Tuesday, February 8, 2011

Rega RB250 revisited

For the past week or so I have been experimenting with the Rega RB250 tonearm with the aim of trying to confirm if all the vinyl experts out there, especially the Origin Live folks, were correct when they said the RB250 when modded can outperform the top-end Rega tonearms.

The RB250 has vertical bearings on both sides of the armtube which makes it inherently more stable compared with the RB300 (and its variants) which has the vertical bearing only on one side while the other side houses the coil spring to control the VTF.

My Rega RB250 tonearm is not from an old turntable; it is a newly-made model from a special edition issue for Malaysian vinyl addicts (read: http://hi-fi-avenue.blogspot.com/2010/11/limited-editions-of-rega-rb250-rb300.html)

Since I was on leave for Chinese New Year, I had some time to spare and I took my old Rega Planar 3 to the 'workshop'. First I removed the RB300 tonearm, which was surprisingly quite an easy job.

Then I took the RB250 tonearm and inserted the cables and then the steel base through the hole in the plinth. There was some play and I thought the base of the RB300 was bigger, but when I checked with the RB300, I found out that there was some play with it too.

So, I screwed the RB250 with the supplied thin nut. With my finger and thumb I turned the nut as tightly as I could and then with an adjustable spanner, I screwed it tighter with just a little turn.

Getting the tonearm to be parallel to the edge of the turntable is actually quite difficult as it tends to shift its position when the screw is tightened. After some struggling I managed to get it more or less parallel to the plinth's edge.

The limited edition Rega RB250 tonearm.

The RB250 about to be fitted into the hole in the plinth.
Note the plastic end-stub

The old Rega Planar 3 with RB250 tonearm.

The RB250's plastic end-stub and counterweight.

The RB250 in action.

Michael Lim's steel end-stub and underslung
counterweight fitted on the RB250.
After that it was a matter of removing the Rega Exact cartridge from the RB300 and fitting it to the RB250. I used the third screw so that the cartridge would be set up according to Rega's alignment which is the easier solution. It may sound simple, but the entire operation took me one and a half hours to complete.

After screwing in the plastic end-stub and the counterweight, it was a matter of using the Clearaudio digital stylus gauge to set the VTF to around 1.8gms. Setting the anti-skating force is quite tricky as even at the '0' mark the tonearm swings back. Thus '0' is not exactly '0' with Rega's magnetic anti-skating system.

Then I chanced on a pretty reliable way to set the anti-skating force. I simply placed the stylus on the glass platter. Since the glass has a smooth surface, you can see the tonearm skating outwards when the anti-skating force is set too high.

I reduced the anti-skating force till the stylus did not skate when it was placed somewhere between the spindle and the edge of the glass platter. The cartridge seemed to track quite well when I played an album and the sound seemed quite balanced between the left and right channels.

After playing a few albums, I can confirm that the audiophiles who said the weakest part of the RB250 is the plastic end stub - which by the way is hollow - are correct.

The stock RB250 sounds more transparent and clearer than the stock RB300, but it also sounds rather lean.

I replaced the plastic end-stub and counterweight with Michael Lim’s steel end-stub and underslung counterweight. There was a dramatic difference - the low bass went deeper with more definition and the mid and upper-bass filled up to give the music lots more body and richness while retaining the RB250’s inherent transparency.

I have also been using lead-vinyl mats and a carbon fibre donut mat from sLam Audio with Rega’s glass platter and the combination creates music with a neutral balance and great clarity with deep and solid but tuneful bass. The listening sessions were carried out with the turntable on my gel isolation platform (read: http://hi-fi-avenue.blogspot.com/2011/01/new-years-tweak-gel-isolation-platform.html).

I have not tested my modded RB250 against the RB700 or RB1000, but I can safely state that the modded RB300 - even with the spring disengaged - does not outperform the modded RB250. Yes, the Origin Live chaps are correct - a modded RB250 can really sing and I am not sure why the Rega folks did not bother to improve the design.

1 comment:

  1. Nice post. I have done similar, and agree with your results. RB250 is better. I only got an RB300 to really "sing" by loading it with a heavier cartridge and using an underslung metal counterweight (despite its existing counterweight already being made of tungsten). However, I think the same mods with an RB250 would have at least equalled the result.