Hello all,
I stumbled across this schematic while looking though some old service manuals. It is the output section of a 150W power amplifier.
I like the way it’s put together and thought I would share it for interested to use as inspiration for a new design.
\Jens
I stumbled across this schematic while looking though some old service manuals. It is the output section of a 150W power amplifier.
An externally hosted image should be here but it was not working when we last tested it.
I like the way it’s put together and thought I would share it for interested to use as inspiration for a new design.
\Jens
If leach amplifier (pretty yours) already fell down in you foot finger, you can face
The pain of a heavy class A to.... Join us Jens!, you have a lot to help!... came to us.... class A crazy guys.
No matter your intention, this gift is for me.... everyone that open their mouth to talk about class A, i feel as talking directly to me...and i became happy.
Thank you, my wish, thousand guys came here... full of ideas... with courage to expose them.... will be the best thread from long time.
Carlos
The pain of a heavy class A to.... Join us Jens!, you have a lot to help!... came to us.... class A crazy guys.
No matter your intention, this gift is for me.... everyone that open their mouth to talk about class A, i feel as talking directly to me...and i became happy.
Thank you, my wish, thousand guys came here... full of ideas... with courage to expose them.... will be the best thread from long time.
Carlos
Indeed, a bit unconventional. Output stage is normal darlington, but bias setting is via resistors R94+95. Temperature compensation via IC1 and TR28, making a temperature dependent current sink. IC1 senses the current through R91. This results in a temperature dependent bias voltage across R94+95.
I don't see the benefit of this compared to a fixed current sink and Vbe multiplier as bias voltage source, though.
Another unusual thing is the driver, TR23, which is an emitter follower instead of the more common common-emitter stage (VAS). This might result in a-symmitrical driving of the output stage. The emitter follower can supply more current (positive edge) than the current sink can sink (negative edge).
Steven
I don't see the benefit of this compared to a fixed current sink and Vbe multiplier as bias voltage source, though.
Another unusual thing is the driver, TR23, which is an emitter follower instead of the more common common-emitter stage (VAS). This might result in a-symmitrical driving of the output stage. The emitter follower can supply more current (positive edge) than the current sink can sink (negative edge).
Steven
Is'nt this just a current loaded buffer, maybee also a current loaded VAS stage before this ? The mpsa 13 the current limiting transistor for the active load. Probably its class A. 1,1-1,2v ube. near 12 mA in tr23 There is many ways to achive class A and this is just one of many for many different stages. As such it dont seem to have any (significant) advantage over other commonly used low open loop gain/low lockal feedback in the output stage.
BUT : if the current limiting transistor also has temperature feedback as it will. And the overall dc performance is achieved thru overall feedback, but is most definetly coupled thru temprature. But then it will alter the biaspoint also for the innput stage as temperature alters. If class A is the goal there will still bee 'small' changes. ie sin tone to full output at klass A settup load the temp in the output stage would make a small drop (for most commonly designed class A stages). And again altering the reference bias point for the input stage, as balance is concerned dependent the rest of circuit. For the buffered stage altering the constant load and for the output stage the bias is altered. Hopefully this is most elegantly designed and stable, this is werry hard to achieve and i sertainly dont tink it is possible under all the varius loads and enviroment.
BUT : if the current limiting transistor also has temperature feedback as it will. And the overall dc performance is achieved thru overall feedback, but is most definetly coupled thru temprature. But then it will alter the biaspoint also for the innput stage as temperature alters. If class A is the goal there will still bee 'small' changes. ie sin tone to full output at klass A settup load the temp in the output stage would make a small drop (for most commonly designed class A stages). And again altering the reference bias point for the input stage, as balance is concerned dependent the rest of circuit. For the buffered stage altering the constant load and for the output stage the bias is altered. Hopefully this is most elegantly designed and stable, this is werry hard to achieve and i sertainly dont tink it is possible under all the varius loads and enviroment.
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