Why is the price of new tonearms so high

I've kept out of this thread but now that we are getting contributions from people who actually understand tonearm design I thought I might contribute a little.

Frank it is true that VTF will increase with record thickness but by my calculations the effect is very small indeed. Taking a dynamically balanced arm and assuming the VTF adjustment allows say 30mN range for a full 360 degree rotation gives us an effective compliance around 47,000 um/mN assuming 225 mm arm length. A typical record thickness differential of 1mm will cause a change of about 0.02mN which is around 0.1% of typical tracking force.


Mark Kelly

Dear Quiddity, absolutely right. Furthermore - as T_bone has already noted, a long (spiral) spring of say 4-5 inch length will hardly alter its tension because of an increase of 1/1000 or less of its length.
Furthermore - while everybody is talking about small alternations due to record thickness, no one seems today to care about a VTA compliant to the cutting-angle of the groove of the record on the platter......

As for the dynamically balanced vs static balanced mode of tonearms, I would like to note, that every dynamically balanced tonearm is static balanced too.......

If I were Berlinta, I wouldn't use nor design a dynamically balanced tonearm too. This is hardly possible to incorporate into tonearms not featuring a fixed two-point bearing (i.e. gimbal or gimbal/knife). Hard to do at all with string, magnet or uni-pivot bearings.

Anyway - we will at least see one new dynamically balanced tonearm on the "market" within the next 12 months.

I am sure we'll have another very interesting thread then.

Most likely we'll see that tonearm at the RMAF in 2010 too.

Dear T_bone, how to dampen a spring to be used in a dynamically balanced tonearm has been nicely demonstrated by Isamu Ikeda in his (...here we go again...) FR-60 series.
A new or in stock condition FR-60 tonearm will feature a long spiral spring which is embedded in a lot of white and creamy grease.
Much more than you can see on any of the pictures of dismantled FR-64/66 on the web.

If a spring is fairly large, fairly wide in diameter and quite solid (stainless-steel) it is - due to its location at the very center of gravity and inertia and to its position in conjunction with the surrounding grease and the fact that its edge is in contact with another surface on the whole length - most unlikely to resonate at all.
There are many more light-weight parts much less dampened in many more high-ticket tonearms past and present who are much more likely to resonate and add colorations to the sonic picture than a hefty and highly damped by several different measures spring.
Furthermore we do see dynamically balanced - i.e. spring loaded VTF - in very different tonearms ranging from high effective mass (FR, Exculsive, MAX (depending on armwand and headshell)) to medium and low like MA-505, SME V et al.
So it is neitehr a measure taken to deal with warp or high compliance (most unlikely to go with a high effective mass tonearm anyway...).
Interesting enough we see dynamically balanced design in the most expensive stock toonearms of the early 1980ies:
The Exclusive EA-10, Micro Seiki MAX-282, FR-66s/fx and SME V - all dynamically balanced.
All made by fairly large companies and/or specialized tonearm-manufactures which tried to set the benchmark for the component.

Constant VTF independed from the static balance mode of the tonearm does have several virtues and no disadvantage.
It can however - not be incorporated in every tonearm. It depends on the bearing you choose.
Consequently there must be disagreement about the dynamically vs static balanced mode - depending what "school's" scholar you are.....

D (and others),
I can envisage the practical difficulties of applying dynamic balancing force onto a unipivot bearing. I can see similar problems if a magnetic bearing is not otherwise stabilized. However, if the thread/magnetic/hydraulic/whatever bearing has more than one support point, doesn't give the same stability as, at a minimum, a double knife-edge?

Next a look at the effect of "warp riding". Assume a standard "taco warp" so the warp frequency is 7 rad.s^-1. This gives a maximal velocity of .007 m.s^-1 in the vertical plane for each mm of vertical warp and a maximal acceleration of .049 m.s^-2 (again for each mm of vertical warp).

The product of this acceleration and the effective inertial mass of the arm / cart combination gives a maximal VTF variation when riding the warp. If the inertial mass were 25 g (say 15g arm plus 10g cartridge) and the warp were 5mm high, the maximal variation would be around 6.2 mN. A similar calculation allows a maximal warp tolerance to be derived for any arm / cart combination as a function of VTF.

The important point is that it has nothing to do with the balance of the arm but is stictly related to the moment of inertia (and the mass of the cart).

Mark Kelly