Push-Pull Transformers

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Output Transformer Comparison Part 1 - Push-Pull Transformers

This article was originally featured on the "Tube Kingdom" 2003 Winter issue Vol27.  (The "Tube Kingdom" is a quarterly publication from Stereo Sound Publishing Inc.)  The title of this article was "17 Output Transformers Sound Comparison on the EL34 Push-Pull Mono-Blocks".  Mr. Tadaatsu Atarashi constructed the power amplifier, and Mr. Atarashi replaced output transformers each time before conducting the listening test.  Along with Mr. Atarashi, Mr. Hirokazu Shinoda took notes for sound characteristic on each transformer. 

Comparison Parameters

bulletEL34 (6CA7) Class B Push Pull Fixed Bias
bulletGlobal 22 db NFB from the Secondly
bullet70W+70W to drive the B&W Signature 800
bulletSoftware - Classical & Jazz CDs
bulletBeethoven Violin Sonata - Universal: UCCG1129-31
bulletBeethoven Symphony No. 9 - Phillips: UCCP9424
bullet"Jazz Piquant - Cest Si Bon" - M33JAZZ042
bullet"Rediscovered Liszt Recital" by Jorge Bolet - BMG Entertainment


Reference Equipments

bulletCD Player - Studer A730
bulletPre Amplifier - WE420A-WE396A Tube
bulletSpeakers - B&W Signature 800















Seventeen output transformers from ten manufactures were compared on this test.  These ten companies include James in Taiwan, Lundahl in Sweden, Tamura, Tango, Noguchi, Hashimoto, and others.  Hashimoto Electric sent three different models for this test; the HW40-5, the HW60-5, and the HW100-5.  Mr. Atarashi and Mr. Shinoda, both recommended Hashimoto's HW60-5 and HW100-5 along with several units from other manufacturers.   Here is a little more detailed evaluations from these two testers.

  Summary of Mr. Atarashi's Opinions Summary of Mr. Shinoda's Opinions




Clear, natural, balanced sound

Good linearity

Sounds more advanced than older Sansui transformers with flat impedance variances

Entertaining sound

Well developed Sound with Actual sound testing

Wide Dynamic Range





Feel immediate impression of good sound

As if being on live recording

Feel the passion of musicians

Feel immediate impression of good sound

Natural and realistic

Feel indirect presence of the music hall



Well-driving the B&W Signature 800

Colorful and Vivid

Three dimensional sound - as if being in live music concert

Could feel the depth of musician's expressions

More low and mid volume than the HW60-5

Best fit to modern tubes

Very vivid

Differentiate instruments

Could feel the height of the music hall with three dimensional sound


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Last updated: 02/01/15.