In article , Keith G
wrote:

"Don Pearce" wrote in message
...


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.


How does the HF damping thing work? It seems to me that if you can
dissipate energy quickly enough for critical damping at HF, it will be
almost solid at the main LF resonance


The energy is dissipated in the tonearm, not the cartridge.

Sorry, Keith, but you are confusing two quite different resonance
mechanisms. The HF one does not involve the arm. It is the resonance
between the effective cantilever inertia (not the arm) against the
suspension return force inside the catridge. So you can measure this and
observe it even when the cartridge isn't in an arm or touching and LP.

Whereas the LF resonance is between the suspension compliance and the
effective mass of the cartridge and arm. Quite different.

To make life more interesting, the effective return force versus
displacement at HF is quite likely to have a totally different compliance
value than the one exhibited at LF.


See:

"A decade ago, high-compliance cartridges were the rage and these needed
to mate with very low mass tonearms. However, today's heavier,
lower-compliance phono cartridges (especially moving coils) have
required tonearm designers/manufacturers to reorient themselves in the
direction of medium to high-mass arms.

To deal with the LF arm-cart resonance, not the HF one. The aim being to
put the LF resonant frequency at a relatively harmless frequency, between
warps and music, and to damp the peaking at that frequency.


Further, some of the currently available MC cartridges put back a
tremendous amount of energy into the arm. This reflected energy takes
the form of standing waves, which travel up and down the length of the
tonearm, potentially creating mis-tracking problems and/or frequency
dependent cancellation. A well designed tonearm will dissipate this
energy, rather than reflecting it back to the cartridge. The ability of
the arm to accomplish this will be dependent upon bearing design,
internal damping and rigidity."

Yes, and has little or nothing to do with either of the other two
resonances I am talking about. :-) You are correct. Low compliance MC
designs can give more problems with vibrations into the arm. But that is
another story to the two resonances we have been discussing.

From he

http://www.gcaudio.com/resources/how...cartridge.html

Then stop worrying about it....

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.

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.

These things were all investigated some decades ago, and reported in the
magazines and journals. People like Kogan of Shure knew well about them, as
I am sure (pun) so did others at Empire, Ortofon, etc.

But I am less confident about some modern carts which we are told were
designed 'by ear'. The best the user can do is hope to mitigate this by
playing with electronic loading. Or by using a differerent cartridge.

Maybe I should move up my 'to do list' writing about this.It seems to be
another aspect of LP engineering that has largely been forgotten since the
main engineering was done some decades ago.

Slainte,

Jim

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