In article , Keith G
wrote:

"Jim Lesurf" wrote


Anyway, rightly or wrongly (and never having had a *low mass* tonearm to
worry about), I have always been under the impression that the
(medium-high mass) tonearm will usually take care of unwanted
'resonances' and that the headshell (with or without a blob of Blu Tack
and a handful of pound coins) will take care of any (HF?) misbehaviour
from within the cartridge itself??

No, I'm afraid that isn't so simple, either! :-)

At *low* frequencies then, yes, you can treat the arm as just being a
'mass' the back-forces from the stylus are trying to wiggle. But once you
go to high frequencies (say above a few hundred Hz) then the forces produce
effects better understood as sound vibrations. Having a 'heavy' arm may
reduce the amplitude of the vibrations. But the *energy* of the vibrations
involves how much mass is moving as well as the amplitude. And you then
have to assess how efficiently this energy is coupled from cartridge to arm
mountings, etc.


Nor is rigidity a perfect solution. Although arms do tend to be sold on
that basis at times. And materials like Blu Tack may not be as lossy as
people think. Seeing that they squidge and flow at LF doesn't ensure they
are very lossy at HF. Think potty putty. You can squidge it and over long
times it flows like treacle. But it also bounces.

Esoteric extremes aside, the reality is that most current carts seem to
run just fine on most current tonearms - according to recent posts, you
have a V15 on a (presumably) Technic S-shaped tonearm, Don runs an AT09
on an SME3009 and I have a V15/III on a simple Lenco (tube and cube)
tonearm as well as an AT05 (I believe it is) on another Technics
tonearm - all running quite happily, I surmise?

I also happily use my V15/III on a Technics arm that is nominally too heavy
for it. The 'price' is that it might be unhappy with LF ripples or warps as
the high effective mass shoves down the frequency of the LF resonance
compared to what I'd get with a 3009, say. Probably also peaks the
resonance, which again might cause problems with ripple on discs. Which as
I think someone said a while ago can also cause some preamp overload
problems if the preamp can't cope.


Yes, I do have the impression that some MC designers may well have
'stopped worrying about it'. :-) Alas, that may then cause their
designs to have resonances at HF which they haven't 'worried about' -
or maybe noticed.


Maybe they are operating (as I do) under the banner 'if you can't really
hear it, it don't really matter'...??


The problem is when the designer decides that what *they* can't hear *I*
won't notice either. They could be wrong. Particularly in a world where
they can't dictate what arm and preamp and LPs you choose. Hence the value
of the designer doing measurements and having a clue about the engineering.
Lets them assess how likely it is that a percentage of customers will find
their design is crap for their use.


As Phil has said, these can occur in the 10's of kHz region. A problem
with MC designs is that the coils may contribute quite a large
effective intertia so far as the HF resonance is concerned.


'10's of kHz' definitely qualify as above - is there any 'side effect'
that I should know about?

Higher distortion. Clicks more noticable. Mistracking. Increased wear.

Slainte,

Jim

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