Hi Friends,
I would like to know how important of the resistor at base pin (Rb) in each of power transistors below schematics. Some manufacturer do the driver and output stage without this resistor like Krell FPB series power amplifier.
How it impact to sound quality or stability.
Please kindly share your opinion about this. 😕
I would like to know how important of the resistor at base pin (Rb) in each of power transistors below schematics. Some manufacturer do the driver and output stage without this resistor like Krell FPB series power amplifier.
How it impact to sound quality or stability.
Please kindly share your opinion about this. 😕
An externally hosted image should be here but it was not working when we last tested it.
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The small base resistor sets a LP filter with the output device capacitances to prevent oscillations. Slower output devices like planer or epitaxial types usually do not require base stopper resistors but faster more modern devices like RETs (ring emitter transistor) do require base stopper resistors to prevent instabilities. I recomend using the base stoppers with the MJ's.
Thanks to CBS240, That new to me and agreed with you.
So should it also necessary for a smaller transistor because of higher FT??
If you are making your own PCB, I suggest you allow space/pads for every transistor to have both base resistor and emitter resistor.
It's easy to short them out during testing to see what effect these resistors have.
It's easy to short them out during testing to see what effect these resistors have.
I dont think they are always required with fast outputs, this depends on the compensation method used and the speed of the input section, I have various Rotel models, all with triple output stages which are less forgiving and all of them are perfectly stable with no rb resistors and whats more with no output coil either. Consult schematics like rb970.
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