Help with Schematic.

22nd October 2002, 08:16 PM

Do you think i could add another output pair to this to make it an even 500 watts or will the driver not have enough to power that many?,
Thanks

http://www.mif.pg.gda.pl/homepages/tom/files/400MOS.gif

kevin gilmore · 22nd October 2002, 09:26 PM

This really depends on how much the power supply sags at
500 watts. But there is plenty of drive for another pair
of output fets.

P.Lacombe · 22nd October 2002, 10:07 PM

Mos transistors exhibit a purely capacitive input impedance at audio frequencies, and you can add more devices at the output in order to increase the intensity. But you have to increase the supply voltage too (carefully...)

The only problem is possible increase of distortion at the very high audio frequencies. You can cure this by increasing the current in the driver stage (which is low in my opinion) by decreasing the value of R15 (100, or 82 ohms) . The ordinary effect of this kind of tweak is better clarity, more velocity. It's important to install each pair of MJExxx on a little heat sink to avoid overheating, and some thermal distortion.

Regards, Pierre Lacombe

23rd October 2002, 04:56 AM

thanks,i'm still learning amp design and everytime you guys temm me something like increasing the current thingy i remeber it and learn more

Andypairo · 23rd October 2002, 04:00 PM

You should ask the Saint (Anthony Holton), since he's the designer.

I've built a couple of these with IRFs and they work fine (even if I still only tested them at lower supply voltages, only 55+55V).
Now I'm gonna fire'em up with 70+70V.

Cheers

Andypairo

22nd October 2002, 08:16 PM	#1
CryingDragon Guest	Help with Schematic. Do you think i could add another output pair to this to make it an even 500 watts or will the driver not have enough to power that many?, Thanks http://www.mif.pg.gda.pl/homepages/tom/files/400MOS.gif

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22nd October 2002, 09:26 PM	#2
kevin gilmore diyAudio Member Join Date: May 2002 Location: wheeling illinois	This really depends on how much the power supply sags at 500 watts. But there is plenty of drive for another pair of output fets.

22nd October 2002, 10:07 PM	#3
P.Lacombe diyAudio Member Join Date: Jul 2001 Location: Orleans, France	Mos transistors exhibit a purely capacitive input impedance at audio frequencies, and you can add more devices at the output in order to increase the intensity. But you have to increase the supply voltage too (carefully...) The only problem is possible increase of distortion at the very high audio frequencies. You can cure this by increasing the current in the driver stage (which is low in my opinion) by decreasing the value of R15 (100, or 82 ohms) . The ordinary effect of this kind of tweak is better clarity, more velocity. It's important to install each pair of MJExxx on a little heat sink to avoid overheating, and some thermal distortion. Regards, Pierre Lacombe

23rd October 2002, 04:56 AM	#4
CryingDragon Guest	thanks,i'm still learning amp design and everytime you guys temm me something like increasing the current thingy i remeber it and learn more

23rd October 2002, 04:00 PM	#5
Andypairo diyAudio Member Join Date: Sep 2002 Location: near Milano , Italy	You should ask the Saint (Anthony Holton), since he's the designer. I've built a couple of these with IRFs and they work fine (even if I still only tested them at lower supply voltages, only 55+55V). Now I'm gonna fire'em up with 70+70V. Cheers Andypairo