Rega P10/Apheta 3 connected to Luxman EQ-500.

The Rega Apheta 3 has a .35mv output

The setting on your Luxman should be the low ouput MC -"high" setting-63db

" I spoke to luxman and they think I should just set MC high and that’s it."

Luxman gave you correct information.

"I have read posts talking about the effect of the gain dial on MC cartridges(though it is meant for MM primarily."

The gain dial is intended to adjust to whatever cart you wish to use-MM or MC

Thanks for your input tablejockey.

I've had my P10 with an Apheta 3 MC and EQ-500 for over 2 years.  The EQ-500 has 2 controls that affect the overall gain.  One control has 3 settings: MM, MC-HIGH, and MC-LOW.  The other control is the gain control and it has 3 settings: 36dB, 38dB and 40dB.

The MC-LOW (for low output MC cartridges) will give you the highest gain.  The MC-LOW setting will provide 63 dB of gain when the gain is set at 36dB.  If you want the highest gain, you would set the gain at 40dB and use the MC-LOW setting for 67dB of gain.  The MC-HIGH (for high output MC cartridges) setting only provides 55dB at a gain setting of 36dB and 59dB when the gain is set to 40dB.  I'm getting these values straight off of page 11 in the owners manual.

I use the MC-LOW setting and 40dB of gain for a total gain of 67dB.  I could set it lower at 63dB (gain set at 36dB) but I like to have my digital and analog volume close when switching between the two.  If you use the MC-HIGH setting, I don't think you'll have enough gain at any of the 3 gain settings. 

I just tried the setting MC-HIGH and confirmed that it's not the right setting for the Apheta 3.  The sound was muted and less dynamic versus the MC LOW setting.

I have the exact same set up except with P8.

The alpheta 3 has a recommended input load impedance of 100 ohms. According to the EQ-500 manual the input impedance on the MC low setting is 2.5 ohms. Is this a mismatch to be concerned about?

the maximum capacitance setting on the EQ-500 is also 300 pF but the recommended setting per Rega for the Alphets 3 is 1000 pF. Is this a potential issue with sound quality? I have mine set to the 300 pF max.

I am using the balanced out on the EQ-500 and have plenty of gain on either MC low or high. It seems like the 40 ohm indicated for the high setting would be a closer match to Rega Alpheta 3 recommended settings?