"Jim Lesurf" wrote in message
...
In article , Trevor Wilson
wrote:

"Don Pearce" wrote in message
...


The damping should all be associated with the spring - which is the
stylus cantilever suspension. There should be no expectation of extra
damping associated with the arm bearing, which is ideally as free to
move as possible. Indeed damping of the arm bearing impedes arm
movement that is needed to prevent low frequency high-amplitude stylus
excursions.

In other words, what is being damped is the spring - mass system of
the cantilever and effective arm mass. The right thing to damp is the
spring involved in that resonant system. Ie, the damping must be in
the cartridge.

**Unfortunately when theory meets reality, things don't always go to
plan. In my long experience (30+ years) running dozens of different MC
and MM carts with dozens of arms (including most SME models), I have
found that arm damping is critical to decent performance with MC carts.
SME arms (knife edge bearing types) are amongst the worst choices for
MC carts. This arm is one of the best choices, IME:

http://www.dynavector.com/products/t.../e_507mk2.html

Even more unfortunately, a lack of damping in the stylus cantilever may
tend to produce a marked HF resonance. Damping of the arm won't fix that
as
the arm isn't really involved.

**No argument from me. I refer you, again, to the Dynavector 17d (I,II,III)
cartridge. Their unique suspension system managed to push any resonance
issues well beyond 50kHz and out of harm's way. The arm design is to deal
with LF energy generated by most MC carts.


One of the points that people nowdays seem to overlook is the work Shure
and others put into having optimal cantilever damping for HF reasons.
People seem aware of the high compliance and, to a lesser extent, low tip
mass, but damping rarely seems to be considered.

**The art and science of arm/cartridge matching is a rapidly dissapearing
one. Even Shure have discontinued one of the finest cartridges ever
designed - the V15-V. Sad.


The presumption seems to be that when you see an HF resonance with a MM it
must be purely 'electronic' in nature. This isn't really the case. When
experimenting with electronic loading you may simply be trying to trade
off
two quite different HF LP resonances - one electronic and the other
mechanical - to get an overall optimum. But so far as I know, this has
largely been ignored in recent decades. Preumably because of the
(incorrect) assumption that MC designs are immune.

**On the contrary. Due to the low inductance of most MC designs, cantilever
choice becomes very important WRT HF response.


--
Trevor Wilson
www.rageaudio.com.au