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Why 'magnetic' cartridges?

The ones I read about didn't sound like strain guage but I suppose might have been similar.

OK, just looked it up again. The strain gauge works using the changing resistance of a metallic strip as it is deformed (stretched) whereas the force-sensing resistor uses a conductive polymer that changes resistance when compressed. Similar ideas around the changing resistance of a substance as it is deformed but slightly different implementation.
 
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Don't forget the laser turntable! It produces electric signals out from reflected light in the grooves

http://www.elpj.com/

twostyles2.jpg
 
Sonotone made high-end ceramic carts, Micro-Acoustics made "electret-condenser" cartridges (so named), that are as good as most magnetic carts. No special preamp required.
 
catman said:
Whilst I'm aware of other types (ceramic/ crystal, strain gauge types for example) that exist, it seems apparent that 'magnetic' types have the 'majority of the market' and I do wonder why they became the most common.
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G'day Felix,

I imagine that, in the early days, the magnetic cartridge had the advantage (over ceramic) that the magnet and the coil don't have to touch each other to produce a signal. Therefore, less force would be required in such a set-up compared to the need to deform a crystal. This allowed for less tracking force. Add to this the relative simplicity of the design, and the fact that the output signal from a magnetic pickup could be made to be a relatively faithful copy of the input signal (from the cutting head), and you have a winning combination.

Glad to see you "up and running" again.

Dan
 
I think that digital took over the market just as miniaturization came along.

Many technologies are possible if you can put electronics in the cartridge body.

I've wondered about a simple photoelectric system, or even a laser system the reads the movement of the cantilever. Or Hall effect.

If you have $10,000 or so, you can buy a player that reads the disk with a laser, not touching the disk.
 
Yes but reports of the Laser TT, are variable... and it is substantially more sensitive to dust and grunge than a stylus is...
It is flawed in its perfection!

The idea of electronics in the cartridge body has great merit though it requires a different setup ... it needs power for starters, so you start to have a setup that looks like the strain gauge setup - feeding a bit of current up the wires to the cartridge....

So you need both the new cartridge type, and a new phono stage type.

(not to mention several years worth of development time, and then marketing $$)

bye for now

David
 
guiller said:
Don't forget the laser turntable! It produces electric signals out from reflected light in the grooves
Click to expand...

An impressive an remarkable invention that solves something that wasn't a problem to start with: Record "wear". With modern, high-quality equipment, record wear isn't an issue at all.
 
lini said:
Felix: I guess it's simply the most obvious approach to use basically the same technology as one uses for the writing also for the reading.
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I think Lini is right on this one. AFAIK the first 'electric' cartridges were magnetic.
 
I remember that in the 70s a crystal type phono cartridge was available. It seemed that was a piezo crystal kind. It was very popular. My father had one. About the sound : quite good, there were not much variations on the model, for example for the turntable in the photo the models are : GP204, GP380, GP410. Inside there were 2 little bars of crystals, probably one for each channel.

Maybe the sound was limited because of the materials and principle of operation. In magnetic cartrigdes I think that you can make more variations in the construction to have a certain sound.

CRYSTAL-1.jpg
 
So you need both the new cartridge type, and a new phono stage type.
Click to expand...

Obviously you need a new cartridge type, but I suspect you could adapt nearly any competent stylus assembly, merely using it to follow the grooves, so that some more advanced system could translate the vibrations to line level output. I think you could attach mirrors to the cantilever, or even to the tip of the cantilever just over the diamond. You could virtually eliminate cantilever resonance as a source of distortion.

No need for any preamp other than what's in the cartridge. There would be tremendous value of putting the first gain stage inside the cartridge body. It would eliminate the most difficult aspects of matching cartridge, interconnects and preamp.

Miniature electronics don't weigh as much as magnets, so you would have room for a lithium battery. Or you could use the kind of phantom power used for microphones.
 
The laser player was developed too late for the masses.
There are a lot of records with scratches and dirt in the grooves. I guess only care and cleanliness can preserve a record.
 
If nobody would have put magnetic cartridges into production, what would they have done with all those people and machines that knew how wind those tiny little coils of wire?

\:^)

Doug
 
Could be very wrong, but I thought the first "electrified pickups" (don't know if you could call them cartridges) were carbon button, or carbon compression.
 
In the realm of magnetics, there is Moving Magnet (MM) which literally does that; Moving Iron (MI) that varies the magnetic field by interaction; then Moving Coil (MC) that reverses the idea and lets the coils move while the magnet stays still. But, all of these rely on coils and magnets to ultimately generate the current.

Strain Gauges and others may be reacting to external pressure and an already flowing current? I've always thought a powered cartridge with a DC signal going up-line to the cartridge and an AC signal coming back down would be the best solution. It would allow even more operator control and variability in the ultimate "voice" :)
 
dlaloum said:
Apparently in the 60/70's Astatic developed high end ceramics - and there are a number of lodged patents associated with that development.

David
Click to expand...

When you mentioned Astatic, I suddendly remembered this review:



It was about the Astatic MF-100 described as a "fixed-coil" cartridge (High Fidelity, January 1982)

"What distinguishes Astatic´s MF pickups is their lack of pole pieces. Instead, they have specially designed coil assemblies that detect the flux variations directly through their windings. It is this constantly changing voltage - the electrical analog of the mechanical groove modulation - that is picked up and boosted by your amplifier".
 
But the laser player needs machine cleaned records, needs declicking, and needs black flat records, which gets us to CD quality these days. So, why bother? Pivoted arms are better in real life.
 
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