New amp design

[jleaman]

Well here it is i finaly got is and scanned it. it is my dads layout and design but here it is have a look any sujestions are welcome.. it is a fet design and produces about 75watts class ab

J'

 

[The Saint]

Hi Jason

I looks alot like IRF's application note ampifier schematic.


Regards

Anthony

 

[jleaman]

yes yes it is verry close but has been changed alittle.. new board layout and ect ect components have been changed. too..

 

[jleaman]

can any one sujest some input or upgrades..

J

 

[The Saint]

I would add 220 Ohm Gate resistors and 0.22 Ohm 5 watt Source resistors and replace the IRF100 devices for IRFP240's or something similiar.

Regards

Anthony

 

[jleaman]

well curently there are irf 540's in there you stuill sujest irfp240's i have a whole pile of them too.. from my n-channel amp..

HEHE

Hey anthony do you still have any n-channelboards instock..?

J'

 

[The Saint]

Yep, I still a few left in stock.

Anthony

 

[jleaman]

so i should use irfp240's in this sircuit..?

 

[The Saint]

You can if you wish , they should work fine...

Anthony

 

[jleaman]

will i have to change any parts in the schematic or just leave it and put the irfp240's in and re bias it..
do i change the input voltage or keep it at 42 volts and what do you think that my power out will be.. im not looking for lots but just ceriousse.

J

 

[The Saint]

Just drop them in place and re-bias.

42 volt rails should yield you about 80 to 90 watts into 8 Ohms. with the right transformer. If you stick to about a 200va transformer.

Anthony

 

[leo529]

the second stage can change to current sourse....

 

[Nelson Pass]

This schematic appears to be the Mosfet Citation 12,
as seen on page 9 of Audio Amateur 2/1981.

You can see it along with the article at www.passdiy.com

 

[jleaman]

here we go..

 

[jleaman]

and another.

 

[jleaman]

and another hehe

 

[jleaman]

yeahh looking good..

 

[topicreader]

Hi!
Here is a FET amplifier that appeared in a DIY magazine. Its work perfect, the first and second stage are stabilized and the sound is very good. I know to advise.
Isaw your amplifier pictures and I think the long wires with MOSTFETS is bad idea. Mosfets has big input capacity and your amplifier will maybe to generate.I think would be better if you would to build the FETS on the PCB.The DIY magazine also built directly on the PCB the FETS.
Good Luck!

 

[jleaman]

actualy im going to make the wires smaller ( less longer) and use that.. ill have to power it up via variac this weekend.. see how she works then ill put the othere channel togethere and make them a stereo set im thinking about make ing small mono blocks and then building the e-holton hitachi lateral amps after that way i have some thing to do..

J'

 

[The Saint]

Actually it's not the length that's important. But the cross sectional area which is. Its just the lead inductance which causes the instablity and you reduce that by using thick wire.
However there is a point of deminishing return, where length does come into play and causes instablity.

Cheers

Anthony E Holton
aussieamplifiers.com