Hi Zaik
Stereo blend is commonplace in radio reception even today; basically the high frequencies are progressively blended as signal to noise ratio deteriorates. This is easily accomplished via the switching of progressively larger sizes of audio blending capacitance across left + right channels. The larger the cap, the lower the audio frequencies that are blended.
You can probably fabricate an add-on switchbox connected via a tape loop to accomplish this. Use decent quality cabling, capacitors, & hardware of course. If you want to actively buffer the signals for isolation & a better impedance match, vs. taking a minimalist passive approach, then use at least high quality low noise j-fet op-amps if not good discrete circuitry. A sophisticated power supply is also recommended if going active. I'd suggest trying the passive approach initially just to see/hear how it works out.
Stereo blend is commonplace in radio reception even today; basically the high frequencies are progressively blended as signal to noise ratio deteriorates. This is easily accomplished via the switching of progressively larger sizes of audio blending capacitance across left + right channels. The larger the cap, the lower the audio frequencies that are blended.
You can probably fabricate an add-on switchbox connected via a tape loop to accomplish this. Use decent quality cabling, capacitors, & hardware of course. If you want to actively buffer the signals for isolation & a better impedance match, vs. taking a minimalist passive approach, then use at least high quality low noise j-fet op-amps if not good discrete circuitry. A sophisticated power supply is also recommended if going active. I'd suggest trying the passive approach initially just to see/hear how it works out.