How are you playing your precious MONO Vinyl?

My point is that the absence of a Microgroove label on a post-1948 LP does not necessarily mean the LP doesn’t use the 0.7mil groove width.

@lewm We don’t know.

A multi-EQ preamplifier is not strictly necessary to play mono records unless those records are from the pre-RIAA period. And if you want to play 78 RPM records, you'll not only need a multi-EQ preamp, you'll also need a phono cartridge with a larger profile stylus, like 3 or 4 mil, as opposed to the .7 to 1 mil used with mono LPS. In my all-mono system (single amp, single speaker) I have two Miyajima MC carts, one with .7 mil stylus and the other with a 4 mil. stylus. I swap these in and out with my Jelco arm with removable headshells. I am currently using a Graham Slee Revelation C for phono preamplification, but Sun Audio, Tempo Electric and other multi-EQ phono preamps are available for that purpose. Esoteric/Rek-O-Kut also offer a clever "re-equalizer" for your standard stereo preamp that will not only offer you every possible EQ curve but will also allow you to dial in true dead-center mono with your stereo system. I have not heard it, but an earlier version got good reviews in Stereopile and it's quite reasonably priced.

Now, when playing regular RIAA mono LPs (33 or 45 rpm) there is no substitute for a true mono cartridge (as opposed to a strapped stereo cartridge or using the mono switch on your preamp. Mono cartridges have more life, better dynamics and no phase problems.  I have a stereo system in my living room which uses a wood-bodied Grado stereo cartridge and its identical true mono sister.  I have the two Grados on matching headshells and I swap these in and out of my SME arm. The mono has the same two pairs of pins as the stereo pickup but are connected to the same coils, so have identical output. I play both into a regular stereo preamp and never touch the "Mono" switch. One important difference between my Grado and Miyajima mono cartridges. The Grado has some compliance in the vertical plane so stereo records played on the mono Grado would not be damaged, whereas the Miyajima has no vertical compliance so could damage a stereo record. For this reason no stereo records enter the all-mono room.

@vinylrestingplace 

Thank you for your comprehensive summary of what’s required for high-quality mono and 78 RPM playback. You’ve outlined several key nuances that some of us may overlook or those newer to mono playback. 

Congrats on building a thoughtful and deliberate mono system, the kind that lets you hear records from 1948 to today as they were meant to be heard.