Push-Pull Transformers

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

EL34 (6CA7) Class B Push Pull Fixed Bias

Global 22 db NFB from the Secondly

70W+70W to drive the B&W Signature 800

Software - Classical & Jazz CDs

	Beethoven Violin Sonata - Universal: UCCG1129-31
	Beethoven Symphony No. 9 - Phillips: UCCP9424
	"Jazz Piquant - Cest Si Bon" - M33JAZZ042
	"Rediscovered Liszt Recital" by Jorge Bolet - BMG Entertainment

Reference Equipments

	CD Player - Studer A730
	Pre Amplifier - WE420A-WE396A Tube
	Speakers - B&W Signature 800

Schematic

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
Hashimoto HW40-5	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
Hashimoto HW60-5	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
Hashimoto HW100-5	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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