I used the new schematic with some modifacations. It is biased higher than normal. The rail voltages are 14.8 volts. The power supply is a C-R-C 22000 uf, .2 ohm, 22000 uf. The outputs are mjw1302,3281. It has a very nice sound, more bass than I expected. I am swithing between the Mini-A, JLH, and Le Monstre. Each has a little different sound.
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sound
The bias of all amps is approx. 3 amps. The JLH and Le Monstre have 15 volt rails and the Mini-A is 18.
I have only been listening to thr JLH for a week. It is getting the Sponge Bob Square Pants test as I write this. Each amp I build or rebuild gets to go in the living room for a week or two to get feedback. The Mini-A sounded great just a little to wide to fit properly. Le Monstre fit perfect. It had more bass but not quite enough highs. I think it needs a few more tweaks.
I am going to build another JLH. I have a couple of extra boards if anybody wants them. I did screw up one Transistor footprint. The leads for Q8 need to be switched to fit in a BD140 or Equivlant. I used MPSW51's and turned down the bias to 3 amps.
More in a week.
The bias of all amps is approx. 3 amps. The JLH and Le Monstre have 15 volt rails and the Mini-A is 18.
I have only been listening to thr JLH for a week. It is getting the Sponge Bob Square Pants test as I write this. Each amp I build or rebuild gets to go in the living room for a week or two to get feedback. The Mini-A sounded great just a little to wide to fit properly. Le Monstre fit perfect. It had more bass but not quite enough highs. I think it needs a few more tweaks.
I am going to build another JLH. I have a couple of extra boards if anybody wants them. I did screw up one Transistor footprint. The leads for Q8 need to be switched to fit in a BD140 or Equivlant. I used MPSW51's and turned down the bias to 3 amps.
More in a week.
Problem with highs
Hello Mike,
what speakers do you use on the Monstre?
I'm using ESLs and also have problems with the high frequencies.
See: http://diyvideo.com/forums/showthread.php?s=&threadid=29233&highlight=
The impedance correction helped somewhat, but I haven't yet had the time to further look into the problem.
Did you check the amp for oscillation? In one of the original articles putting a small cap in parallel with the 220 resistor is mentioned as a possible solution.
Also, I'd like to know what made you decide to use less than 100000uF in the PS. From others I understand that increasing the capacitance in the PS benefits the sound substantially.
Johan
PS. I'm interested in the JLH boards if you still have them
Hello Mike,
what speakers do you use on the Monstre?
I'm using ESLs and also have problems with the high frequencies.
See: http://diyvideo.com/forums/showthread.php?s=&threadid=29233&highlight=
The impedance correction helped somewhat, but I haven't yet had the time to further look into the problem.
Did you check the amp for oscillation? In one of the original articles putting a small cap in parallel with the 220 resistor is mentioned as a possible solution.
Also, I'd like to know what made you decide to use less than 100000uF in the PS. From others I understand that increasing the capacitance in the PS benefits the sound substantially.
Johan
PS. I'm interested in the JLH boards if you still have them
idle current
The idle current of your Monstre seems outrageous to me. The original article recommends an idle current of about 600 mA giving slightly less than 8 Watts of classe-A power @ 8 Ohms.
Why making this 3 Amps? Given the voltage rails of 14 Volts there is no way the amp benefits from this high current unless you use speakers that show very low impedance (but is the Monstre suited to these kind of speakers? I think not). The original transistors would collapse using 3 Amps.
Furthermore I am interested in your tweaking efforts resulting in more highs and more sparkling sound. I see the same thing in my experimental Monstre: it is a very special and relaxing sound with a lot of finesse but is misses some sparkling highs (that the JLH does have by the way).
The idle current of your Monstre seems outrageous to me. The original article recommends an idle current of about 600 mA giving slightly less than 8 Watts of classe-A power @ 8 Ohms.
Why making this 3 Amps? Given the voltage rails of 14 Volts there is no way the amp benefits from this high current unless you use speakers that show very low impedance (but is the Monstre suited to these kind of speakers? I think not). The original transistors would collapse using 3 Amps.
Furthermore I am interested in your tweaking efforts resulting in more highs and more sparkling sound. I see the same thing in my experimental Monstre: it is a very special and relaxing sound with a lot of finesse but is misses some sparkling highs (that the JLH does have by the way).
Hi, Maybe your output transistors are too slow. Anyway these are not the ones recommended by Kaneda. This may have the effect of the dog chasing its own tail. See f.a. Application Note # 47 at www.linear.com (High Speed Amplifier Techniques)
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