Hiraga Le Monstre 2024

Amazingly, 40 years on, one can still find plenty of DIY examples on the internet.
It has been on the to-do list for long.
And finally we got round to it ourselves, with 4 different version.

240524 Le Monstre Deluxe Proto #1.JPG




  • Hiraga Le Monstre 2024 Description.pdf
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And the ABx Switch Box specially build for comparing different versions on the fly.
In the event that you get bombarded with requests, I'll ask openly in the forum...

I recognize with everything you share with the community, that you also have a commercial business, and this may wind up as a commercial product, but just in case...

Would you be willing to share a schematic/parts list and/or common board files used for PCB manufacturing? From your description above and your attachment, I don't feel like a "build" guide per se is needed. With the information / links you provided to your MOSFET speaker protection and the basic description of the circuit I think I could successfully build it and have an understanding of how it works.

The one thing (for now) that I am not sure I'd have an immediate / elegant solution for is level matching between amps with different gain, but I can solve that. Also, if you could share if there are practical power ratings (i.e. don't be a doofus and try to put X Watts through it), that would be appreciated.

Thanks in advance for your consideration. I'd love to compare my F5pi / M2OPS / F5m variants and many others (Tombo's Ultimate Low Power Class A / Lynn's HG etc.) using something like this. Swapping speaker cables and interconnects back and forth is a hassle... some say that I need to allow 30 mins for warm up... and I often ask others' opinions during listening (not even a single-blind opportunity).

Thank you for considering sharing yet another of your designs... If you have plans for a GB in the works or a way to recoup some of your development costs, I'm all ears.

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By the way: listening experience shows that an exact level adjustment is not necessary. In most cases, the sound characters are clearly different, and it cannot be said, as example:
A sounded slightly quieter, grayer and more overcast than B.
A also sounded slightly louder, grayer and more overcast than B.
At the same level, A would have sounded the same as B;-)
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The schematics is the original Hiraga as in the first picture of the pdf.
All the details of the other versions are fully described in the article.
Anyone can easily follow and build their own.
You have a wide selection of PCBs on the internet to choose from.
And there are also offers for GR grade JFETs as well as ALL BJTs.
I have also described how to use BL grade JFETs.
You need nothing from us.

A commercial business is one that someone can live on.
Any income we have generated from GBs have always been reinvested in equipment and future projects.
It will never pay for the time and effort we spend on these projects.
So at most you can classify this as sponsored hobby.
Luckily all of us have very well paid full time jobs.
So that we can freely choose how we go about this, irrespective of any trends or public responses.

If there will eventually be a GB, it will be because we have something to offer that you can't get elsewhere.
And as said, you don't need any of those to start building your own.

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The relay in my ABx Switch Box is my intellectual property.
I shall not publish anything for others to copy freely.
MOSFET relay circuits can be found easily on the internet.
One good example :
Fig. 2.1

Just treat it as a SPST switch.
There are 8 of those in my switch box.

And of course it is much easier and less costly with just 2x DPDT relays.
Any DIYer can manage that.

The different versions we are going to compare have the same gain.
So no need for level matching.

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As a tribute to Mr. Hiraga, I have converted the PCB layout in his original article from graphics into Gerber.
So now anyone can build 100% according to the original, without needing anything from us.

Le Monstre PCB.png

I have put copper on both top and bottom, identical.
If you wish to have single layer only, just remove th top copper and top resist from the Zip file.
And inform the PCB shop.

Disclaimer :
I have not built with this, only visual check against the original.
Use at own risk, and feel free to check against the original pictures attached here.




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A tip regarding picture 4, upper post:
Don't use fat copper plates for the rails and ground! That sounds terrible - it disregards the definition of current. Just use single core, maximum 1 mm diameter. For capacitors with screw terminals use plastic screws. This reduces the conductive contact area, which benefits the definition of current.

And: a Le Monstre can also be built without a pcb. This would also bring further sonic advantages: Contacts are reduced, lengths are shortened, deviations from circuits are reduced and more.
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In DIY, everyone can decide what to do for himself.
What we post here is our experience, with reference to the Hiraga original.
Nothing more, nothing less.

Plenty of other discussions in the original thread in all aspects, including individual favours and many recommendations for other builders :

Maybe that is a better place to centralise all such discussions ?

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