Measuring Pickups 1967 Article... comments?

[Ldg]

It's been a year or more since I formed the view that cantilevers might well flex. At the time, I constructed a theoretical model of the cantilever as an underdamped transmission line. i.e. as the stylus moves, a transverse vibration propagates along the cantilever, rather than the whole cantilever moving as a body.

At the time I posted this plot, which is a calculation of mechanical impedance as seen by the stylus moving a cantilever of typical construction which is pivoted at one end. With zero damping, because maths was too hard to incorporate, so I sketched on the effect of damping as a dotted line :

Now, this could be rubbish. I didn't progress it because it seemed to imply that cantilever flex defined mechanical impedance, rather than the elastomer. Which seems implausible. But, if one believes cantilevers can flex enough to be self resonant, there should be an impedance dip at the quadrature frequency (resf/4).

Were this true, cantilever flex would be providing a significant part of cartridge suspension spring, i think. This is the sort of iconoclastic thing that is awkward to ignore if one accepts the top resonance is due to cantilever flex though.

But, I could well be wrong. Or I may be right, it does fit the profile. I think it needs an independant confirmation.

[davidsrsb]

If the cantilever is resonant, there is nothing fundamentally superior for MCs, the effect must be due to the detachable stylus design leading to lower resonance

[dlaloum]

I have actually measured additional distortion from a loose stylus mounting vibrating - the measured THD dropped markedly when the mounting was immobilised.

Immobilising the mounting does not require the stylus to be non-detachable.

Technics, Nagaoka and Audio Technica either have or had top cartridges with the cartridge mounting screwing into the body...

My testing of MC's also shows the exact same resonance... which does not explain what causes it.

The advantage of MC's is primarily (I believe) a result of much lower inductance/resistance... so the cantilever response is naked and not adjusted for by an Inductance/Capacitance EQ circuit. (there may also be some advantages to the more sophisticated MC magnetic circuits... not sure about that...)

The very best MM's seem to all have been at the low inductance end of the spectrum... in some cases (Pickering XLZ7500s) as low as many MC's (3mH)- in which case I question whether the MC principle has ANY advantage whatsoever...

The early (Pritchard) XLM's were under 300mH, V15V was 330mH, AT25 88mH, EPC100 80mH, etc...

[Ldg]

If one desires, even MM inductance/capacitance issues are avoidable in pretty much any MM/MI cartridge, see my thread on transimpedance MM/MI preamps. Interesting, and notable, that the Walton 1967 article is silent on the issue. Other than to touch on it by saying 'it is clear we need not compare frequency response curves for every decibel of variation like an exercise in "one-upmanship" '.....which seems to say all that's necessary, really. There are bigger fish to fry as to performance, implies the author. Which is what I've been posting for ages.

The matter of cantilever flex, or not, is the same issue for MM or MC, of course.

[missan]

High LD.
Am I understanding this correctly about vinyl resonance. The tip equivalent mass isn´t really interesting regarding resonance, but for needle acceleration.
Some needles have the same cantilever but differs in needle shape, like from OM5E to OM40. Different needle mass are stated, this should not really be possible to conclude using part one from the article?
missan

[Ldg]

High LD.
Am I understanding this correctly about vinyl resonance. The tip equivalent mass isn´t really interesting regarding resonance, but for needle acceleration.
Some needles have the same cantilever but differs in needle shape, like from OM5E to OM40. Different needle mass are stated, this should not really be possible to conclude using part one from the article?
missan

Hi missan. Yes, and I'm sure you already know these can be pretty tricky concepts. AFAIK, spec tip equivalent mass is worked backwards from VTF required to track hf tones. Calculated as though the cantilever is a rigid body. But, if the cantilever is not rigid, that model obviously becomes suspect.

There's no question OM cartridges improve in hf trackability through the range. Yet have similar cantilever, suspension and armature. Then true inertia difference from stylus tip variation seems very small in the classic sense. Nevertheless, working backwards from trackability could yield big false differences in spec tip equivalent mass. I'm not convinced 'tip mass' has a true inertia meaning when worked backwards from trackability.

I suspect improved hf trackability throughout the OM range is really due, in part, to diamond tip inertia having far more significance than a rigid cantilever model might suggest. Plus a big helping kick from lower friction due to improved tip polish and cut/profile, progressing in the OM range.

I'm not convinced 'effective tip mass' has much meaning if the cantilver can flex. The classic model assumes a rigid cantilever, and I'm not sure that's true. I think you once pointed out that nothing's really rigid in dynamics, IIRC, missan.