Strange, one BD139 transistor can sound so loud that you might have to get out of the room

Signal path:


Promise - Sade  CD album - Sony CD Walkman line out bridged to mono - Pleiades BD139 one transistor amplifier with 100mH:25mH output transformer - Zeiss Ikon typ:31-06 baffle fullrange DEW 7in drive unit speaker - small reverberant room


BD139 operating in class A ie electrons flowing all the time.


Quiescent current is about 70mV at 12V power supply.