Single Section Bandpass Filter driven by the 2 Transistor Audio Oscillator

Using the "right side" of this circuit:

https://wb9kzy.blogspot.com/2025/01/a-two-transistor-sine-wave-oscillator.html 

I tried a single section bandpass filter:

The values are from a design I had used previously with a four section opamp filter.  I had raised the cap values and lowered the resistor values to minimize noise.  The gain and Q are both low as that's the standard rule of thumb in ham radio.  I did notice a lot of interaction between the filter and the oscillator (600 Hz was the lowest frequency with the filter while before it would oscillate as low as 482 Hz).  A higher impedance buffer is called for here ?  But the circuit does seem to filter, the waveform looks less bumpy :)

top: 2 transistor oscillator, bottom: single section filter - the filter circuit does invert

it *looks* like a sin function to me :)

This was a quick try of a single section on a solderless breadboard - I may try a 4 section filter (the usual configuration for this type of circuit as a CW filter to see how it compares with an opamp version.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm