EL84 UL Push-Pull Stereo Power Amplifier with Hashimoto Transformers
This amplifier was
originally featured on the October 2003 Issue of the "High-Fidelity Audio: Radio
Technology" by Mr. Tadaatsu Atarashi. Mr. Atarashi designed this
amplifier based on the EL84 schematic diagram published by Rogers in England. Mr.
Atarashi chose this design because of the uniqueness of the positive feed back
that the original blueprint adopted. This positive feedback is
applied back to the input stage cathode from the phase splitter's cathode.
The reason why Mr. Atarashi was interested in the positive feedback was, from his past experiences, Mr. Atarashi suspected positive feed backs would yield
somewhat brighter sound than not having any positive feed backs.
For this project, Mr. Atarashi used Hashimoto PT-180 power transformer,
C-15-200CH and C-30-40 choke coils, and HW-25-8 output transformers. The
speaker system Mr. Atarashi used for his listening test was a pair of Western
Electric, WE-735C monitor speakers. EL84 power tubes were from Electro
Harmonistic. Because of the size of the EL84, Mr. Hashimoto was not
expecting to hear the powerful, but shining sound from his vintage speakers.
