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

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?

the input impedance on the MC low setting is 2.5 ohms. 

No it is not.

When Luxman says the MC Low is 2.5 ohms they are referring to the cartridge's internal impedance, not the load the cartridge sees. The internal impedance of the Apheta is 10 ohms.

It seems like the 40 ohm indicated for the high setting would be a closer match to Rega Alpheta 3 recommended settings?

Not necessarily.

The Luxman MC inputs are designed for low impedance ( 2.5 ohms ) and high impedance ( 40 ohms ) cartridges.

Examples of low impedance cartridges are Koetsu's 3-5 ohms, Mysonic Lab 2-3 ohms.

Examples of high impedance cartridges are Denon 103 ( 40 ohms ).

Since the Rega APHETA 3 is 10 ohms, the low MC setting is probably closer to ideal. The Rega needs to see 100 ohms - try measuring the input impedance on the phono to see what the load really is on the "2.5 ohm" setting.

In reality as mentioned above, getting the gain right is as important as load, so nothing wring with trying the different settings and using your ears to decide the optimum settings.

Thanks clarifying Dover. I will measure to get actual on the 2.5 setting.
 

I can’t hear much difference in sound quality between the Low and high MC settings just a bit of gain difference so I will likely run at low as recommended. I have to be cognizant of too much gain in my system as the Cary SLP-05/pass X250 combo has alot of gain even for my relatively inefficient speakers. I am still running through threads trying to wrap my head around cartridge loading and impedance settings and how they are reported by the manufacturers. 

This is slightly off topic, but since there are two or three of you with this set-up, and I’m considering it, can you speak to your satisfaction with, and the qualities of the sound, with the P10 into the EQ-500?

lldd…I have only been using this set up for about 2 weeks but thus far I am extremely happy with this combination. I have not tried a multitude of phono stages. I had been running through the Rega Aria previously. Soundstage is much deeper and highs are smoother and incredibly real. I recently replaced the rectifier with a NOS Mullard and that is still burning in but seems to be a nice addition.

i initially had some concerns about using tubes for both my pre (Cary SLP-05) and phono stage in terms of immediacy and slam. I have not found that to be the case. On good recordings cymbals are crisp and bass tight. Horns and vocals are literally like a live show in terms of prescience and intimacy. ( Kind Of Blue UHQR/ MoFi; Diana Krall Live in Paris/Turn Up The Quiet; Patricia Barber Cafe Blue one step). Beautiful sense of air and space.

On rock/jazz i.e. Electric Ladyland box set or Beck Blow By Blow 45 rpm plenty of slam and super wide soundstage.

I have not yet gone back to the Aria to do direct comparison but will as soon as mullard tube breaks in but I also have not had a reason or inclination  to do that as the highs and sound stage are definitely much improved.

The EQ-500 definitely sounds better after some warm up, at least 30 minutes. YMMV but through the 3.7 maggies and REL s510’s this is a winner for me.