EL34 Triode Connection PP #2

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EL34 Triode Connection Non-NFB Push-Pull with Hashimoto Transformers - Project #2

This amplifier was originally featured on the March 2003 Issue of the "High-Fidelity Audio: Radio Technology" by Mr. Tadaatsu Atarashi.  On the previous February 2003 issue, Mr. Atarashi featured a single-stage booster amplifier that could drive Western Electric WE-753C Monitor speakers.  Because Mr. Atarashi did not have an adequate line/power amplifier to drive this booster amplifier, Mr. Atarashi concluded the previous article with his promise to feature a line amplifier on this coming issue.  However, Mr. Atarashi changed his mind, and he redesigned the booster amplifier itself into a full-blown power amplifier.     

The difference between these two amplifiers is the gain stage between the input transformer and the output stage.  This gain stage consists of a single E80CC miniature tube, and yields about 20 times of amplification.  With this gain stage, this amplifier improved the input sensitivity to 1W output at 0.18V.   

In addition to the original six transformers, Mr. Atarashi added one more choke coil, the EXO-99, from MagneQuest to this amplifier.  Although this amplifier does not have any negative feedback, the THD is kept under 0.1% with 1W output.  The frequency response, 20-70,000Hz (-3dB), was remarkable accomplishment for an amplifier equipped with input transformers.  Mr. Atarashi reasoned all of these excellent statistics to the quality of Hashimoto transformers.

At the listening test, Mr. Atarashi compared the sound of this amplifier to that of the original 42AP Type.  He heard the basic characteristic of the sound about same; however, he felt this amplifier reproduced a little more realistic atmosphere.  He concluded this article as, "As I always emphasize, amplifiers are nothing more than a tool to listen to music.  .... Audio equipments should be evaluated with their ability of how much musicians' emotions and feelings could be delivered from."



EL34 Triode Push-Pull 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.