G'day all, interesting. My only thought is that if the preamps use a simple one op amp feedback or other design then perhaps the overall voltage gain may be just slightly lacking, givng the results you have observed.
My present DIY phono stage (the ESP P06) has an additional gain stage which is the better approach, in my opinion. Interestingly enough even with this high level of overall voltage gain my M97xE MM cartridge still needs a bit of a volume control push, but the M97xE is known for being slightly low output for a MM cartridge, despite the healthy published output 'specs'.
I suspect that your preamps are ok, just slightly low output. The single stage phono stages I've built all have this 'issue'. Although a single op amp can develop very high gain, for 'quality' reasons the voltage gain is often 'throttled' back a little. Regards, Fap.
My present DIY phono stage (the ESP P06) has an additional gain stage which is the better approach, in my opinion. Interestingly enough even with this high level of overall voltage gain my M97xE MM cartridge still needs a bit of a volume control push, but the M97xE is known for being slightly low output for a MM cartridge, despite the healthy published output 'specs'.
I suspect that your preamps are ok, just slightly low output. The single stage phono stages I've built all have this 'issue'. Although a single op amp can develop very high gain, for 'quality' reasons the voltage gain is often 'throttled' back a little. Regards, Fap.