(C) The Original Outstanding Valfet Audio Power Amplifier.


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"The Original Outstanding Valfet

Audio Power Amplifier."


The author and designer of the (C) Valfet Audio Power Amplifier is Anthony Johns. For legal reasons in the time period 1992 - 2002 for three of the books that the author has written: he uses the pseudonym of (RTM) Tim Marsh. This book about the evolution of the design of the (C) Valfet Audio Power Amplifier is now in the name of Anthony Johns.

This book takes you through the authors interest in music reproduction, and the evolutionary designs of audio systems that he built and used while the interest progresses. The author, Anthony Johns is still very much interested in audio design, and two of his final designs as well as his evolutionary designs are published here.

There are eighteen schematic diagrams with explanations pertinent to the presented evolutionary designs, together with colour photographs of the (C) Valfet Audio Power Amplifier exterior and Interior. Thermionic valve reproduction by far surpasses transistorised designs.

This power amplifier is extremely different, in that it uses a separate valve signal amplifier to provide the clean high voltage drive that is required for the high power unity gain buffer ( source follower ), that drives the loudspeaker in class A to Seventy Five watts RMS full output, and in class B to One Hundred and Fifty watts RMS full output. The topology for the Valfet Audio Power Amplifier, is shown below.

The Valfet Audio Power Amplifier - Topology.

As can be seen from the diagram below, the valve stage is a separate high voltage signal amplifier, connected to a solid state unity gain buffer that drives the output transistors and then the loudspeaker. There is no conventional comparative negative feedback from the loudspeaker to the input stage.

Although the topology is a novel feature of this amplifier, this feature was not added for it's novelty value. This amplifier design is the product of many designs evaluation, and the final design was found to be sonically superior.



The Valfet Audio Power Amplifier - Cabinet.


The Valfet Audio Power Amplifier - Chassis.

As can be seen below there are compact plug in cards that plug in to the mother board. The ECC83 Valve is shown to the right.


This amplifier was reviewed in the June 1989. Hi-Fi News And Record Review magazine, the review regards the sonic virtues of the amplifier was very good indeed. The reviewer Ken Kessler did not like the amplifier case which was aesthetically designed for the British market or the price, the price was high to account for the development costs of a new moulded aluminum eight segment round amplifier design.


To read Ken Kesslers outstanding sonic review please click on the review link below.

Review.

     FOR FURTHER INQUIRIES,
     WRITE TO,

     A.W.JOHNS.
     34 BISHOPS HILL.
     IPSWICH.
     SUFFOLK.
     U.K.
     EUROPE.
     IP3 8EN.

     TO E-MAIL,
     PUT AMPLIFIER IN THE
     SUBJECT LINE.
valfet@ntlworld.com


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(C) The Valfet Audio power Amplifier.

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The New Valfet Audio Power Amplifier.

The Original Valfet Audio Power Amplifier.

Damping Factor Is Fully Explained Here.

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