NA523/1 identification needed

Hello,
can someone identify which phono boards are these? S, K, E or R? Looks like S but I’m not sure…If they are S are they ok with medium compliance 15 um/mN mc cartridges like ortofon quintet series? Or should i look for NA523E boards?
System is : Nac 102 & 82 /Nap 180
Linn Sondek LP12 with akito tonearm (serviced with new circus bearings, valhalla power supply and new linn motor)


They are NA523S boards for low output MCs.

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Thanks for an answer Richard. So, they will not work well with 15 um/mN mc cartridges? Better to go with NA523E?

It depends on the output voltage of the cartridge. With which cartridge are you wanting to partner the boards?

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Ortofon quintet red

I see Ortofon quote an output of 0.5mV so ideal for the NA523S boards

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Thank you very much Richard. That was very helpfull!