Le Monstre Fet connection!

Status
Not open for further replies.
Jump to Latest
Audiofanatic

Audiofanatic

Member
Joined 2002
audio-finesse.com
#1
Hi Monstre DIYers,

I want to build two Le Monstre Monoblock's but don't know how to connect the Fet's at the input.
Are the drains connected to the 100 ohm pot or the source?
Or the source from the upper and the Drain of the lower fet or the other way around?

Thanks in advance!

Audiofanatic 😉

P.S. look at the arrows and the dots!
 

Attachments

  • monster fet.jpg
    monster fet.jpg
    29.5 KB · Views: 1,534
#4
J-fets

2SK170 Fet's drain connect to 1K at + power supply, 2SJ drain to 1K at - power supply.

2sk170 - n channel j-fet. In "normal" mode ( called saturation ) drain is positive respect to gate, and gate is negative respect to source.

Or, drain is positive respect to gate, source is positive respect to gate but less than drain is. Result drain is positive respect to source.


2sj74 p-channel drain is negative vs gate, source is negative vs gate, drain is negative vs source.
 
#9
Hi DIYers,

Thank you very much for your help.
I didn't expect so much reaction on this thread.
I'm realy thankfull to you all! I'll report a.s.a.p. to you guys when my two Le Monstre's are ready.

To Frank, ik vind het heel attent van je dat je bereid bent/was mij hiermee te helpen. Dankje wel!

Frendly greetings,

Audiofanatic 😉:idea:

P.S. If I succeed in making new PCB's I'll post it eventually on this thread.
 
#10
Re: Long live Silicon!

Hi,

Hi Jam,

Long live Silicon Valley?:goodbad:

Trolling? Qui? Moi?

You know that when I see something like Kaneda, Le Monstre or Hiraga I just have to subscribe to the thread...if only to prevent you guys from making mistakes. :clown:

Hi Audiofanatic,

To Frank, ik vind het heel attent van je dat je bereid bent/was mij hiermee te helpen. Dankje wel!
Click to expand...

Thank you, I actually didn't do anything...yet.😉
 
#12
millwood said:
has anyone tried to replace the output devices with a mosfet? IRF for example?
Click to expand...


Why would you do somthing like that? Start with Fet's and end with fet's. IMHO (Output) Fet's sound HARD, COLD and To my ears fatigue is near by. :bawling: :bawling: :yell:

I don't mind Fet's in the input of an amp, but to start and finish with fet's is asking for trouble. If you don't agree, it's fine by me but that's my experience.

Regadrs,

Audiofanatic 😉
 
#13
I remember some amp design called the "Mosquito" that might answer your question. Try a google search or even a search on this forum somewhere. Hitachi (or similar Lateral process) devices as opposed to the IR HEXFET thingies.

mlloyd1

millwood said:
has anyone tried to replace the output devices with a mosfet? IRF for example?
Click to expand...
 
#15
millwood said:
thanks, Mollyd1, for the tip.

I found this:

http://perso.wanadoo.fr/jm.plantefeve/sche.html

Pretty interesting.

Yes, Audiofanatic, I also think fet in and fet out are hard, cold and fatique-inducing. That's why the PASS SE amps are so un-POPULAR, 🙂
Click to expand...


I was not clear in my last post.

Fet in and Fet out sound great, but not on my ESL's they sound good on dynamic loudspeakers, and maybe om ribbon tweeters but not om electrostatic loudspeakers, and that's what I love most. Because they are so great in puting a holographic sound stage infront of me; and behind me.

Regards,

Audiofanatic 😉
 
#17
What does it achieve?

This is to make sure that the same voltage drop is seen across each of the 68 ohm resistors to avoid excessive power dissipation across one. :flame: This is so you can use 1/4 resistors for each 68 ohm. If you use 1 watt 68 ohm resistors you can eliminate the 10 K for greater high frequency linearity. If you are going to leave the 10 K resistance in the circuit, use two 20 K one watts with the one end of each returned to the power supply voltages (one negative and one positive) They will look to be in parallel and like 10 K to AC signal voltages. This will improve the PSRR by 12 dB without any penalties except the very modest cost increase for the extra resistor. The 68 ohms can remain 1/4 watts for this approach as well.:treasure:
 
#18
It lowers the open-loop gain to a more controllable value. The VAS has a current output but the mosfets have a voltage input. Without the resistor the only thing that limits the DC gain is the Early-effect (collector current changes a bit with voltage) of the VAS transistors.
 
#19
megajocke said:
It lowers the open-loop gain to a more controllable value. The VAS has a current output but the mosfets have a voltage input. Without the resistor the only thing that limits the DC gain is the Early-effect (collector current changes a bit with voltage) of the VAS transistors.
Click to expand...

I am not sure how to calculate the open-loop gain on the VAS here (I don't even know how to calculate the bias here, given that we are dealing with th jfet).

so I am not sure how high the gain is here.

A simple question.

What about bootstrapping the two VAS transistors, like in the MOSFET Citation 12? For example, replacing the 10K transistor with a capacitor and put the other end of the capacitor on the output terminal. You will still maintain the DC characteristics of the existing circuitry but the AC gain will increase considerably.

Will this work?
 
Status
Not open for further replies.
Top Bottom