Audio volume levelling / AGC for spectrum analyser
My suggestion is to abandon the expensive analog front-end in favor of a software implementation of the spectrum analyzer.  Adafruit has one project, and there are a bunch out there waiting to be found on your favorite search engine.

Since you're building the whole preamp, I assume you have access to a dual voltage supply (\$+V_{cc}\$ and \$-V_{ee}\$).  Therefore, you can pick off the audio, send it through an op-amp buffer, add a DC offset, and send the signal to the Arduino's ADC.







simulate this circuit &ndash; Schematic created using CircuitLab

Here you're still using one Arduino pin for input, but you're shaving several dollars (and shipping days) from the fancy front-end.  Any amplification can happen at the software level if needed; even though the FFT and other maths may be computationally expensive, the analyzer doesn't need to be (and shouldn't be) updated quicker than about 10 Hz.