[Elecraft] KX-1 - cleaning up the squarewave sidetone?

[J]

I did not want to reinvent the wheel, and hoped some mods existed to clean
up the KX-1 sidetone.

At times, I find it difficult to zero in on a station's 600-hz with my "600
hz" squarewave.

Has someone come up with a mod?

 

I'm thinking that plenty of audio is available at the sidetone level setting
(STL), so it might be possible to make an RC filter.

 

It looks like the sidetone enters AF amp via a 1M resistor, R15, to IN1 and
IN2

 

Thanks