Rek-O-Kut VU Meter documentation

[basplin]

Hi all - I found a really cool Rek-O-Kut VU meter off of 'the auction site' a little while back and I'm wondering if any trolls might have installation documentation for it, or have any idea how I might go about installing this in my signal chain. If I can install it like any other VU meter, I know there is plenty of information out there and I'll dig into that, but I guess I'm really wondering if anybody knows if there is something special about this one and should be treated differently. Thank you all in advance!

[markrob]

Hi,

I see it is a rectifier type which means its AC responding so you should be able to strap right across the head providing the scaling matches. On the back, I see the number 500. I think that might be the designed impedance. It shows 0dB = 6mw. The best bet is to connect it to a signal generator or power amp and feed a 1Khz sine to it. Determine the RMS voltage needed to reach the 0dB mark on the meter. At 500 ohms, that equates to 1.73 Vrms At 8 ohms, 0.220 Vrms. (R = V squared * 0.006 mw) Using an external resistor, you should be able to scale it to a different reference as needed.

Mark

[basplin]

Hi Mark, thanks for your reply. By hooking it up "across" the head, do you mean in parallel, as in the photo (if I am using 8ohm)?
This is helpful information, thank you!

[markrob]

That looks correct, but you should test carefully using a signal generator and an AC voltmeter to see if where the 0 dB reading is at. Also not sure what the other terminal is for. Perhaps one terminal is 500 ohm and the other is 8 ohm, since the meter has both scales.

[basplin]

That's what that looks like. Seems like 500ohm was also a common cutterhead impedance back then.
Dumb question - does adjusting the input level of the signal have an impact on the output amperage from the amplifier?

[markrob]

If this meter was designed to connect parallel to the head, it would not cause any significant additional loading. Its really just measuring the AC voltage at the drive coil just like any analog voltmeter. Its also possible that it was designed to be located at the input to the power amp (line level) and would have been scaled to match the reference level shown on the dial face. If you know what model Rek-O-Kut it came from, you should be able to figure out how it was used by looking at the schematic. Without that, you will have to make some measurements to nail this down.

I also was thinking that one of the terminals may be for a dial lamp.

Mark

[basplin]

Thanks for this info! Good question on the RekOKut model this came from, that I do not know. I've seen ad's for standalone VU meters that they sold, and this very well could be one of those. I've never seen one installed in any of their amps, and the meters that are in their amps look different than this one. If it was sold as a standalone, it very well could already be scaled as you mentioned. When you mention "located at the input to the power amp (line level)" you mean basically metering in the input signal, right?

[markrob]

Yes, monitoring the input signal.

Let us know what you find after playing with this.