simple Class A amp

[muddasirwaheedmalik]

hi ,

i intend to use this cirucuit for class A amp, using 2SA2921/2SA1215; 150W Pd transistor pairs salvaged from old sony power amps.

i intend to run it on batteries, sealed 150 AH type, in series giving +/- 12V rail voltage. with 5 Amp draw constant i will get around 20 hours playback time easily , although i intend to use it for 2 hours at one go max.

Pd at each rail would be 12V x 5A=60 watts continuous, and about 1-2 Ampere of load current which will give me around 15 W Class A amp. (idea taken from triple pair used in Luxman amp giving 42 w Class A amp ) but for beginning i would be using 12/24V Lambda power supplies 53A capable , so i could use more output pairs with these switching power supplies.

The design would be like this:

[AndrewT]

IC1 will be ClassAB.
None of your transistors are fitted with emitter resistors.

[muddasirwaheedmalik]

thanks, its a random thought at the moment, IC1 needs to be replaced by input stage in class A, the reason for absence of emitter resistor is self protection of high bias output stage and for lowest possible output impedance pushing up the damping factor or bass quality, the krell way i suppose.

Btw any recommendation on operating volt +/-12 or +/-24 volt selection and input stage in class A with discrete components. (As mentioned earlier i have 2 SMPS supplies with 50A constant capacity industrial grade Lambda, so can dissipate a lots of idle current with multiple devices in parallel say 10 pairs on each side disspating 4 A current ).

Can it be designed for transformer coupled single ended class A ???

[AndrewT]

Originally Posted by muddasirwaheedmalik

the krell way

Krell use emitter resistors.

[muddasirwaheedmalik]

thanks for correction, but it uses Pull push design, i think for single ended contanst current/resistor bias this would not be required. any link/design for one/two stage Class A single ended design , the efficiency is irrelevant here design should be simple, possibly no coupling capacitor ???

[AndrewT]

PASS.
One of the best ClassA instruction sites in the www
Maybe the "best".