Doug Self Blamless Class B Amp


2005-08-13 6:12 am
I am trying to simulate the Doug Self Class B Blameless Power Amp Design.However with an input signal of 1V at 1KZ I am getting the same at the output. Can anyone tell me what i might be doing wrong.Thanks.


  • Doug Self Blamless Amp Design with scope.jpg
    Doug Self Blamless Amp Design with scope.jpg
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Paid Member
2007-09-15 8:14 am
As I recall C12 was marked as 100pF in the documentation supplied with the PCB's and certainly my examples I built (on the official boards) were unstable and oscillated continually with that value fitted. I think 15pF or 18pF was the value used in the original magazine articles.
There was an LTspice simulation of Doug Self's 50W amp recently in post 5 here Simulation: Cyril Bateman's Amplifier-Speaker cable interactions

In that thread PB2 (Pete Basel) was trying to replicate Cyril Bateman's bench test with a speaker cable using Doug Self's amplifier that self destructed due to a strange RF oscillation.from the speaker cable and amp interaction.

PB2's simulation did not oscillate with a simple (lumped) cable model. So it needs more work to replicate the cause of oscillation so the problem can be understood. Cyril did not find the reason before passing (RIP).