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The issue is really with cartridge behaviour...First the is the reactivity between inductance and capacitance leading to an electrical resonance.Then there is the cantilever which also has a mechanical resonance.So far every cartridge I have measured shows signs of the designers using the M-Resonance (mechanical) to balance out the F/R droop generated by inductance/capacitance, and sometimes the use of the E-Resonance (electrical resonance) to fill out and flatten the curve as well.So taken individually we most likely have phase issues at a minimum of 2 resonance points, plus there may also be some form of phase error as the electrical F/R drops off due to high capacitance/inductance. (not sure of that last one....)If the cantilever resonance (M-resonance) is beyond the audible range (say 25kHz +) and the e-resonance is also pushed way out through the use of either or both of low inductance and low capacitance - then there would be little or no phase error.So far I have measured all the following cartridges / styli and all have had signs of M-Resonances within the audio band....Shure 1000e with M97xE-SAS AT440MLaADC SuperXLMADC Digital Series IIOrtofon OM20Ortofon/Digitrack 300SEAs a result, achieving a flat F/R with all of these requires balancing an electrical HF droop with a mechanical peak.... as a minimum, and depending on the plot, sometimes using a slight E-Resonant peak to fill in a mid-high droop.I hope I am making sense.... if not I may need to post some actual plots...
Not quite...It appears, that resonances (whether mechanical or electrical) cause substantial phase anomalies...So wherever the setup is such that the base modelled (pure electrical) response has no "peak" - phase response will nicely follow amplitude response....BUT: if an electrical resonance (the peaks shown in the model plots) is present and used to balance out the frequency response, then although the amplitude frequency response is (relatively) flat, the phase response won't be...On the 300SE plot, all the R values above 45K have a resonant peak.... so there would be phase anomalies at all the higher resistances in a 149pf capacitance setup.Now this is all based on theory - I still have no way of measuring phase.for situations where the mechanical resonance rise begins above 15kHz and the peak itself is above 20kHz, I think phase will most likely be a non issue in terms of audibility. (at least in situations/setups where there is no electrical resonance)This would be a lot easier if phase measurement tools were as readily available as level measurement tools.David
The AT12 series in the early days were low inductance - later they moved to higher inductance - but right through both stages they were called AT12Sa... same colour, same look body - only way to tell is to get one and measure it! (AT13/14/15/20's also had early series with low inductance and later with high) David
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