6AQ5W/6005 Single-Ended 4Ch

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6AQ5W/6005 UL Single-Ended 4Ch Power Amplifier with Hashimoto Transformers

This amplifier was originally featured on the January 2004 Issue of the "High-Fidelity Audio: Radio Technology" by Mr. Tadaatsu Atarashi.  Mr. Atarashi designed this amplifier for the multi-channel SACD application with just four-channels instead of the normal five.  As Mr. Atarashi believes that the four-channel sound image without the center speaker sound more natural than that of five-channel, he used the Marantz SA-17S1 Super Audio CD (SACD) player with the Phantom Center mode (the center channel signal is divided into right and left channels)  for his input source.

Each channel on this amplifier is driven by single-ended 6AQ5W with UL (Ultra Linear) connection (3W per channel output); therefore, the H-507S (rated 7W) output transformer from Hashimoto could have been adequate.  However, Mr. Atarashi rather used a stepped up model, the H-20-7U (rated 20W at 50Hz) because he thought the H-20-7U might show an edge on the frequency response.  The H-20-7U output transformer is called the universal type because it's designed to be able to used for either 5K or 7K Ohms primary impedance.  The H-20-7U is also designed to be used under three staged amplifications, such as the input, the driver, and the output stages.  Therefore, Mr. Atarashi connected the overall negative feedback from the grounding terminal of the secondary in order to maintain the correct amplification phase (this amplifier has only two amplifying stages).                          

Mr. Atarashi concluded his article with, "The sound of Ultra Linear connection (of this amplifier) is clearer and more settled than the sound of the Beam operation (he tested under the beam operation).  Although the output is cut by 1/3, the sound quality outweighs the loss of power.  Since this amplifier is designed for the four-channel operation, you can enjoy the enough music power through four-channels even if output per channel is rather small.  I realize that the most important factor of amplifiers is not the power, but the ability to reproduce the quality of sound."     



6AQ5W/6005 Single Ended Class A1 Data Sheet

 * 6AQ5 is a miniaturized 6V6-GT

Plate Voltage 250 Volts
Screen Voltage 250 Volts
Grid-Number 1 Voltage -12.5 Volts
Peak AF Grid-Number 1 Voltage 12.5 Volts
Plate Resistance, Approx. 52,000 Ohms
Transconductance 4,100 Micromhos
Zero-Signal Plate Current 45 Milliamperes
Maximum-Signal Plate Current 47 Milliamperes
Zero-Signal Screen Current 4.5 Milliamperes
Maximum-Signal Screen Current 7.0 Milliamperes
Load Resistance 5,000 Ohms
Total Harmonistic Distortion, Approx. 8 %
Maximum-Signal Power Output 4.5 Watts

Schematic and Actual Characteristics

bulletSchematic & Harmonic Distortion (UL & Beam)




bullet6AQ5 Data Sheet (PDF Format) from GE

           The Data Sheet is from Frank Philipse Home Page



















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Last changed: 02/01/15

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Last updated: 02/01/15.