Κώστας Φ.
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- Μηνύματα
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Τhe GEM is an audio power amplifier embodying simultaneously active Class A and Class AB output stages. To aid construction, a universal 'star connection' pcb capable of accommodating either plain or low ESR radial or axial electrolytic capacitors has been developed, and it may be used to construct 25W - 200W conservatively rated loudspeaker driving amplifiers according to individual choice.
The circuit developed out of some 35 years of on/off investigations into the John Linsley-Hood, MIEE, 1969 class-A amplifier
...
During the 1970s the Quad Hi-Fi company patented their '405' Current Dumping design. It remains as powerful, good sounding, compact and reliable as it was then, and so remains a decent second-hand buy. I used one myself and marvelled at their theoretical ingenuity, though for me the 2x KT88 Leak TL50+ still provided better dynamic reproduction. Since then the Current Dumping circuit has been repeatedly refined for professional or home use, and yet whilst updated models remain available today, so too does a more recently released Quad 2x KT88 II-40 monoblock chassis, and for 2007 - a 4xKT88 Quad II-Eighty !!!!! That Current Dumping circuit cleverly combines both class-B and class-A output stages via a reactive output bridge which allows for the slower class-B switching. With my own circuit however, I have combined both class-AB and class-A outputs in real time, this to provide powerful audio reserves with a class-A like cleanliness, whilst retaining the kind of transparency at higher output powers more often associated with expensive push-pull triodes or the ultralinear kinkless tetrode (KT) designs. (Prior to this my favourite/reference power amplifier had been my own 1975 homemade hybrid 100Wmax 4x KT88 UL push-pull AB1, with SS differential input/phase splitter feeding a pair of ECC82s, each one running as a gain stage plus cathode follower per push-pull half.).
Class-A//D is a possibility, but that would seem to be a contradiction in terms of both complexity and modal efficiencies.
Circuit author: Graham Maynard
LINK
The circuit developed out of some 35 years of on/off investigations into the John Linsley-Hood, MIEE, 1969 class-A amplifier
...
During the 1970s the Quad Hi-Fi company patented their '405' Current Dumping design. It remains as powerful, good sounding, compact and reliable as it was then, and so remains a decent second-hand buy. I used one myself and marvelled at their theoretical ingenuity, though for me the 2x KT88 Leak TL50+ still provided better dynamic reproduction. Since then the Current Dumping circuit has been repeatedly refined for professional or home use, and yet whilst updated models remain available today, so too does a more recently released Quad 2x KT88 II-40 monoblock chassis, and for 2007 - a 4xKT88 Quad II-Eighty !!!!! That Current Dumping circuit cleverly combines both class-B and class-A output stages via a reactive output bridge which allows for the slower class-B switching. With my own circuit however, I have combined both class-AB and class-A outputs in real time, this to provide powerful audio reserves with a class-A like cleanliness, whilst retaining the kind of transparency at higher output powers more often associated with expensive push-pull triodes or the ultralinear kinkless tetrode (KT) designs. (Prior to this my favourite/reference power amplifier had been my own 1975 homemade hybrid 100Wmax 4x KT88 UL push-pull AB1, with SS differential input/phase splitter feeding a pair of ECC82s, each one running as a gain stage plus cathode follower per push-pull half.).
Class-A//D is a possibility, but that would seem to be a contradiction in terms of both complexity and modal efficiencies.
Circuit author: Graham Maynard
LINK
