The Class-A Amplifier Site

This page was last updated on 19 July 2004

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Jean Hiraga Class-A Amplifiers



The following two designs by Jean Hiraga were originally published in the French magazine “l’Audiophile”. They have a good reputation for sound quality, but this is not an aspect I have been able to verify personally. Unfortunately, I am unable to offer any support for these designs since I have yet to build either of them, but if anyone else has useful information relating to these amplifiers, for example transistor substitutes, please let me have the details and I will add them to the ‘Additional Information’ page.


It now seems unlikely that I will ever get round to completing the translation of the articles, due to ill-health and other priorities, so I have added copies of the original articles for the benefit of anyone who can read French. For those who can’t read French, approximate (machine generated) translations of sections of the articles can be obtained using the on-line facilities at SYSTRAN.


My thanks go to Rudy van Stratum for sending me copies of the Hiraga 20W Parts 1 and 2, to Scott Nixon for the Hiraga 20W Part 3 (and to Jam Somasundram for arranging this) and to Mike Jonasson for the copies of the ‘Monster’ articles. I would also like to thank Miroslav Vujica for supplying a draft translation of the 20W Class-A Part 1 article.





The 20W Class-A


Last Updated



Part 1 –  Conception générale


7 August 2001

Part 2 –  Construction


8 August 2001

Part 3 – La version définitive 


1 August 2001



Part 1 –  General design  (l’Audiophile No. 10)


19 July 2004

Part 2 –  Construction  (l’Audiophile No. 11)


9 August 2001

Part 3 – The final version  (l’Audiophile No. 15)


19 July 2001

The Monster





Amplificateurs classe A 8 watts « Le monstre »


1 August 2001

Amplificateurs 8 W « Le monstre » L’alimentation


1 August 2001

Retour sur le 8 W « Le monstre »


1 August 2001



Class A Amplifier 8 watts "Le monstre" (The Monster)


November 2012

The Monster - Power Supply (l’Audiophile No. 29)


November 2012

‘The Monster’ Revisited  (l’Audiophile No. 31)


16 July 2001



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HISTORY:   Page created 05/07/2001

10/07/2001 20W Class-A split into 3 parts

12/07/2001 Figures added to all articles

14/07/2001 Text added to Hiraga 20W Part 3 article

16/07/2001 Text added to Return to the Monster page. Minor corrections to Hiraga 20W Part 3 article

19/07/2001 Figures 4 and 5 added to Hiraga 20W Part 3 article. Figure 10 moved to separate page

01/08/2001 Original articles for the 20W Class-A Part 3 and ‘The Monster’ added

07/08/2001 Original article for the 20W Class-A Part 1 added

08/08/2001 Original article for the 20W Class-A Part 2 added

09/08/2001 Translation of 20W Class-A article Part 2 added

14/11/2001 Transistor Substitutes page added

27/04/2004 Transistor Substitutes page deleted

19/07/2004 Translation of 20W Class-A article Part 1 added