Comparing a single ended one transistor Pleiades BD139 to a single ended one electron tube WE417A as power music amplifiers with no negative feedback

Both are now in the same small reverberant room.


At this stage:


The BD139 operating point is 12V, 70mA
There is a very big 300B size type output transformer impedance matching say 70Ω transistor output impedance to speaker.


The WE417A operating point is 100V, 10mA
So electron control device dissipation is comparable.
The output transformer used at this stage is much smaller, about 4 times less volume of iron.
A 1:3 Sower octal base inlutbtrasformer is used.


Signal path:


producer's brain - Carlos Jobim CD, or Ray of Light - Madonna CD - Sony CD Walkman, line out bridged - one electron control device power amplifier, BD139 or WE417A - 4Ω or 12 Ω speaker, Pleiades linoleum Auratone 5C type fullrange 5in Tesla speaker or Zeis Ikon baffle fullrange 7in DEW speaker - listener's brain


Preliminary listening tests:


Carlos Jobim sounds spectacular on WE417A electron tube with Pleiades linoleum Auratone 5C type speaker. Smooth and extended bandwidth.
Changing to Zeis Ikon the sound was not much louder indicating 4Ω or close is the output impedance of power amp at this stage.
The Power of Goodbuy - Madonna with Zeis Ikon speaker did not sound impressive.
Distortion in bass possibly due to output transformer small size or 12Ω impeadnce mismatch.


The BD139 sounds at this stage about 3-4 times louder(!) than the electron tube amplifier.
Ray of Light - Madonna CD sounds spectacular, big, loud.


Great difference on power consumption. The battery powering the BD139 lasts for very long time. The battery powering the sinewave inverter which powers the WE417A amp stays on only for a while.


It is great fun listening with a one transistor power amplifier operating in class A (electrons flowing all the time) with no negative feedback filling with sound many rooms while being powered by the smallest size 12V lead acid battery.