Mosfet 25W F5 class A amplifier w/ improved symmetry partial assembled kit !

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Note on 24 May 2018 : From now on we shall offer IRFP240/IRFP9240 as output mosfet instead of Fairchild mosfets since the latter one has been obsoleted for a number years and our stock has been ran out.

This is one piece of partially assembled high end class A MOSFET power amplifier, with reference to the refined version of the popular F5 amplifier. In this improved design, the symmetry of the upper and lower half of the circuit is optimized by adding in a variable resistor to compensate for the N-ch and P-ch JFET discrepancy.

The board is partially assembled as the small power transistors are already soldered to minimize the assemble time. Other components that require soldering are as shown in the picture. These includes :

1. Hard-to-find Toshiba 2SK170/J74 JFETs one pair,

2. Panasonic and Dale power resistors,

3. Zetex transistors,

4. multi-turn trimmers,

5. long lead thermisters for effective thermal coupling to the MOSFETs,

PCB board thickess : 2mm

Copper trace thickness : 75um( four times standard thickness !)

Surface finishing : double-sided solder resist and gold-plated for maximum reliability.


PCB dimension : 105mm x 62mm

This is a single channel amplifier kit. Two kits are needed to form a stereo amplifier. The fully assembled board in the last picture is for reference. The kit contains a partially assembled board and a list of components as shown in the listing.

We provide schematic and part list to buyers by EMAIL( to be attached to the shipment notice).

We also have the power filtering board with reference to First Watt amplifier series that is a perfect match with this amplifier board. Please check our other auctions.