Hiraga "Le Monstre"

stefano,

I've built this amp and i think it is very good. I don't know about a car amp though, it draws quite a bit of current Anyway if you do want to build it here's some tips: If you built this please be sure to bypass the biasing circuit of the input cascode with some good caps (or give it a really good regulator), this makes it sound quite a lot better. This is a very fast amp and to my experinece it is best to give it a psu that is build up with a large number of smaller caps in stead of one large one, a pi filter works very well and series resistance in front of the rectifier (0.33/47 OHMs) will do good as well. In the case of the mosfet version please have a look at goeff's excellent website. He has got the original articles printed there and hiraga did look at mosfets as well, there's a pcb layout to.

greetings, Joris
 
Hi,

here in Munich a lot of guys had built these around 1990, as well as the pure bipolar version "Le Classe A".

Personally, I prefer the "Le Classe A", for it does the PRAT (pace, ryhtm, and timing) thing much better, in a way otherwise Naim does. "Le Monstre" OTOH is smoother in the mid to treble region, sounding more "High End Stereo".

Where the Monster excells, is when driving 100dB horn speakers. It can be viewed as a viable alternative to a single ended triode design.

regards,
Hartmut from Munich
 
NU_NRG said:
Someone here know where we could find pictures of this amplifier?

Hi,

the "Le Monstre" was a pure DIY project in that "L'Audiophile" magazin, whereas its big brother, the "Hiraga Le Classe A" was also a commercial realisation.

I try to load a pic of a commercial "Classe A", which was the first realisation of that amp, with 20W power each channel. The later revised "Le Classe A" had up to 30W per channel, and bigger lytics in the filter stage 330 000 uF (4 times).

BTW, later years of production are much prettier.

regards,
Hartmut
 

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Hartmut and all,
agreed, the Hiraga amp had better PRaT, and "Le Monstre 8W" was more smooth and open in the mid to treble region. I had this amp running for years, making me tube nuts completely happy with it. Control in the low end was remarkable, provided listening volume was moderate.

I once heard a battery operated version, fed form 170Ah battery capacity and several Farads of PS cap capacity.
This was better than my unit, considerably, this was really something.

One warning: the input FET determining the quiescent current (by its transconductance is ultra-sensitve to electrostatic hazard; i killed my monster, performing an innocent mod (other resistor brand) and then finding the sucker sucks 4 times as much current, frying itself. :(
 
le classe & le monstre

Hi there,

Hartmut and Bernhard, did you build a complete diy version of the le classe and if so which version? I built it three times as well but never managed to get rid of some low level (but audible hum) in that design and i tried everything but nothing worked so i finally settled on the le monstre. I agree with the difference in sound, to me the le classe sounds more friendly and warm. The le monstre has an incredible detail and bass though.

Stefano, one other tip due to the large differences in behaviour of the fets the load resistor of the input cascode will probably have to be tinkered with in order to get the right standing current. more resistance is more current and the other way round. Sorry by the way for not posting the url in my first reply.

Greetings Joris
 
Re: le classe & le monstre

jazz said:
Hi there,

Hartmut and Bernhard, did you build a complete diy version of the le classe and if so which version? I built it three times as well but never managed to get rid of some low level (but audible hum) in that design and i tried everything but nothing worked so i finally settled on the le monstre. I agree with the difference in sound, to me the le classe sounds more friendly and warm. The le monstre has an incredible detail and bass though.

Greetings Joris

Hi Joris,

I had commercial 20W and 30W Hiraga Classe A at home, and there was absolutely no hum. You should check your ground routing. There are quite a lot of DIY Monsters in Munich, and all of them worked very good. Most folks I know use a regulated power supply for the Monster, which they say sound better than half a Farad of caps. The regulation is that published in L'Audiophile magazin, consisting of a zener, a small signal bipolar, and a power mosfet. I could search for the schematic and scan it, if anybody is interested.

regards,
Hartmut
 
Hi,

Harmut, thanks for you're reply I'd be very interested in the regulated psu and am sure to try it. I am currently designing a project in which i plan to build several amps in a certain style and both hiraga's are apart of this so any tips or hints are welcome. Due to the cost and complexity the project will span a couple of years though. As for that hum, I'm by now suspecting it has something to do with the casing i'm using but changing that will mean a complete redesing and has to wait for the definite plans of my amp project.

regards, Joris
 
Regulated L'Audiophile power supply for Kaneda and other power amps

Hi,

this power supply for power amps has been designed for Kaneda style class A power amps, but the voltages can easily be changed to your needs, just by changing the voltage reference, which is just a zener diode. For Hiraga, 20..25Volts each rail are good, for "Le Monstre", about 12..14 volts. As the Hiraga and the monster only idle currents in the one amp region, at least for the monster the second Mosfet can be omitted.

regards,
Hartmut
 

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