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RB300 tweaking problem

I have an RB300 mounted on a Townshend Rock Mk. III. This turntable incorporates a damping trough at the cartridge. To use this trough, a outrigger assembly is mounted at the headshell. The RB300 came from Townshend. It came with the tungsten CW w/ an additional weight epoxied to it to offset the added mass of the outrigger. The diameter of the hole on the additional weight is larger than the shaft. Its weight is being supported by the tungsten cw.

I am using the latest Shelter 501.

I thought I would try one of the cw upgrades. I went with the Mitchell. The problem that I am having is that in order to load the cartridge at 1.8 grams, the center of the main weight is a full 2" behind the pivot.

Any suggestions here? Should I add more mass to the Mitchell? If so, how?

Thanks for any help.
smctigue
12 responses Add your response
nghiep's avatar
nghiep
79 posts
 
Is there a noticeable sonic differences with the cartridge damping trought? Thanks
smctigue OP
9 posts
 
Thanks, maybe I'll have better luck calling Townshend.
tafka_steve
115 posts
 
I bought an extra vial of damping fluid from Townshend back in 2001. He should still have some, as he is still making turntables that use the damping trough (according to HFNRR). If you have no luck with him, I can probably supply you with some.

FYI, the Townshend has been in my second (bedroom) system for 4 years. I went nuts and bought a Walker Proscenium with a Dynavector XV-1 to replace it in my primary system. And yes, it was worth it.
smctigue OP
9 posts
 
Agreed. I felt the same way about the Mitchell.

Where are you getting your damping fluid? I've emailed Townshend a few times with no luck.
tafka_steve
115 posts
 
Honestly, I can barely detect the sonic difference (slightly cleaner transient/dynamic peaks with the Heavyweight). I think the front-end damping paddle/trough of Townshend's arms removes arm resonance colorations (certainly the tonearm/cartridge resonant peak is nullified) and this is why the difference is so minor.
smctigue OP
9 posts
 
Tafka, thanks, very interesting. Our cartridges weight the same. I also load mine at 1.8 grams. Are you happy with the Heavyweight? How has it improved over the Townshend supplied cw. Thanks.
tafka_steve
115 posts
 
>>The tracking force is set at 3.5. According to the Mitchell literature, doing so deactivates the spring.<<

Correct. The spring applies upward force in Rega arms, not a downward force. But deactivating the spring means that you have to move the counterweight further from the pivot. If you want to operate with the spring deactivated, you'll have to add more mass to the counterweight to move it closer to the pivot.

FWIW, I use a Expressimo Heavyweight on my Townshend-modified Rega and with the Lyra Helikon tracking at 1.8 g. I have the counterweight hanging off the end of the arm tube as far as it can go. If I used a heavier cartridge or more tracking force, I'd have to add mass to the Heavyweight.
smctigue OP
9 posts
 
The tracking force is set at 3.5. According to the Mitchell literature, doing so deactivates the spring.
smctigue OP
9 posts
 
It's the stock assembly. I am the original owner.
plato
1,543 posts
 
Hmmm, that's weird. I had a Rock Mk-3 with the Rega RB300 and as I recall the stock outrigger assembly was very light in weight. Has someone made a home-made outrigger that weighs a lot more, by any chance? If so, perhaps you could order or find the original assembly. And if not, I'm sure it wouldn't be that difficult to make one. Any machinist could do this easily... I never had a problem balancing the arm and I don't think I needed the extra weight.
tafka_steve
115 posts
 
You can move the weight closer to the pivot if you have an external tracking force gauge. Set the Rega spring gauge tracking force to zero, then move the counterweight to apply the tracking force measured on an external gauge. The disadvantage of this method is that the Rega spring is actually at its maximum tension to maximize upward force at the 0 gram setting, and this may color the sound.
brusson's avatar
brusson
9 posts
 
Don't use the spring to set tracking force; use the counterweight(s)and a separate tracking force gauge. That should move them closer to the pivot point.
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