Hiraga "Le Monstre"

well it will be an very interesting experiment and very instructive to see how it sounds after the rework.
what if no difference is noticeable?
then we will have a bipolar monster, a crazy one that can be built by lots of passionate ...a great legacy!!

i will keep on trying any help is apreciated.
 
The one and only
Joined 2001
Paid Member
ericfe1975 said:
well jfets easily picks up rf , bipolars dont do it as easily.

In my experience the opposite is true. I have never had a FET amplifier
give me trouble with RF.

Le Monstre is a classic design, and there are several contemporary
pieces which are homages to it whether the designer knows it
or not.

I do think, however, that device technology has improved enough in
the last 26 years that it can be made better.

:cool:
 
Thanks for your information Mr Pass ; as jfets has an extremely low input impedance comparated to bipolars I was sure that it would means more sensitivity to RF .
I can remember days in my youth when i was playing with jfet devices picking up AM rf noise an thus having a very simple radio :) .

I also have heard extremely good things about Mr Pass amps that are built around FET devices.

I think that good job can be done with the monster, usually good job starts with some experimentation.
Maybe it is not such a good idea to replace the jfet with a compound bipolar device, maybe it is...trying it is the only way to know.

In your personal opinion, Mr Pass how could the "le monstre" took some advantages of the new hardware and philosophy developped nowadays?

Maybe it is time for the "le Monstre " to have a son or a bride, just like the Zen did ;).
 
Try to think RF interference as bad shielding and not as component thing. To minimize RF interference in audio:

1. Use thick aluminum chassis all the way around the box of the amplifier (the best way to minimize RF).
2. At the input, Use a ferite ring and wind 1-2 windings of the same coaxial cable that comes from your RCA to the input of the amplifier.
3. Use coaxial cables and connectors. Coaxial cables for low level signal. I use coaxial cables in my new monster for the speakers too. Have you thought that unshielded speaker cables can pick RF? They can. If possible get rid of the "must" philosophy of many companies. Use RF coaxials and plugs. Low capacitance RF cabling is much better and has much stronger shields than many high quality audio cables. And since impedance in audio cables is not of too much importance, one should give priority to shielding and low capacitance of the cables.
4. If you can, try to think a way to power the monstre from batteries. This is a more extreme approach that I am thinking, but in such low voltage amplifiers it is feasible. Power supplies may pick RF interference from the high voltage network.

Finally think that you will get much more RF interference from your phono cartridge or your passive preamplifier if you have one, so shielding is of much importance there.
 
ericfe1975 said:
... as jfets has an extremely low input impedance comparated to bipolars...

Please can you explain how did you come to this conclusion ?
One of the main reasons to use jfet in some audio circuits is its almost infinite input impedance.
Friendly advice: read the k170/j74 datasheets, read the jfet articles on Borbely's site, it seems that you lack a basic knowledge on this matter.
Best regards!
 
Excuse me!!! you are totally right, i said exactly the opposite i had in mind: fets are voltage controled devices , so almost no curent is needed wich means an extremely HIGH impedance and thus an extremely low current level signal can have a noticeable effects.
i mixed those ideas in a very bad way.

In fact RF interference depends also of the components : a bc560 with an Ft or more than 200 Mhz, and a high gain is more likely going to pick up RF than a 2n3055 with an Ft of 0,8Mhz and much lower gain.

Jfet are comonly fast devices with an extremely HIGH input impedance , exactly what you need to pick up RF .
 
Yes, the human minds have the tendency to wonder off sporadically :D
I see that you had in mind to replace input JFETs in LeMonstre with BJTs. One way to do it would be:
 

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ericfe1975 said:
thanks a lot for the schematic! in fact i had in mind to replace the fets by a bc5xx in darlington.

Why would you need a darlington here?



ericfe1975 said:
the bf245 is a FET :( the idea was a monstre with no FET at all ...

BF245C acts here as a constant current source (CCS) - you can use any 6mA CCS or just use 1K8-2K2 resistor instead of CCS
 
lumba please explain which idea confuses you , i am sure we can help you.
Yes i have noticed that a monster without jfet is like a "la classe classe A hiraga " :) .

Well as Mr pass said, after all those years of progress for sure the monster can take some benefits.
the point is not "improving" the monster, here the point is trying a le monstre without jfet and hear it.

I do not belive that someone serious may have the arrogance to say " you know what? i am going to improve one of the best design in a class audio simply removing the fets"

and certainly this is not my case. I am not saying either that jfet sound bad. not at all!!! every jfeted amp i've heard sound very clear and warm.

thx for the schematic, i just got a good one in my own work, fully implemented thanks to the clarty of my ideas ( ;) lumba )

see you later.
 
Member
Joined 2005
Paid Member
darian said:
Hello,

Actually, if you want to make a Le monstre without fets, it's basically becoming a Hiraga 20w, all bipolar :
http://www.tcaas.btinternet.co.uk/hiraga2.htm

and here on diyaudio:
http://www.diyaudio.com/forums/show...&perpage=25&highlight=hiraga+20w&pagenumber=1

But the sound is believed to be different, more precise but less transparent from Hiraga himself opinion.

But once again, nothing wrong with fets and you get a nice quadratic curve from them, not a nasty exponential!

Regards


Having built and listened to both amplifiers i would agree with this comment. both amplfiers are excellent.

-Dan
 
Dear all,
I am thinking of powering this 8W amplifier using batteries only, and recharge them after use. I need to ask a few things in order to avoid spending extra money on this.

1. What is the current consumption of the amplifier? (each channel)

2. Can I connect two identical batteries in series in order to take +12V, GND, -12V ? (just to make sure)

3. I have two 80AH 12V deep cycle lead acid batteries. About how much the operation time will be?

4. Can I use just two batteries for both channels? (the same psu for both channels)

5. Finally, can I leave the batteries stand alone to power the amplifier or do I need to connect capacitors parallel to them? And what could be the effect in sound when using no capacitors at all? (not so fast responce, etc)


I yould appreciate a helpful answer in these five points which will save me extra cost.

Best regards