Shelter and Triplanar matching ?

Tenmus,

There is no serious mismatch between your cartridge and arm. The TriPlanar's nominal effective mass is 11g (varying slightly depending on which counterweights are used). A 901 with mounting hardware weighs approximately 10g and it has a compliance spec of 9 cu. To find their theoretical resonance frequency R we solve for the following formula:

R = 159/(SQRT((M+m)xC)) where:

M = effective mass of arm
m = mass of cartridge and hardware
C = compliance of cartridge

R = 159/SQRT((11+10)x9)
R = 11.57 Hz

This theoretical prediction was empirically confirmed on my TriPlanar VII/Shelter 901 combination. On the HFN&RR test record's resonance tracks I observed resonance frequencies of 11 Hz, + or -1. Not perfect but certainly acceptable.

You'll get slightly better bass and dynamics from your 901 by making the arm's effective mass as high as possible. To do this, use the bevelled weight (pushed all the way forward) plus the LIGHTEST donut-shaped weight that will balance the cartridge and give you the desired VTF. Using a LIGHTER c/w farther from the pivot INCREASES effective mass. IME the benefit will be slight but audible.

That said, I don't know why you're seeing visible shaking of the arm on non-warped records. I certainly never observed that in the year or more that I used my 901. Dogpile's suggestion to check the VTA tower set screw was a good one.

His suggestion to try a ZYX was also one I agree with, when you can. The TriPlanar is worthy of far better cartridges than a Shelter 901. A TriPlanar/UNIverse combination has proven synergistic and immensely pleasing for many people, including myself. Any ZYX from the Airy 2 upward will easily outplay a 901 on this arm.

Good luck,
Doug

HI Dogpile and Doug

First of all thank you VERY MUCH for your suggestions and PRECIOUS help.

Doug.

I cannot try right now what you advise to me because I had to send the TP back yesterday evening : the fine adjustment of azimut has been damaged by ANOTHER person (although it is a NEW ARM ????? )

I think It didn't have any influence on the problem that I descibed to you yesterday as the adjustment seemed to be visually perfect (the head shell was exactly in a horizontal positon )

VTA was perfectly tight (adjusted in a horizontal position) with the tower nearly in its highest position, as the armboard on my new Verdier is very low compared with the platter position.


I had the same problem ( in lower proportions) with the same cartridge and my Rega RB 900 wich was my previous tonearm before using the TP wich I received only last saturday. So I was also thinking it could be also a problem with this cartridge itself ( breaking in or anything else ...)

So I'll follow your advices when the TP is back wich I hope the sooner as possible (???) and I 'll give you news at this moment . I am afraid it's not tomorrow morning !!!

Thanks again

André

Heed Doug's comments and advice, he knows what he's talking about, always worked for me! Doug's suggestion about adding a second weight will definitely help.

Doug - regarding the above (R) formula, which spec value (C) should one use for the cartridge compliance? The 'vertical' value OR 'lateral' (horizontal) value? I assume the horizontal compliance is "less critical?"

Dogpile,

The formula works in both planes of course. If your cartridge has different V and H compliance, like a ZYX, run the formula twice.

The usual reason to check system resonance frequencies, whether by math or by test record, is simply to expose gross mis-matches - though frankly those are rare these days. Resonance frequencies won't tell you how a cartridge and arm will synergize and make music. Only listening will reveal that.

You do raise an interesting question though. I wouldn't assume either direction is less (or more) critical, but they are different. It might be theoretically desirable to have a higher R on the vertical axis and a lower R on the horizontal one.

Warps and floor-borne vibrations are largely vertical and fall mostly below 6Hz, so a slightly higher vertical R would help us avoid those. Some musical frequencies go as low as 16Hz and they are somewhat more horizontal, so we want horizontal R high enough to avoid them. I suppose a vertical R of 12-14Hz and a horizontal R of 8-10 Hz might be "ideal".

This would require either that the cartridge have a very non-linear suspension or that the arm have much higher effective mass on the horizontal axis than on the vertical. There are a few arms like that: air-bearing tangential arms and a few pivoted arms like the Dynavector 505/507 or a Twl-modded OL or Rega. Thanks to its relatively high horizontal inertia, my Twl-modded OL Silver was the most dynamic arm I've heard. Leading edge transient speed and extension were better than a TriPlanar, a Schroeder Reference or a Graham 2.2. I'm still impressed by Twl's brilliantly simple invention.

Tenmus,

I wonder how the azimuth adjustment (or anything else) was damaged on a new arm? I assume repairs will be covered by warranty.

Having to use the VTA tower near the top of its range "might" make it less stable and (let's face reality) the fit of the TriPlanar's VTA mechanism is not its best feature! Any chance of getting a taller armboard?

Since you had the same problem with this cartridge on another arm it does seem likely that the problem is in the cartridge. Shelter's QC is not as good as some, although I've never heard of this particular problem. Many 901's have misaligned cantilevers and/or non-square motors. Mine suffers from both problems (lucky me!) which makes it impossible to achieve decent channel seperation regardless of alignment or azimuth adjustment.