How are you playing your precious MONO Vinyl?

“I’d say that in this case, everything hinges on the design and sound quality”

@goofyfoot 

Exactly, the value of a two channel mono phono preamp comes down to design execution, sonic character, how it complements my system’s voicing and not some theoretical advantage from its dual-mono nature alone. 

My current phono has ONE input. If I don’t hear any audible advantage with EQ-100, I may upgrade to a high quality stereo phono preamp with TWO inputs and that would be the end of my phono quest for a foreseeable future. 

A "two channel mono phono preamp" is any phono preamp or phono driving a linestage where the mono mode is engaged, when you feed that phono section with a true mono cartridge. Lalitk, I don’t understand exactly what you are after. If you want to go the ultimate purist route, then use a true mono cartridge with only two pins for output driving one channel of a stereo phono stage which in turn drives one of the two amplifiers driving one of your two stereo speakers, like Elliot says he sometimes does. The added advantage of the EQ100 is only the ability to select the compensation curve. If you don’t know for sure what pre-emphasis curve was originally used, then fiddling with the de-emphasis curves is pure guesswork. You might find one curve that pleases you most, but you cannot be sure it is the algorithm that was actually used in the making of the mono LP. I’ve got one set of mono LPs, Louis Armstrong and Ella Fitzgerald, the classic recordings, on EMI in mono (UK pressings), where when you play them with RIAA filtering something sounds off.  Whereas the original US pressings on Capitol (I think, or maybe Verve) sound wonderful with RIAA filtering.  I have always suspected that the EMI pressings were done differently in some way.  Of course, no matter what, the music is sublime.

@lewm Sorry to verge off topic a bit but weren’t the grooves in the mono micro groove pressings wider than the stereo grooves but more narrow than the original mono grooves?

Not a groove expert. I only have read what I wrote, which only applies to the 33 rpm era post ~1948. 

“I don’t understand exactly what you are after”

@lewm 

Let me try to clarify. 

You described how your UK EMI mono pressings of Ella & Louis sound “off” with RIAA EQ, while the US originals sound wonderful. I was just curious: have you ever tried listening to those UK EMI pressings using a different EQ curve, like CCIR or EMI, if you have access to a phono stage with that option (like the EQ-100)?

Sometimes switching to a different EQ curve—by ear—can make those “off” pressings come alive. I’m not suggesting it’s about being historically precise, but rather asking…. have you experimented to see if any other curve actually sounds better to you on that specific recording? 

I recognize without definitive info on the original mastering EQ, dialing in playback EQ is largely educated guesswork. And while something like the EQ-100 offers flexibility with its 10 curves, it’s ultimately your ears not the curve selector that decide what sounds “right.” 

That’s all I was getting at—purely from a listening and enjoyment perspective.

As I said before, EQ-100 is an interesting product and it may lead to new discoveries, such as musical expressions and the performer's intentions that have previously been buried or hidden.