OK, I understand the M78S is really a stereo cartridge, but how do you wire it for mono playback. My turntable has the standard stereo 4 wires (L, LG, R, RG). For now, I just have one channel wired and have the amp set up to play 2 channel mono.
Which channel plays the vertical in the groove and which channel is horizontal (for mono 78's). I'm looking for the least groove noise.
Some 78 RPM records were modulated in the vertical plane; some in the horizontal plane. The M78S is very compliant in both planes and will play either type of record well.
There is no "correct " answer to your question. Which wiring scheme works best may be different from record to record. Try this order: 1) Left and Right channels in parallel; 2) Left channel only; 3) Right channel only. Use whichever provides the best sounding result.
The M78S works well for 78 RPM records for one main reason: the large radius of the diamond tip. The groove width of 78 RPM records require the stylus tip with a minimum radius of 2.0 mils. The M78S is 2.5 mils.