Johnny, As I thought I clearly stated, I am not arguing at all that playing mono LPs in mono mode, no matter how it is arrived at, is not optimum. In your last paragraph, you seem to be talking about a condition that I have not even dreamed of... playing a stereo LP with a mono cartridge. (I could be wrong about your intent.) Let's leave that out of the picture as a generally bad idea.
To repeat, many if not most modern mono cartridges are internally constructed as stereo cartridges, except that the outputs of the two channels are summed prior to exit. Such cartridges will likely be responding to vertical modulation imparted by the record grooves. Of course, on a mono LP, there is no music encoded for vertical modulation, but there will be some spurious noise which is cancelled prior to the output connections. When you use a mono switch on a preamplifier, exactly the same thing happens. Thereby, mono LPs played even with a stereo cartridge will sound much better than if played back in stereo. What I am wondering about is whether in fact it makes any important audible difference whether one uses a mono cartridge or a mono switch to play back mono LPs. I don't say that I know the answer; I am just curious. There is a well known guru on Vinyl Asylum who insists that the two methods are indistinguishable sonically. I am never as certain about anything as he is about everything.
To repeat, many if not most modern mono cartridges are internally constructed as stereo cartridges, except that the outputs of the two channels are summed prior to exit. Such cartridges will likely be responding to vertical modulation imparted by the record grooves. Of course, on a mono LP, there is no music encoded for vertical modulation, but there will be some spurious noise which is cancelled prior to the output connections. When you use a mono switch on a preamplifier, exactly the same thing happens. Thereby, mono LPs played even with a stereo cartridge will sound much better than if played back in stereo. What I am wondering about is whether in fact it makes any important audible difference whether one uses a mono cartridge or a mono switch to play back mono LPs. I don't say that I know the answer; I am just curious. There is a well known guru on Vinyl Asylum who insists that the two methods are indistinguishable sonically. I am never as certain about anything as he is about everything.