Can a Nagaoka MP500 be converted to an MP700?

I would not buy either and use that money to buy a better overall cart. For the cost of a MP700 you can get into some nice MC carts. I have an MP500 and was never overly impressed with it, not as good as the similarly priced Hana SL or ML, Ortofon black, Sumiko songbird, AT various, etc. Granted you have an MC phono stage.

In Tokyo there are so many options that are better than the Nagaoka carts, I would recommend looking around a little more. You may find one of Audio Technica’s for a deal. Of course, this is my opinion, and others may have other suggestions.  

Lew, congrats. Great position to be in.

IMHO, the Nagaokas are great, cost of long term ownership is low as the stylii generally cost well less than half the price of the whole cartridge. If going Nag, I would bite the bullet for a new 700.

Another point, these are quite higher compliance than most MCs so one may work with a given tonearm, and one may not.

If in Japan, the Phasemation PP-200 is a honey of a MC cartridge at a very reasonable price.

Good luck, Lew.

Whereas you have always liked the mp500, my advice is to buy an mp700 while you are in Japan.  From my research it is a worthwhile improvement.

I have a MP700. Not fully run in yet. Fast, open, tight, neutral, with a fine top end. Tracking is excellent at 1.4g in a 12" Jelco TK850L with a heavy headshell.

It easily beats out an Audio Technica VM750SH which has a less sophisticated brighter but brash top end and smaller presence. 700 is bigger sounding. 

Interesting how a lot of folk on this forum are able to make a definitive statements on something they’ve never heard. I guess when you are spending someone else’s money, it’s easy to throw out anything that comes into your head.

The 700 is radically different from the 500, much better top end, no droop.