Galaga (which happens to be one of my faves from my youth) turned out to be the loudest.

So I just threw my super convenient Xminilab Portable scope (affiliate link) on it, and wired in a 100K potentiometer to manually find the the point where the signal into the amp wouldn't exceed the clipping voltage (see prior post). If you don't know, you don't just wire the pot as a resistor, you connect both the signal wire and signal ground, to create a voltage divider. Sometimes a voltage divider in an audio usage is referred to an L-pad (because of the shape of the schematic) but often that's only used for speaker-level control, it seems.

This worked: R1 = 65.5K, and R2 = 27.2K, for a R2 / (R1 + R2) ratio of 0.293. I suspect the amp's impedance was having a significant effect.

That worked out well but I found a weird effect, if I turned down the volume too low (R1 = 88K and R2 = 5K) I would get a weird "machine gun" effect over the audio. Listen here:

This is where I admit I'm not so good with AC circuits....

So my next thought was if R2 was too low so I tried putting a number of different resistors in series with R2, but while that seemed to work, it also prevented it from getting very quiet. So I increased R1, which again led to "machine gunning" at low levels, so I increased R2 again, and so forth. Some EE is probably laughing at me right now... but after a bunch of experiments I realized I couldn't both minimize the volume on one end *and* maximize the volume on the other end.

To complicate matters I didn't want to use the full-size potentiometer I was experimenting with so I popped over to All Electronics and found something suitable (see main completed image) but not exactly what I wanted. What I wanted was something like the volume control you'd see on an old transistor radio.... but I didn't know until later that's called a Thumbwheel Pot.

That pot turned out to be 150K (actual 144K).

For best loudness without distortion at low end:

• R1S (in Series with R1) = 150K (146.7K actual) and R2S = 18K (17.49K)

For best softness although giving up max loudness:

• R1S = 500K and R2S = 4.3K (No actual values recorded)

So I went with the later... next to choose which speaker.