Right I wish Doug had mentioned it to me. A matched pair like the LSK489 makes a nice "0" offset source follower (one as a current source) and using that floating battery trick you've got a buffer with only output and ground connections to the board.
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That's nice. I suspect the ~700 dollar copies on the web will be of interest to but a fewAlthough I vastly prefer having a physical book.
I like physical books too, along with with original pressings of LPs. But once in a while the CD re-issue gets you most of the way there for a lot less!
I tore open a Grado with a broken cantilever the other day to expose the motor assembly, makes those claims look even sillier.
And yet the claims persist. I'm trying to imagine a suitable experiment to measure the magnitude of the effects.
When this topic came up I was tempted to quip that I joined the discussion with a great deal of variable reluctance
And yet the claims persist. I'm trying to imagine a suitable experiment to measure the magnitude of the effects.
When this topic came up I was tempted to quip that I joined the discussion with a great deal of variable reluctance
Gee a transducer works both ways. Apply 5 mV at 1000 hertz and look at motion. Probably under a microscope with a calibrated scale to see the rms motion. Compare that to a groove's reference modulation. The efficiency should apparent.
Having used an impedance meter to measure a cartridge and having not observed any motion I suspect you will need a very high power microscope.
For those who have never measured the impedance of a microphone or loudspeaker even blindfolded the difference between that and measuring resistance is obvious.
But as a curmudgeon in good standing I keep around a piece of glass used for making LCDs and a piece of clear anodized aluminum. For rookies I then measure the impedance of the glass surface which is quite low and then the aluminum which does not conduct. The resulting rookies' take on what they witnessed is interesting. If they ask I then used an ohmmeter just off the coated edge of the glass and on the unfinished part of the aluminum. This results in the expected results. Then I demonstrate the real difference on a loudspeaker. Results in a better understand of the actual difference.
I dissassembled yesterday a B & O MI, Type MMC 2, between the iron cross( holding the sapphire tube cantilever) and the pick up coils is just a piece of rubber and a plastic insulator carrying the rods in the coil cores.
So the rubber is dominating the whole thingie and electrical damping of the motor is veeeeeeeeeeeeery far away from reality. Mission impossible.
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As my father used to say "If you are over forty and don't feel any aches or pains when you get up in the morning, you are allowed to stay in bed all day. Because you are dead."
So happy birthday.
(Just in case anyone thought there might be anything normal about me, even my birth certificate has the wrong day on it!)
Happy Birthday Jacco.
Don't give up the medication but don't overdo it
Ed
Kinetic energy entering the cartridge
KE=0.5*m*v^2 (m for mass, v for velocity)
For
v=5cm/s (modulation velocity)
m=0.5mg (effective mass)
KE=6.25E-10 Joule
So the mechanical power entering the cartridge in 1s is 6E-10 W
A 1mV/1cm/s MM cartridge when reading a 5cm/s modulation supplies to a 47k load a P(el)=5E-10W
The mechanical to electrical efficiency seems to be ~ 80%, a very high number for such a small generator
What the electrical to mechanical efficiency is, I don't know but trying to figure it from measuring a cantilever motion when cartridge is on air while energising the coils, wil give ironically low results (the moving part of the magnetic circuit is way out of it's proper position)
I don't remember if I have measurements of a cartridge impedance vs frequency. I'll check when I'll be back home.
Ed, your father must have been a tough guy
George
Dang, again.
I'll have to reschedule the appointment to an earlier date, this is getting ridiculous.
https://archive.org/details/NetworkAnalysisFeedbackAmplifierDesign
(1945, so what would that suggest about SY)
(nice written book by Messrs. Cherry & Hooper, very coherent)
Sorry Ed the coefficient of eletro-mechanical reciprocity varies from ~0 (strain gauge) to some larger number where the point is efficient transmission of power/work. The Grado has a small metal disk weakly coupling the field of some fairly substantial neo-magnets. It's clear that if the coils were free to move and you ran current through them you might get some relay type action. The assumption of large reciprocity for any electrical motor system is a mis-conception. Lucky, I trust his computations/measurements, stated MM carts are in the tiny fractions of a percent. You can compute the work done displacing the cantilever against the suspension and the work done on the disk by 5mV, they are orders of magnitude apart.
Then think the 10Hz tone arm resonance and damping the entire system with a few mV at the coils.
Considering the complexity of the whole arm, cart, cantilever system vs frequency I don't see the effective mass telling the whole story.
I recall a review of a bargain turntable where a flexural resonance of the arm at ~350Hz showed up in the frequency response, the motor in that case is definitely working against a lot more than the effective mass you give. I would think the fact that you can easily hear the sound from the cartridge when playing an LP would beg the question that there is more going on.
George,
Another question, maybe I'm missing something, conceptually you could increase the strength of the magnet without changing its mass soon you have >100% efficiency by your argument?
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