View Full Version : A or AB?
17-06-2003, 12:55 PM
Hello everyone, i came across the manual for my stereo amp today(Technics SU-VZ220 about 13 years old)and i noticed that it calls it self a 'new class A' amp. I had always thought that valve amps were class A, drawing a current through the amp whether the is any input or not and running 'hot' as a result, and transistors were AB class, the flow of cuurent is turned on and off depending on the input.
i know its a long shot given the age of the amp but does anyone know what class it is or what a 'new class A' amp may refer to?( no mention of anything in the manual)
am i comletely off track with my definitions?
ive attached a scan of the 'new class A' logo if that helps
17-06-2003, 08:10 PM
I think you are slightly off track with your definitions.
Firstly, Class A operation is possible with either valves or solid state. However, high power, pure class A designs only really become feasible with solid-state. The early Krell KSA series managed to sustain pure class A operation right up to their rated outputs (up to 300W!!). Serious heatsinks and fans are required to prevent 'The China Syndrome' from occurring though :o~:-o~:eek: . The later S and FPB series manage the same feat without some of the inherent heat problems by dynamically adjusting the bias level.
While a number of the mainstream manufacturers, like Technics, jumped on the Class A bandwagon, most of them only really operate in pure class A mode for the first few watts of their output, on the basis that the sort of distortion class A is meant to eliminate is most audible at low power levels. Beyond those few watts, these devices operate as class AB.
I don't know what Technics specifically referred to as 'New Class A', but without some serious heatsinks and real heat output, your SU-VZ220 will not be operating in true class A mode at anything like its rated output, I'm afraid.. :(
17-06-2003, 08:37 PM
Charlie thanks for trying to make sense of my confusion :?~:-?~:???: i think some further reading is in order! So basiclly its an advertising gimick on the back of pedigree 'pure class A' amps?
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