Spiral Groove Centroid Arm

[MylesBAstor]

Know a couple of members have experience with Allen's arm. I've always respected his work but that oil bath and changing heights and tracking force has always intimidated me. Would love to know more about the Centroid arm!

[Guest]

Dennis Davis tells all at TAB: Spiral Groove • Centroid Tonearm; iirc, he bought the review unit.

[MylesBAstor]

Is that current?

That being the tonearm currently in his system? I believe so.

[jfrech]

I bought one about a year and a 1/2 ago. Very simple and easy to set up. First thing you notice about when when playing is how quiet it is...and then how the dynamics emerge from there. I've used a Lyra Atlas, Jan Allaerts MC2 Finish and a Goldfinger Statement v2 all with great sound.

-The tracking force is as easy as it gets...just turn a wheel...
-Oil bath? Not sure...what you mean here...might be a older model?
-Heights is easy to...just insert a Allen Wrench. It doesn't not have a micrometer or something to easily repeat changes. I do tend to go 1/8 turn up or down for 180 vs 200 grams. Your ears can guide you here.

I do like the ability to change arm cables. I know a lot of folks like one cable from the cartridge clips to the phono stage. But I've found 1 (more) break seems to be trumped by a better cable.

It's the best arm I've owned for sound quality (vs prior arms like SME IV.Vi, Triplanar, Schroeder LT)

[Rob]

Know a couple of members have experience with Allen's arm. I've always respected his work but that oil bath and changing heights and tracking force has always intimidated me. Would love to know more about the Centroid arm!

I've been using the RPM-2 which pre-dates the Centroid (both uni-pivots), it was Fremer's reference on the Simon Yorke 'table before he acquired the Caliburn/Cobra table/arm. the major change on the Centroid was the counter balanced weight right on the pivot giving the 'arm the lowest moment of inertia possible. Allen was granted a patent for this. the pivot point on both arms is on the same horizontal plane as the LP surface (which doesn't change with VTA like most arms) and is immune to warp wow, AFAIK the RPM-2 was the first American arm with this design. The RPM-2 immerses the bottom of the bearing cup in an oil bath as an integral part of its design, the Centroid doesn't. damping is adjusted by adding or subtracting oil (Mobil 1, 5W) easy enough using a syringe. tracking force uses a thumb wheel like the Centroid.

The coup de gras is the set-up jig (also patented) which is the same jig for both arms. The hole locates the spindle to pivot distance and the vertical rods locate the arm wand, tangency is insured and the stylus target and reference lines on the mirror provide the correct overhang and zenith. I can install a cart, balance it and get it close to ideal in 10 mins. About as quick as Bob's jig for the Phantom.

[mep]

What is that gooey looking mung on the back of the bearing housing Rob?

[Rob]

sharp eye! Its a rubbery substance used to decouple the counter balance beam from the body the tonearm . the beam will wobble slightly when applying force to it. If you recall your ET-2 was decoupled in a similar way, Ed Thigpen used a flat spring at the end of the bearing tube where the counter weight beam attaches.

[MylesBAstor]

I've been using the RPM-2 which pre-dates the Centroid (both uni-pivots), it was Fremer's reference on the Simon Yorke 'table before he acquired the Caliburn/Cobra table/arm. the major change on the Centroid was the counter balanced weight right on the pivot giving the 'arm the lowest moment of inertia possible. Allen was granted a patent for this. the pivot point on both arms is on the same horizontal plane as the LP surface (which doesn't change with VTA like most arms) and is immune to warp wow, AFAIK the RPM-2 was the first American arm with this design. The RPM-2 immerses the bottom of the bearing cup in an oil bath as an integral part of its design, the Centroid doesn't. damping is adjusted by adding or subtracting oil (Mobil 1, 5W) easy enough using a syringe. tracking force uses a thumb wheel like the Centroid.

The coup de gras is the set-up jig (also patented) which is the same jig for both arms. The hole locates the spindle to pivot distance and the vertical rods locate the arm wand, tangency is insured and the stylus target and reference lines on the mirror provide the correct overhang and zenith. I can install a cart, balance it and get it close to ideal in 10 mins. About as quick as Bob's jig for the Phantom.

Thanks for the detailed info Rob. I must have been thinking about the original arm.