Nick

[Hugh Robjohns]

Yes, sounds like it's just a meter movement with a VU scale stuck inside. A proper rectifying buffer circuit will sort you out. It might be as easy to track down the schematics for the old tape machine and see what was used in there to drive the meters.

To check the calibration, you'll need to use steady 1kHz tone with a level of -20dBFS (if you are in the US) or -18dBFS in Europe), and then adjust the buffer gain to provide a deflection of 0VU on the scale.

Hugh

[Nick Franklin]

Thanks hugh.

I'm from Australia, I don't suppose you know what our standard in dB FS is for 0dB VU? I pressume we're probebly more in line with the europeans?

Anyway, are there any aussies out there who could recomend me a dealer in Australia for parts and the like?

Thanks

Nick

[owel]

You can measure the voltage.

0dB is equivalent to 0.775Vrms.

[Nick Franklin]

You can measure the voltage.

0dB is equivalent to 0.775Vrms.

Thanks man

[Hugh Robjohns]

0dBu is equivalent to 0.775V RMS

0dBV is equivalent to 1.000V RMS

0VU is generally perceived to be equivalent to +4dBu which is 1.223V rms -- although in fact this is an amusing historical mistake. In reality 0VU was intended to be adjusted to each specific system's (or broadcast or recording company's) standard internal reference level which could be 0dBu, +4dBu, +8dBu or whatever.

I have in the back of my mind that Australia has adopted the SMPTE reference (alignment level = -20dBFS) but I wouldn't take that as gospel.

Hugh

[forumuser695516]

Maplins used to make a kit for this. Basically a circuit specifically for driving an analogue VU meter. Im not sure if they still make it..
I think I still have mine somewhere.. I made a right hash of it, but it worked! Just.. This was a good 15 years ago mind.

Paul