Green bullet

Hi, Mark

Whoever told you that gave you good advice. Wish someone had told me that -I bought a 520DX when I was starting out and should have saved my money. 

Chronologically, it went like this, from mid-forties to today:  

1949–Model 520 introduced - “R5” element ( “Black Label CR”)

1954–switched to (“White label CR”)

1960 - switched to R7 single impedance CM with opaque epoxy (“Premium CM)”1963-  switched to single impedance CM with translucent epoxy (“Single impedance CM”)1980–Model 520D introduced. R44 element. (“Dual impedance CM”)1997–Model 520D discontinued.1997–Model 520DX introduced. Dual impedance, modern design mylar diaphragm 

With each successive generation, the elements get a little cleaner, gain a little more high frequency response, and a little more headroom (ability to withstand high sound pressure levels without distortion.) Of course since what we crave is the "right" kind of distortion, we often prefer the older elements. 

The 520DX is also bigger and heavier than any of its predecessors. The large size makes them very difficult to learn to cup effectively unless you have big hands, and the weight causes hand fatigue.

For a "more than you ever wanted to know" treatise on these elements see http://www.greenbulletmics.com/

The older the better! Of course the risk is higher that the original element won't work, but as a rule the Shure CR and CM elements are very reliable, even at their present age. If not - I can help you with that too.

Cheers

/Greg