That’s really interesting Doity, and quite a co-incidence – I was toying with a design for a similar thing a few months back! I was inspired by those pseudo ‘scope displays that Pioneer put on their quad receivers. Like Sonik said, there are loads of VU boards available either as built modules or as DIY kits you can use for this sort of thing. I used a kit as it was then easier to change the mulitcoloured LEDS to normally fitted to such things to large square green LEDS more suited to mimicking a scope:
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I tried a couple out as shown here with a stereo signal where I’m also experimenting with making a scope style graticule:
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The next stage was to make another two boards and arrange all four in a suitable housing (this was a modified deep picture frame, shown here without the graticule and glass):
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But then, as so often happens (!) I lost interest and moved on to another project so it’s not gone any further. I might get back to it but the real reason I haven’t got much enthusiasm for it now is that it’s not a proper vector-scope display and so doesn’t tell you anything about what’s going on in positional terms between the four cardinal points. You also need to take phase into account to do that of course. So I am thinking about doing this as an addressable x-y array of LEDS. Whether this one gets any further than the prototype stage is, given my track record, problematic!!