The Camm ValveTone Hi Fi, a cascoded valve mosfet amplifier.
This is not a fashion statement or the latest fad in the valve ”who can do it better” department, but rather a logical and uncomplicated way of using the best components for the job in hand. Valve amplifiers have inherent problems relating to power output versus low frequency cut-off of the output transformer, with consequent problems of mismatch and distortion with the loudspeaker. Lets face it, a class A, 5 watt amp trying to drive an 8 ohm 89 dB efficiency load gets you nowhere fast. Transistors on the other hand are notoriously difficult to bias correctly and with their nasty thermal runaway and slew induced distortion, not to mention their signal clipping ability, make them far from ideal devices. To overcome all of these problems, the mosfet was developed, but it too had it’s problems like their high on resistance and the awkward load they present, preventing them from being driven properly by the transistor driver stage.
So if we take a valve with it’s linear characteristics, warm full even harmonics, high input impedance and of course a distortion level some 10 times lower than a transistor and match them to a mosfet source follower complimentary output stage with their high input impedance, negative temperature co-efficient and high output power, we end up with a single gain stage amplifier, the ultimate for ultra low distortion, with very unique properties. Connect the input driver stage in cascode with the valve, and we eliminate the Miller capacitance effect and have the perfect amplifying stage that is very linear indeed. Adding shunt feedback to a virtual earth potential, holds the output at the correct voltage for maximum linear output voltage swings. Power the driver stage from a well filtered gyrator circuit giving some 70dB ripple rejection and you have the best sounding amplifier on the market.
Welcome to the Camm ValveTone amplifier.
* The name Moscode™ is used with the kind permission of George Kaye.
The moscode amplifier was invented by George Kaye, working out of the New York Audio Labs owned by Harvey Rosenberg in 1984. He and Harvey coined the term Moscode™ and owns the trademark. My amplifier bears no similarity with the Moscode™ and was designed by Jeff Macauley.
Specifications :
Power output: 80w RMS into 8 ohms.
Total harmonic distortion: < 0.1 %
Input sensitivity: 500mV for full output.
Input impedance: 47kOhms.
Finish: Solid oak, Oregon Pine or kiaat front and sides.
So if we take a valve with it’s linear characteristics, warm full even harmonics, high input impedance and of course a distortion level some 10 times lower than a transistor and match them to a mosfet source follower complimentary output stage with their high input impedance, negative temperature co-efficient and high output power, we end up with a single gain stage amplifier, the ultimate for ultra low distortion, with very unique properties. Connect the input driver stage in cascode with the valve, and we eliminate the Miller capacitance effect and have the perfect amplifying stage that is very linear indeed. Adding shunt feedback to a virtual earth potential, holds the output at the correct voltage for maximum linear output voltage swings. Power the driver stage from a well filtered gyrator circuit giving some 70dB ripple rejection and you have the best sounding amplifier on the market.
Welcome to the Camm ValveTone amplifier.
* The name Moscode™ is used with the kind permission of George Kaye.
The moscode amplifier was invented by George Kaye, working out of the New York Audio Labs owned by Harvey Rosenberg in 1984. He and Harvey coined the term Moscode™ and owns the trademark. My amplifier bears no similarity with the Moscode™ and was designed by Jeff Macauley.
Specifications :
Power output: 80w RMS into 8 ohms.
Total harmonic distortion: < 0.1 %
Input sensitivity: 500mV for full output.
Input impedance: 47kOhms.
Finish: Solid oak, Oregon Pine or kiaat front and sides.
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