Help for an Hiraga Monster project

Hi , Everyone ,

I have heard The Monster Amplifier from Jean Hiraga a few years ago an wish to build it .Does anyone have ever build that one ? If so , what would the specs. be for the heat sinks for it . I have just fund an incredible site that has the original arcticle , (and in french too ) that was published by Hiraga himself in the seventies , but missing the info on the heatsinks . And yes , that would be my first Diy solid state amplifier project .

The original Hiraga articles specify a quiescent current of 0.5A to 0.6A. With a supply rail voltage of +/-12V, this gives a maximum dissipation in each output transistor of 6W to 7.2W. Allowing for a maxumum junction temperature of 100degC, an ambient temperature of 30degC, a junction to case thermal resistance of 1.5degC/W and a case to heatsink thermal resistance of 1.5 degC/W, a 7degC/W heatsink is required for each output device (or 3.5degC/W for each amplifier).

However, if funds permit, I would suggest using larger heatsinks than this (say 1.5 to 2degC/W for each amp)since the smaller heatsinks will be at a temperature of about 50degC above ambient(which is rather warm :). The larger heatsinks will also allow the quiescent current to be raised, if required and if the power supply is adequately sized or the battery option is used, to defer the onset of Class-AB working when supplying lower impedance loads.


[Edited by Geoff on 11-15-2001 at 05:31 PM]


2000-11-24 12:02 am
I have build this amp about a year ago, and still have it.
The input FET's are a bit hard to find and their is much variation in their spec's. Also, I was not able to find a suitable replacement. Variation in spec's is such that you will have to adjust the 1K resistors (in my case lowering the value to about 680 Ohm) in the collector of the 2sc1775 and 2sa872.
I found this unit not to easy to build.
I also was a bit dissapointed with the final result. (Sound quality not to my liking)
There certainly are better amps for the same cost that you can build.

thanks for the info

Thanks to both of you for the info , and Geoff ,keep the good work . Your web pages are real worthy , I am francophone and I can't tell you how pleased I was to find the articles offerd in french . A local Electronic Institute here , had all the Issue of the " REVUE du SON " and I used to go there to consult them ... They've trowned them all !!!!

As for Mr. rtirion thank you for your comments , and would sure like to know what disapointed you , the whole design of the montstre is sure exotic and not to everyone's liking
but I heard one in france with Quad electrostatics and Elipson "boules" , and at that time I was quite impressed

Thanks again to both of you


2000-11-24 12:02 am
The Monstre I build sounded a bit thin. Lots of detail, good voices, strings. Low end is lacking. Needs speakers with more than average sensitivety. I have listened to it on BW801, VVOX Dingo, VVOX Habaria, Solosound ESL.
The depth of the sound image is very good. Mind you, all of this is pure subjective.
If you are looking for a detailed and almost clinical amp, the monstre is for you. If however you like a little warmer sounding amp, try something else.

Have a look at
<a href="">hiraga amps</a>

you might find <a href="">Hiraga Transistor Substitutes</a> Says his quiescent current is about 1.5A?

<a href="">borbely audio</a> has both JFETs, and will math them foe +50%
2SK147GR/BL/V euro10.30
2SJ72GR/BL/V euro15.40