What cartridge to use....Rega RB25 Structural Mod

Yes,Poaul Ladegaard in his paper on mechanical resonances in turntables established that lightweight arms are really the best performers overall.I think he used a Danish Moerch arm as one of the arms in the experiment actually.This was cognizant also on the best arm /cartridge match in terms of cartridge resonance and system matching.If you can find a good used UP-4 I would probably try it myself.I don't think Garth is misleading though and I am aware there are better arms out there.Take Mark Baker's development of the basic Rega into the Encounter arm for example.You can see what could be done to it.

I really think that all this discussion about arms needs to be related to the cartridge/cartridges that are to be used with these arms.

Not every tonearm is correct for every cartridge.
To discuss arms without cartridges in mind is quite "out of context" in my opinion.

Regarding the cartridge originally mentioned in the thread topic, I wouln't recommend the use of something like a Koetsu, DL103R, or Shelter in most unipivot arms(although there are a few exceptions), especially any light weight unipivot arms.

All unipivot arms are pushed to their limits of stability with low compliance cartridges, and even the actions of the tonearm designers themselves, such as Graham, and Weisfield, and others, have incorporated "outriggers" or other types of stabilizers to help their unipivot arms deal with the lower compliance cartridges.

Matching is critical, and proper matching goes beyond simple mass/resonance calcs.

“All unipivot arms are pushed to their limits of stability with low compliance cartridges”

Rubbish. That sweeping statement is simply not true. I have never ever had any stability issues with any properly set up unipivot in more than a decade that I have used unipvots.

“I wouln't recommend the use of something like a Koetsu, DL103R, or Shelter in most unipivot arms(although there are a few exceptions), especially any light weight unipivot arms.”

Since the carts you mention are low compliance carts, it would be rather dumb to use them on a lightweight arm, unipivot or not.

I have used all the carts you mention (Koetsu Rosewood, Shelter 501 and DL103) on a Morch UP4 (blue dot arm wand – 14 grams) and 12 inch Scheu Classic II (also 14 grams) with great results. I tried the same carts (on same table) on a modified R250 and it compared badly to the Morch and Scheu.

“Matching is critical, and proper matching goes beyond simple mass/resonance calcs.”

It goes way beyond that and includes the choice of turntable and the stand/isolation employed..

And again I feel the need to emphasize that I have no motive to prefer one arm over another other than for purposes of sound quality. I do not sell arms (or promote tweaks) for any audio equipment.

Regards
Paul

I am not suprised that you preferred the Moerch and Scheu over just a rewired RB 250 because you have to do more than just a rewire.The smearing is there very noticeably until you also add a metal stub and then use TWL's amazing Tracking Weight Tweak.The control in the RB 250 then becomes feather-touch.A form of VTA adjustment is also required and then all your attention must be given to adjusting the base-nut to EXACTLY the right tension(Usually Finger-Tight with just a Nip).This is critical and quite labourious at first but the Rega literally "sings" when it comes together.Anything from cartridges as different as the old Linn Asak(MC)(Supex 1000) to the Ortofon VMS 20E Mk11(M.Iron)for example,sound great.The smeared darkness and murkiness that people notice with a Rega disappears,it is an extremely sensitive and balanced arm in reality.I guess as I don't have the urge to change now,it's doing something o.k.

“I am not su[r]prised that you preferred the Moerch and Scheu over just a rewired RB 250 because you have to do more than just a rewire”

Sigh ...

I used a number of stubs different stubs – brass stub & weight (from Brit Audio) a Michell stub & weight and a custom-made brass counter weight. They did improve the sound (especially on the 250’s) but did not bring it even close to the sound of a top-flight arm. In fact I would say the structural mod seems to be a bigger improvement that the rewire itself

I also tried it with spacers, Easy Rizer VTA, Pete Riggle VTA on the fly and the VPI VTA adjuster. The best sounding to my ear was with using the VPI adjuster, but again it was very disappointing compared to Morch.

The modified RB250/300 was on par with the RB600 I tried. Your posting indicating the level of quality (or should I say lack there of) pertaining to the bearings, fall in with my observations.

“A form of VTA adjustment is also required and then all your attention must be given to adjusting the base-nut to EXACTLY the right tension(Usually Finger-Tight with just a Nip).This is critical and quite labourious at first but the Rega literally "sings" when it comes together”

If you are eluding the poor performance is due to bad setup you are sorely mistaken. And no, the Rega only sings when you are not used to anything better – and there are many better arms out there.

Don't get me wrong, I think and RB250 is good value for money. If you happen like it, that is cool. Hifi is about enjoying what you listen to, no?

Ultimately though, you get what you pay for. Running a Koetsu on a RB is casting pearls to the swine.

Regards
Paul