Project files: Audio meters

What is it?
Two designs for audio level (VU) meters. One is a driver for analogue VU meters based on this design.
The other is a small VU meter based on the National/TI LM3916 VU-meter IC. This design comes from here and incorporates a peak-detector with (adjustable) hold.

How big are the boards?

  • Analogue driver: 1.95″x1.625″ (app. 50×41 mm.)
  • LM3916 meter: 2.175″x1.275″ (app. 55×32 mm.)

What is the status of the boards?
The analogue driver board is in version 1.1. It has been built and tested and looks to be working (only a quick functional test, nothing extensive). I have made some cosmetic fixes (silkscreen etc.) for v1.1.
The LM3916 layout is in version 2.1. It is a revision of an old design of mine, so was upgraded to v2.x. I built and tested v2.0 and then fixed a couple of mistakes (including an unconnected power rail – doh!) to get to v2.1.

Does it use any special/expensive/hard-to-find parts?
Not really. The 10-segment LED matrix for the LM3916 circuit is available in both bicolor (red/green) and tricolor (red/yellow/green) versions that match the audio indication levels of the LM3916, but they can be a bit hard to find. I believe they are made by Kingbright and they typically show up on ebay – i honestly can’t remember where I bought mine, but it was probably there 😀

Anything else I need to know?

  • Due to the peak detection circuit, the LM3916 circuit isn’t likely to work with the LM3914 (linear scale) or LM3915 (“standard” log scale) ICs. If this is what you want, have a look at the respective data sheets and google – plenty of other designs out there then 🙂
  • The LED matrix should be mounted on the back of the PCB, but then the board should be reversed for mounting on a panel. The gives the correct orientation for a multicolor matrix as well.
  • You should note that the analogue driver is designed with a balanced input.

Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Please refer to the respective design articles and to the data sheet for the LM3916 IC for additional information.



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