I've been playing around with some comparator chips, trying to create a working LED VU meter. This is my 2nd attempt. My first attempt was frustrating so I abandoned it.
This time, I played around with values of the capacitors and resistors so the response/speed of the LEDs are to my liking, and added current limiting resistors so the load to the PSU is very light. (Note: Red LEDs are the most "green" LEDs, consuming as little as 5mA of power.) I also learned a few tricks that I think if I have applied it to my 1st attempt, it might have been a success.
The VU meter is composed of (5) LEDS, with dB range from -13 dB to +17dB. The 3rd LED (i.e. the middle LED) is the 0dB mark.
The current for the LEDs is regulated, so the LEDs light up with the same intensity, regardless of the PSU voltage fed to it... which can be anywhere from 3+V to 16V. The max voltage rating of the chip is 18V, and I just connected it directly to the PSU-1848 and so far, it's working fine.
I added a trimmer to help you calibrate the 0dB mark of the LED VU meter.
I've tested the VU meter connected to the PSU-1848 and SC-1 and happy to say... no change in sound characteristic of the SC-1 even though I didn't use a buffer.
I tried connecting the VU meter input to the HOT (Pin2) of the XLR output, and at the INSERT jacks of the PCB, and either one works just fine. The sound of the SC-1 isn't affected. So that's good.
Now the big question now is... where can I use this? There is no more space on the PCB of the IO-module to add this LED VU meter.
I'm thinking, maybe, use this LED VU meter on the upcoming "API" type module preamp. .... there'll be plenty of space on the motherboard PCB, since the rest of the stuff will be located on the external IO-module PCB.
So that's the plan... Check this out.
See... they have a 7-LED VU meter. I'll have a 5-LED VU meter on the new preamp.