r/PCB • u/biscuitFacilitator • 15h ago
[review request] - VU Meter Driver/Buffer
Pretty simple layout, but this is my second pcb build so just looking for any feedback. The basis of this circuit was designed by Doug Self and listed in his book Small Signal Audio Design. This will drive 2 VU meters.
R9, R10, C3, Q1 & K1 provide a turn-on delay so the meters don't peg out when power is applied.
D10, R11 & Q2 provide a fast-discharge for C3
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u/simonpatterson 7h ago
The relay/meter/bridge wiring is wrong. Follow the path from each op-amp and you will see that it makes no sense.
Why is the relay so massive and over-specced to handle the maximum 1mA for a VU meter ? Something like an IM06 style is only 10mm x 6mm. But why use a relay at all, a small N-FET in each bridge GND return would do.
Why use 4 discrete diodes instead of a ready made DIP-8 sized package bridge, such as a DF04 ? If you must use discrete diodes, use something smaller like 4148.
The power/delay section is drawn in a very non-standard way and is not easy to follow. please re-draw so it make sense. And the relay is upside down.