Most phono catridges are passive transducers, where a small signal voltage is generated by stylus movement. The higher the output needs to be, the greater the tracking force. Back when in the 1940s microgroove discs first appeared, I don't know about today, this approach required a tracking force as great as 5 gramms.
But in the 1950s, when microgroove discs were all still mono, a small company called Weathers did make an active phono cartridge. This used a variable capacitor attatched to the stylus cantilever. Microphones working on the same principle, all introduced later, are called RF condenser microphones, and either the diaphram capacitance is part of the oscilator circuit and modulates the oscilator resonant frequency, or a separate oscilator, such as a crystal one, generates a fixed frequency and the variable capacitor somehow modulates the carrier, I've heard it's the phase that it modulates.
The Weathers phono cartridge was like the former type, and I've heard it couldn't work for stereo because it would require two oscilators and there would have been interference between them.
But a stereo version working like the latter type of RF condensor microphone would only need one oscilator with the cartridge capacitance detuning a pair of demodulators, would this have worked?
Other stereo cartridges of the time, these being passive and with considerable moving mass, were prone to stylus bounce, part of the reason why stereo records of the sixties had a weaker sound with less bass and treble than mono ones.
Another type of active cartridge is the strain gauge, which appears to have be introduced in the 1970s and actually still made today. It appears to work for stereo, but requires a non-standard pre-amp, obivously not a problem if turntables manufactured since they were introduced had such pre-amps built into them.
So what if active cartridges had actually caught on, at least for parallel tracking turntables, and all new turntables since they were introduced, at least parallel trackers, had been designed with such things in mind?
But in the 1950s, when microgroove discs were all still mono, a small company called Weathers did make an active phono cartridge. This used a variable capacitor attatched to the stylus cantilever. Microphones working on the same principle, all introduced later, are called RF condenser microphones, and either the diaphram capacitance is part of the oscilator circuit and modulates the oscilator resonant frequency, or a separate oscilator, such as a crystal one, generates a fixed frequency and the variable capacitor somehow modulates the carrier, I've heard it's the phase that it modulates.
The Weathers phono cartridge was like the former type, and I've heard it couldn't work for stereo because it would require two oscilators and there would have been interference between them.
But a stereo version working like the latter type of RF condensor microphone would only need one oscilator with the cartridge capacitance detuning a pair of demodulators, would this have worked?
Other stereo cartridges of the time, these being passive and with considerable moving mass, were prone to stylus bounce, part of the reason why stereo records of the sixties had a weaker sound with less bass and treble than mono ones.
Another type of active cartridge is the strain gauge, which appears to have be introduced in the 1970s and actually still made today. It appears to work for stereo, but requires a non-standard pre-amp, obivously not a problem if turntables manufactured since they were introduced had such pre-amps built into them.
So what if active cartridges had actually caught on, at least for parallel tracking turntables, and all new turntables since they were introduced, at least parallel trackers, had been designed with such things in mind?
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