can I turn my stereo amp to mono- is there a way

Does it have a tape output? Many of these are unbuffered and an interconnect from the R to the L will mono the amp.

Of course, if the LPs are already mono, why do you need it?

Kr4...He needs to go mono because of the LF noise of vertical groove modulation, which has no signal, except the noise.

A jumper from TAPE OUT LEFT to TAPE OUT RIGHT might woek as you suggested, and would be the most easy. If not, use two Y-interconnects, 2 to 1 plugged into a 1 to 2, connected from TAPE OUT to TAPE IN, and select the TAPE input. You will need to get male and female connectors or coupler, as required.

Better yet, put a short across the HI wires from the stereo phono pickup. You could tack solder this across the phono input jacks of the amp, or even put a switch in to give you stereo/mono selection for the phono input.

Eldartford wrote: Kr4...He needs to go mono because of the LF noise of vertical groove modulation, which has no signal, except the noise.

Then he needs a mono cartridge.

Kr4...The so-called "Mono cartridges" that they sell today are, I'm told, nothing but a stereo one with the Hi terminals strapped. (Which was my last suggestion).

Not all. I believe the Lyra mono is a specialised design.

Kr4...Could be. Of course if you want to play 78 rpm records you need a different diameter stylus as well.