What are the physical differences between the rega rb250, rb300, rb600 and rb900?
Rega Rear end stub:
The most significant difference between the arms is that the RB300, RB600 & RB900 have a stainless steel stub at the rear end where the rega counterweight is mounted. The rear rega stub on the RB250 is plastic. This difference alone explains the RB250’s inferiority to the RB300 RB600 and RB900. Once modified this difference is removed and the modded RB250 is superior to the RB300, RB600 and RB900.
The counterweight on the Rega RB300 RB600 and RB900 is either tungsten or stainless steel. The rega counterweight on the Rega RB250 and RB251 is black in colour and made from steel..
Rega Tonearm Bearings:
The rega tonearm bearings in the RB300 and upper arms have a higher grade ABEC specification. The bearings are also graded for tighter dimensional tolerance as the arms increase in price.
Tracking force adjustment:
The Rega RB300 RB600 and RB900 have a spring dial system to set tracking force. On the Rega RB250 and RB251 tracking force is adjusted by rotating the counterweight. Once modified you will need a stylus balance to set the tracking weight on the RB250.
The spring mechanism is removed by some audiophiles as it is found to introduce resonance and the arms sound better without it. We do not recommend this course of action as it devalues the resale value of your Rega tonearm and the Rega spring cannot be replaced once it is removed.
Rega tonearm base:
The mounting body of the Rega RB300 is made of stainless steel, whereas the mounting body of the rega RB250 is made of brass. The arm base on the rb900 is very different and is held by 3 bolts which has a better decoupling effect than the standard arm.
The latest generation of arms all use the 3 point mounting system on the base. The lower arms use plastic to form the base but upper arms use metal. The change from threaded bases was not popular in many quarters as it makes adjusting the vta laborious. The old Rega threaded bases can be fitted with threaded vta adjusters which gives them infinite adjustment.
It is difficult to say what prompted Rega to change from the threaded base to the 3 point mounting. Some think it was a cost issue and moulded plastic is easier but it is also likely that there was a performance gain for some people. In our view the perceived performance increase was observed because most Rega tonearms with threaded bases are tightened hard onto the armboard. Tightness is surprisingly detrimental to performance and a totally misguided practice, based on intuition rather than proven comparison results.