Single channel analyzer

[john scint]

Dear Peter,

I see all member's on this forum have spectrometer based on pc from sound cart and theremino software which I worked defore years very good but I would like pcb board or circuit from window comparator and after that point which I can adjust on board the window and board can detect only the one energy which I want at a time.

How can I find that ? I know the Google solution but l must little help from someone