EL34 Triode Connection PP #1

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EL34 Triode Connection Non-NFB Push-Pull with Hashimoto Transformers - Project #1

This amplifier was originally featured on the February 2003 Issue of the "High-Fidelity Audio: Radio Technology" by Mr. Tadaatsu Atarashi.  Mr. Atarashi's goal for this project was to recreate the later version of Western Electric WE-42 Type Amplifier that was initially introduced in 1928.  The original WE-42 Type Amplifier was equipped with 205D; however, it was replaced by EL34 in 1958 via Altec Service who took over the maintenance service from Western Electric.  This modified amplifier was called the 42 AP-1, and Mr. Atarashi followed the basic design of the 42 AP-1 to construct this amplifier.

As being depicted on the schematic diagram, this amplifier is extremely simple.  Mr. Atarashi called this amplifier a single stage booster amplifier.  Besides Hashimoto HW-25-8 output transformer, PT-270 power transformer, and C-15-200CH choke coil, Mr. atarashi used an input transformer, the P-285Q from P&C in Japan. 

Mr. Atarashi used his Studer A730 CD player for the testing input source.  Then, he was planning to drive his Western Electric WE-753C Monitor Speakers with this amplifier although he was not sure which line/power amplifier he could utilize for this booster amplifier.  Therefore, He tested the 16Ohms headphone output from the Studer A730 CD player directly into the 16 Ohms input.  He also tested his mini amplifier that can yield 2.83V, 1W output into 8 Ohms input.  In either case, Mr. Atarashi was not 100% satisfied with the listening result.        

Mr. Atarashi ended his article with his promise to feature a line amplifier that could effectively drive this booster amplifier on the following issue.  However, his actual solution was a little different.  That article is explained on the following section.   




EL34 Triode Push-Pull Class A Self Bias Data Sheet (extracted from National Valve Museum site)


Opt 1 Opt 2
B Voltages: Vb 400 Volts 430 Volts
Cathode Register: Rk (Common) 220 Ohms 250 Ohms
Plate Current (0 Signal): Ia(0)  2 x 65 mA 2 x 64 mA
Plate Current (Max Signal): Ia(max signal) 2 x 71 mA 2 x 67 mA
Plate to Plate Load: RL(a-a) 5,000 Ohms 10,000 Ohms
Control Grid Voltage: Vg1 (approx) - 29 Volts - 32 Volts
Power Output: Pout 16 Watts 14 Watts
Total Distortion: Dtot 3% <1%

Schematic and Actual Characteristics

bulletSchematic & Harmonic Distortion



bulletInput/Output & Frequency Response


bulletEL 34 Data Sheet from Mullard
bulletEL 34 Data Sheet from Philips
bulletEL 34 Data Sheet from Telefunken

           Data Sheets are from Frank Philips


















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Last changed: 02/01/15

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Last updated: 02/01/15.