I have just succesfuly constructed the k4305 dual VU meter kit and installed it into my pre amp.
It is used before an active crossover which then feeds 4 gainclone amplifiers.
Now, on clear parts of songs, the LED’s can be heard switching on and off through the speakers.
So far, I have built a seperate PSU for the VU meters (same xformer and bridge as the xover psu, but separate 12V regulator, smoothing caps etc) but the issue is still there.
Disconecting power to the VU meters gets rid of the fault.
Any suggestions would be welcomed or I can supply further details.
First time this issue is reported.
Did you try with a completely separate supply (e.g. battery or wall adaptor) ?
Most likely a ground problem e.g. when current from the VU meter shares audio ground
Star grounding usually solves this issue.
I did try a bench power supply and was greeted with lots of 50hz hum! So havent gone any further down that route.
I was warned by the manufacturer of the active xover that LED’s will almost certainly cause noise when switching if they shared the power supply, hence my attempt at separate regualtor/smoothing etc.
The whole system is in monoblocks where the main psu’s are in sepearate cases to the circuit boards making star grounding pretty difficult, there is no noise in the system though.
Any quick tests I can do with wire jump leads to further diagnose the issue?
No star grounding is almost a guarantee for troubles.
Did you try connecting a battery direct to the board?
This will reveal if the problem is caused by the wiring or if the interference is radiated into the audio circuit.