Anyone have 'stereo blend' control experience?

My long gone Dynaco PAT4 preamp had stereo blend but I can't remember exactly what it was for. Maybe for their three speaker with center channel application that was supposedly specially suited to the Dynaco A-25 speakers. Whenever I used it in two channel I had the eerie feeling it was neither stereo nor mono and that made it seem strange. It wasn't progressive, just on or off. I'll betcha somebody has the circuit diagram for a PAT4 and the directions for building one underneath a pile of old stereo reviews. Good luck in your search.

The PAS 3x blend control was especially handy when listening over headphones.

Bob P.

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.