I would like to have it set up so the average amplitude of the audio for its frequency band dips below a threshold value and then rises above it to create a clock pulse?

OK, so the inverters are acting as comparators, or level detectors.

Next, the outputs. CMOS parts are not known for outstanding output current. They should be good enough for a proof of concept, but in an automotive environment, the LEDs might not be bright enough for you.

ak

 

I want something very similar to this

You should understand how that particular setup works and how it differs from your goal.

What it does is to take a monotone input, count its zero-crossings through the counter, and light up the corresponding leds.

Compare that with your goal.

 

You should understand how that particular setup works and how it differs from your goal.
What it does is to take a monotone input, count its zero-crossings through the counter,

Don't think so. If that were the case all LEDs would come on with every string pluck. For the lower volume plucks the counter advances only 1 or 2 counts.

ak

 

in lieu of 30 different fader circuits, I would like to use a single fader circuit on the common ground of each color group of LEDs.

The more I think about this, the more I think you should build the circuit with no faders of any kind, see how you like the basic dynamics, fiddle with the gains and detection levels and time constants, and get than part set. Fade effects always can be added to the output at a later time, and are an unnecessary complication of getting the display dynamics right. IMnsHO

ak

 

Thanks for the input all. I have opted to scrap the whole thing and go with Arduino sequenced lights.

 

It doesn't have to be an arduino - or a mcu - though it can be done that way.

Basically, think about a 1-band led display. All you do is to rectify the input signal (of sufficient swing) to produce a slow-varying DC signal that reflects the input signal's magnitude. That signal is then used to control the led bar -> how many or which led to light up.

The first part is a rectifier - simple.

The 2nd part is essentially a comparator / set of comparators or logic. For example, you can compare the input signal to a set of reference voltage levels and use that to light up / turn off leds. That's basically what a lm3914/3916 does, or your arduino will do.

But you can implement it differently if you decide to use different parts. Here is an example of implementing a four-led bar through logic gates.

R5..8 is your load - in your case, leds. U1..4 act as four comparators that compare input signal vs. their logic low threshold voltage. the input signal is divided up by the divider R9..13. As you can see through the simulation, the current through R5..8 varies with the input signal: R5 turns on first, then R6, R7 and R8 turns on the last.

By adjusting R9..13, or selecting the types of the logic gates (thus selecting Vilow) you can determine the exact points where an led will turn on / off.

This is just to show that once you know what you want, you can implement it around the parts you have.

Hope it helps.

 

I put this together to give you a sense of the variety of solutions that you could use.

Here is a mcu-based solution. The 12f675 adc's two channel input signal (magnitude), and drives three shift registers to turn on / off 12x2 leds. The leds can be light up in either bar pattern or dot pattern, depending on the logic state of GP3.

In this particular shot, we are display two values, 240 on channel 1 and 2 on channel 2. 240 is displayed as 0xff and 2 is displayed as 0x03, both in the bar pattern. The implementation is essentially a LM3916 in 12-bit format.

So if you were to use something like this, you would then band pass the incoming audio signal, rectify it to produce the needed magnitude information, and use that to drive two of such set-ups. With an avr, you can easily adc 3 channels and drive three shift registers to produce 8bitx3 patterns. And if you pwm the OE pins of the shift registers, you get to control the brightness of the leds.

the point is not that you should follow this particularly design, but to show how different designs can be realized based on your skills and parts.

Hope it helps.

 

BTW, the refresh rate is about 200hz so a lot more can be done here, even with a super slow mcu.