Wednesday, January 12, 2011

Tweaking the Rega RB300/301 tonearm

Rega tonearms come in two forms - one has vertical tracking force utilising gravity and the other uses a coil spring (for a negative downforce, actually).

In the former group are those based on the RB250/251 while the other group comprises variants of the RB300/301.


Much has been said in various online forums about the coil spring adding resonances to the tonearm and causing the sound to be thick and smeared.


The right tweak, according to this website http://www.tonearm.co.uk/rega-arms-hi-fi-world.htm is to disable the spring by turning the dial to past the ‘3’ mark and move the counterweight forward or backward on the end stub and measure the tracking force with a stylus gauge.


Another website - http://www.tnt-audio.com/sorgenti/analogue_bits_e.html - recommends placing pieces of felt between the coils of the spring after disabling it.



The coil spring.

Turn the VTF dial past the '3' mark to disengage the coil spring.

There are some audiophiles who have actually removed the coil spring altogether.


Since I am now the proud owner of a Clearaudio digital stylus gauge, I can easily check out the tweak to see if it works.


The RB300 of my Rega Planar 3 has Michael Lim’s end-stub and underslung counterweight and it was a matter of setting the vertical tracking force dial to ‘0’ and adjusting the counterweight so that the tonearm was floating slightly above the mat.


Then I turned the dial to around 1.5 and used the Clearaudio stylus gauge to check the tracking force. I can confirm that the dial is not accurate and a good stylus gauge is a must if you want to venture into the world of vinyl. I set tracking force of the Rega Exact mm cartridge at 1.85 gms and the anti-skating at around 1.6.


I spun two test albums that I have been listening to for the past few weeks - Miles Davis’ The Man With The Horn and Bob Dylan’s Together Through Life 180gm double LP.


With the coil spring engaged, the soundstage became narrower and somewhat congested - there was less separation of the voices and instruments, and there was less depth.


Leading edges of music were ‘rounded off’ and the highs were smooth and some instruments like the trumpet, electric guitar and cymbals lacked some ‘bite ‘and shimmer.


Then I reversed the process - I set the VTF dial to past ‘3’ to disengage the spring and adjusted the counterweight to get the 1.85 gms tracing force.

However, the counterweight was a bit further back which increased the effective mass of the tonearm, but there should be no problems with a low-compliance cartridge.


Listening to the same LPs again, I could discern that with the spring disengaged, the soundstage widened and was deeper, there was more space between vocals and instruments, the leading edges became sharper and dynamics improved. The treble had the right bite and shimmer.


All the other audiophiles who did this tweak years ago are correct - with the spring disengaged, the RB300/301 can sing like a bird in spring.



1 comment:

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