Sorry, something went wrong in the transfer. C2 should in fact be a 1K resistor and not at all a capacitor.
And FR is within 1dB up to 400Khz and not within 0.1 dB.
Hans
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The algorithm is still R1=2*Lcart-Rcart. So a 580mH + 460Ohm Cart gives 1160-460=700Ohm.
In the balanced setup this 700 Ohm is divided in two equal parts, one at each input, to achieve an optimal CMRR.
Hans
Quite simple, a new pole higher than the current 150 Hz will have to be used and all values around the first stage will have to be recalculated.
When you have a real example, I can show how this will look.
Hans
Don't spend the time, I was just going from memory that the Grado's would all come out that way. Not sure of the benefits of all this with MI carts anyway.
For some bizarre reason, the vast majority of MM/MI carts seem to end up with R1 small and positive..........all good.
As for Grado's MI arrangement, which is in principle an exception, it doesn't stand to benefit if inductance in play is as low as it typically measures externally as a 2 wire port. However, a few years back there were a few loose ends IIRC as to effect on generator f response of external loading that perhaps suggested more to what might be going on than meets the eye ? Think transimpedance loading might settle the matter once and for all, but personally would suggest it's one to lay down for a rainy day........
LD
Yes, the current spec on the motor assembly for most of them is 45mH and 475 Ohms. Seems a high ratio (fewer turns of crazy small wire???) or do modern high N magnets somehow enable this, I'm out of my element here.
This element would have it's -3dB point at 1680Hz without a resistor inserted in series.
With a modified Aurak, this -3dB point would have to be shifted from 1680Hz to 2123Hz (=75usec).
This is still easy to achieve with C4=0.6n and R13=115K.
Hans
AFAIK the arrangement is still 2 fairly conventional coils in series, as often found in MM/MI, but having opposite sense in this case, so mutual inductance cancels most self inductance and only leakage inductance remains. Hence the fairly conventional R and conventional looking coils.
It's curious to then to reconcile the low 2-wire port inductance with past reported observations of effects of loading variation, and measurements of audioband f response on Paul Miller's website, I think. There was some discussion a few years back as to how mutual inductance appears to the generator. But, with a few caveats, I think it's best to treat those carts at face value as to 2-wire port inductance.
Aside, inductance doesn't depend on permanent or static field strength, Scott. Rather, on the permeability of the coil core material and its geometry.
LD
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Standing in corner again, copper is not superconductor either.
Though I did mean getting more output with fewer turns, but in retrospect the logic of using ultra thin wire to get the R back up to 450 Ohms makes no sense.
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I don't think that's how it's done in this case. AFAIK, the coils are wired in series antiphase, but effectively on a common magnetic core, yet the direction of generator induced flux changes is also opposite in each coil due to a cunning generator arrangement that divides flux between them in sort of push-pull arrangement depending on position of an armature. AFAIK. IIRC there's a patent that describes it.
LD
US 3683128, 3694586, 3881073, 4031336 (reading first and second is enough)
FLUX-BRIDGING STEREOPHONIC PICKUP
TOROIDAL ARMATURE STEREOPHONIC PICKUP
George
That is in general my finding with using a normal MM input (47k) the inductance and inevitable cable capacitance resonance with the inductance does not add as much noise. Using JFET's one can approach the noise limit of solely the series R. In any case, 80dB would leave you with surface noise only I suspect.
Yes, IME Riaa preamp noise above ca. 65dBA can't be heard at normal playing levels with the PU Arm in the air.
So 80dBA is way above the surface noise and offers a very comfortable margin.
Hans
