Trying frequency selective negative feedback on a Pleiades single ended class A BD139 power amplifier

It works.


4.7nF (from a Heathkit capacitor selection box) was connected between collector and base. There was distortion but then instead of connecting to bass the capacitor was connecte to CD player line out. So between the capacitor and bass is the series volume dropping resistor.


Signal path:


Ingenue - K. D. Lang, CD - Sony CD Walkman, line out, Pleiades BD139 power amplifier with frequency selective feedback - Zeis Ikon typ:31-06 speaker - reverberant room - listener's brain


This capacitor resistor combination removed excessive high sequence detail when connecting the Zeis Ikon 31-06 (small baffle full range cinema projection cabinet monitoring speaker).