Hiraga Monstre 9W-15W pure sound Class A amplifer kit

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Note on 25 Sept 2014 : Based on some customer feedback, we have change the collect resistors to non-inductive 1 ohm 5W type.

Note on 5th May 2014 : Due to the scarcity of 2SJ74 P-channel J-FET, and the announcement of obsolete of 2SK170 N-channel J-FET recently, we inevitably have to rise the price of the kit. Even the price is raised, the supply of these already-obsoleted JFET is extremely limited and we can stop the kit at any time so please seize the chance to get it !

Note on 4th March 2013 : The power transistors are changed to On Semiconductors NJW0302G/NJW0281G. They are far superior to the older Toshiba and Sanyo transistors in terms of high current (Ic@1A~2A) amplification linearity and are better alternatives to be used in class A amplifier. We will update the pictures as soon as possible.
Note on 4th March 2012 : The kit is back to stock. Since the launch of the kit in 2009, over 500 sets were sold !!
Note on 22nd August 2011 : The power transistors are changed to Sanyo. These are proven replacement of Toshiba. ( Pictures will be updated soon)




This is a kit of class A amplifier with ultra-fi sonic quality. The design is with reference to the legendary design by Jean Hiraga. This amplifier is the Le Monstre version that can deliver 8 to 15W of pure class A amplification at uncompromised sound performance.


The kit comes with superior quality components:
1. Dale non-magnetic metal film resistors ;
2. Toshiba low noise J-FETs 2% Idss MATCHED 2SK170/2SJ74 ;
3. Low Cob Hitachi2SA872/2SC1775 and 2SB716/D756 ;
4. On Semi Power transistors NJW0302G/NJW0281G - these modern transistors has superb current amplification linearity across the high current region and is the better candidate for class A amplifier application than the old and obsoleted Toshibas'( pictures will be updated soon);
5. Nichicon KZ MUSE( or Elna Slimic II) filtering capacitors. ( One of the best caps for audio decoupling!)
6. Japan-made non inductive power resistors.
We provide schematics and part list to the buyers by EMAIL, normally attached with the shipment notice.


This is an auction for an unassembled kit. Two are needed to form a stereo amplifier. The assembled board picture is for reference.


We also have heavy duty power supply boards in other listings that diyers can put in their favorite filtering electrolytic capacitors. Please check our other listings.




PCB thickness 2mm. PCB dimension 82mm x 101mm. Copper Thickness : 70um( 4 times normal thickness !)