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Hiraga "Le Monstre"
Hiraga "Le Monstre"
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Old 5th February 2005, 10:44 AM   #31
apolon34 is offline apolon34  France
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I've already made a monstre. You can find all details on my website:


the pcb is near the same as yours. I used some power resistor in TO202 case, directly on heatsink with the BJT's.
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Old 5th February 2005, 11:34 AM   #32
jacco vermeulen is offline jacco vermeulen  Netherlands
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I have had a second hand commercial 30w Hiraga, for a large part because it is so beautifull.
Also i built a number of L'audiophile designs; the Preamp of Akihito Kaneda, Le Monstre, L'Ampli Fou.
I even made an effort on the Nemesis, a reason for reading Susan Parker's work with interest.
pcb's and most of the parts i got from the L'audiophile store in Paris, in those days in the Rue de Belfort.

The comparison between Jean Hiraga and Nelson Pass designs is not just i think.
I had the commercial Jean Hiraga JH50 PushPull tube amplifier on ESL's for a couple of days, my ears thought it to perform much better on Quads. Should be, cost a heap more than the 30 watter Hiraga.

I own an Aleph Null, bought it when only ocassionally a second hand commercial Hiraga was offered on sale in an audio store.
I built Aleph 4's, currently adding a number more.
So, i need not mention my preference.

Le Monstre i heard in the L'Audiophile store on typically French very high efficiency speakers, its a brilliant amplifier as the Hiraga is.
To me, putting Le Monstre in a car is the same as the difference between class A and class AB Mosfet amplifiers.
Try stuffing a high efficiency speaker system in a car, supposing you can then savor the beauty of the amplifier over the sound of the motor running and bad vehicle acoustics.

For enjoyment i drive a Chevy van with raised roof. I am 6'2" and able to stand in the 15' x 6.5' livingroom of the car.
The V8 only runs 1500 rpm when doing 60 mph, i can not hear the airco humming.
It has double 4 channel modified amplifiers, for a large part biased in class A with multiple decade MHz Sanken ringemitter output devices that tap from an added battery and two 1 Farad caps.
Sounds quite nice, but i bet a Le Monstre in a regular home on +100 db/watt quality units sounds a lot better.
Why does it hurt when I Pee ? (Ay Ay Ay https://www.youtube.com/watch?v=w5fLGWrHouk)
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Old 5th February 2005, 01:56 PM   #33
Panelhead is offline Panelhead
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Default Hum Pick up in Le Monstre

I have a strange problem in my Le Monstre. The amp is now where I measure 0.0 mv hum. But this is only without input cabling connected. Once the cable are connected it goes up to 0.2 - 0.3 mv with unterminated shielded short cables. With unshielded it is 0.6 - 0.8 mv ac.
This is with a double shielded power cord. Using an unshielded power cord the measured hum can reach 8 mv depending on cable orientation.
Connecting the preamp to the cables does not help, the measured hum is the same. The preamp has an output transformer with a 38 ohm DCR.
This is the only amp I own that has a problem with hum pickup. The input impedance is around 23K. All my other amps do not have a problem with input cable hum pickup.
On my 100 db efficient speakers the amp is almost dead quiet without cables. I can play with cable dressing and get it lower, but never as quiet as it is without cables.
Laying the cables close to the rear of the amp gives big hum, pickup from power transformer. This is a nice Victoria Magnetics toriod.
Also another goofy question. I have read about the bypassing of the cascode transistors to improve the sound. I tried it in another version, using the PCD Design recommended replacement transistors. It degraded the sound quality.
In this one, original transistors, it has not been tried. Did I do it incorrectly, or is it not needed if the power supply is well built.
One thing learned, this amp can sound great on the right speakers. But it is a devil in exposing power supply issues. Just moving a ground wire connection a couple inches can make the hum go from 0.0 mv to 2 - 3 mv on the outputs.
Anyone thinking of building this amp should be aware. The thing will require some tweaking to get the best out of it. I doubt if anyone has ever built one and had great sonics to begin with.

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Old 5th February 2005, 02:02 PM   #34
gatedriver is offline gatedriver  Europe
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Default Dieter's PCB

Hallo Dieter,

you have lots of free space on that board, you could shift the components much closer together and make a tighter layout on the board. that means you need less board area and get a shorter signal path and less parasitics.
try to avoid sharp corners (smaller than 90 deg), make smooth areas (use polygones in your layout software).

you can probably cut the board are in half..
or more, if you use SMD resistors. 1206 or MELF is really easy to solder, no problem for any DIY.

also, the bypass caps are very close to the input stage and there are none close to the output.

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Old 5th February 2005, 04:24 PM   #35
dieter12 is online now dieter12  Germany
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the board is not so big... Shure, that with the corners is clear, its the first try. No SMD, we would prefer Tantal RsThanks for your commends...

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Old 5th February 2005, 10:36 PM   #36
ericfe1975 is offline ericfe1975  France
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thank you guys!
big thanks to appolon scotw and dieter (in no particular order)
i will now study closer all that information

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Old 23rd March 2005, 12:46 PM   #37
pred is offline pred  Switzerland
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Default output resistance

Hi everybody,

I am also interested in building le Monstre. Before doing that I wanted to look for "European" transistor substitutions and also to do some spice simulations. Although I am electrical engineer I am not, at least in audio, looking for a perfect amplifier.

But what bugs me the most is the simulation of the output impedance. I used the schematics similar to one posted here with Tip3055 tip2955 or replaced them with smaller MJE15030 or D44H11. I always got the output impedance of 2-4 Ohm. That seems a lot to me for the amplifier with the feedback. Do you have any comment on that?

Since we speak of replacements is there any for jfets SJ SK with some 2nxxxxx or similar that is more likely to be found? The same question is for every other?


I was using LTSpice if it is of any significance.
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Old 1st September 2005, 09:59 AM   #38
plovati is offline plovati  Italy
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Regarding to quite high output impedance 2 ohm seems ok, because the monstre exit on collector and was designed to be a 300B solid state equivalent, so with tipical tube damping factor.

Me too prefer to build on ewith current european transistor, but not easy to find replacement for these old toshibe product. High gm input fet that are critical for results seems impossible to find.
Here my list of equivalent (first item of each group is the original one). Any suggestion on equivalent?









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Old 1st September 2005, 11:13 AM   #39
Panelhead is offline Panelhead
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Default Source for parts

www.mcminone.com can supply all the original transistors. I built one using the recommended substitutions listed on the PCB-Design website. Later found the original transistors and built another.
The one built with the original transistors sounded much better. It also was more stable.
One tip I missed. Keep your ground length paths equal from rail to rail and channel to channel. Small differences in the ground paths will increase hum and effect dc offset.
Poor layout and build can cause big problems with stability. It will zing your eardrums.

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Old 3rd December 2007, 01:50 AM   #40
danieljw is offline danieljw  Australia
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Default "Le Monstre" - working

hello people

I just built "Le Monstre" using origional transistors
tried it last night.... I have to say the amplifier sounds really really good
has any one else tried it ???

pictures to come.

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