Adding Stereo VU Meters To A Turntable

A pleasing development for those with an interest in audio equipment from decades past has been the recent resurgence in popularity of vinyl records. Whether you cleave to the view that they possess better sound quality or you simply like the experience of a 12″ disk with full-size cover art and sleeve notes, you can now indulge yourself with good old-fashioned LPs being back on the shelves.

[Michael Duerinckx] is a fan of older trance records, and has an Ion Pure LP turntable which is fortunately for him not such an exclusive piece of audio equipment that it can’t be readily hacked. The hack he’s applied to it is a relatively simple one but nonetheless rather attractive, he’s added a set of LED VU meters in a ring round the edge of the platter.

Behind the LEDs is the trusty LM3915, an integrated circuit which will no doubt be familiar to any reader whose earlier life was spent among 1970s and 1980s audio gear. Internally it’s a stack of comparators and a resistor ladder, and it simply turns on the required number of outputs to match the level on its input. He’s put a pair of them on a little PCB with an associated PSU regulator, and mounted the LEDs in a row of holes drilled in the MDF base board of the turntable following the edge of the platter. Power and audio come from the turntable’s circuit board, which contains a preamplifier and the USB audio circuitry. A traditional turntable with a low-level output would not be able to drive an LM3915 directly.

This is a relatively straightforward project and the turntable itself isn’t necessarily the most accomplished on the market, but it’s very neatly executed and looks rather pretty.

Turntable projects are not as common as you’d expect here at Hackaday, but we’ve had a few. There was this concrete example for instance, and a very pretty one using layered plywood.

Courtesy of SoMakeIt, Southampton Makerspace.

8 thoughts on “Adding Stereo VU Meters To A Turntable

    1. It would probably get slightly expensive. Why not rectify the input waveform with an ideal rectifier and use any microcontroller of choice to sample the level and drive the LEDs? Ability to run LEDs multiplexed, to adjust the rise/fall times, peak level display etc comes for free! The LM’s despite being the mainstay of hobbyist world will probably be obsolete in a few years, I would not marry them anymore.

  1. My dear wife insisted we have a working turntable so as not to lose access to our rather extensive collection of LPs, however the occasions either of us bothers to use it are very rare.

  2. Funny how he blames the “loudness war” for his meter over driving. Could it be that it’s not calibrated properly, or he’s got a gain stage in there that needs to be compensated? Of course not. It’s the “loudness war.”

  3. I just reached for my very yellowed and acid paper fragile copy of Forrest Mims’ E N 2 and note the ’15 is log. The ’14 is linear, and the ’16 is “VU” log below -10 or something like that and linear above. No wonder he thinks there is “loudness war” going on. This would be the poorest choice for a visual effect or DJ monitoring. I made several of those and bought more at hamfests. They stack up to 3 without difficulty.

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