4 comparators can easily switch 4 strips of LEDs with a transistor on the output. And since comparators can be used for very small signals and medical equipment, they will not affect the sound quality.

The whole purpose of adding a ring of LEDs around the control know is to have a fancy pointer indicating where the knob is set. If the purpose were just for decoration then there would be no reason to have any control electronics at all, just a bunch of LEDs wired to illuminate. So the complexity of the installation is controlled by what the goal of the project is. If it is only for show, then nothing beyond a string of LEDs, and no useful information, either.

 

4 comparators can easily switch 4 strips of LEDs with a transistor on the output. And since comparators can be used for very small signals and medical equipment, they will not affect the sound quality.

Why would you use 4 comparators (yielding only 4 distinct output levels,) when the aforementioned 3914 family of chips provides 10 distinct levels with far fewer external parts required?

As for sound quality, neither the 3914 family, nor your proposed comparators, will take the AC audio signal directly as an input. You'll need a rectified and filtered DC signal derived from the audio. In order to avoid loading the original audio path and impacting sound quality, you'll probably need an op amp buffer circuit between the raw audio and the rectifier/filter circuit.

 

Actually, maybe you can drive the LM3914 family directly with your AC audio signal. Inputs are good to +/-35V! I should read more carefully before posting...

 

After going back to the original post I see an error of mine, which is that the desire is for VU meter type of display with a control in the middle. The video shows a 16 segment display, and a whole lot of fancy functions which tell me that it is not a simple volume control in the middle. So much for anything simple! The old National semiconductor applications notes include detailed circuits for VU meters, using either one or two of the LM3914 IC devices, along with good explanations of exactly how to calculate the resistor values. AND the app notes also mention how to apply the audio. So there is the solution, well engineered and available via a web-search for the National Semiconductor applications notes.

Avoid the similar sounding "National Instruments" site, that company sells really expensive stuff.

 

Seems that OP has made only one post.

 

OK, now that I correctly understand the requirement, the display and the volume control are totally separated. There are a lot of different LED VU indicator IC devices available, although driving a string of 16 LEDs will need a lot of wires. And the problem of linking the display to the knob ceases to exist. I think that there is a circuit posted on the "Schematicsforfree" website, I don't recall which caregory it is in, though.