F5 power amplifier

[Nelson Pass]

If you use 2 of them per channel.

[moe29]

heatsink rule of thumb... take what you think is good enough, then double it.

or use fans.

[KSTR]

Originally posted by EUVL
I have not managed to figure out why you [TimS in his last proposal] need diodes between the JFET gates ??

To get the front end bias back up while keeping the 100R's in the sources, it looks like. Probably not the most elegant solution (wrt impedance, PSRR).

- Klaus

[Dougie085]

So I'd be better off just getting 2 12" long ones? They do .375 c/w. With just 2 fets be hard to put them on 2 different heatsinks I would think. Unless I didn't mount them on the PCB but wouldn't that take away from the sound quality? I've heard some people say they should be on as short of leads as possible.

[Dennis Hui]

My copy of AX has arrived!

Thank you so much, Mr. Pass. (And I wish you
a speedy recovery.)

Dennis

[Nelson Pass]

Originally posted by Dougie085
So I'd be better off just getting 2 12" long ones? They do .375 c/w. With just 2 fets be hard to put them on 2 different heatsinks I would think. Unless I didn't mount them on the PCB but wouldn't that take away from the sound quality? I've heard some people say they should be on as short of leads as possible.

No problem. I would just run a few inches of wire either way.

[Dougie085]

Ok well I have 6 of those 6" heatsinks so I could use 2 per monoblock. I'm trying to figure out the easiest way for me to make some PCB's. I found a place that will let you do 3 small boards for like 51 bucks + shipping. Anyone know a better deal? I saw the printer mod for the epson and it looks nice but I think I'd spend more then 51 bucks on that and not sure I'd use it often enough to have a dedicated printer for printing PCB's. Also saw the iron on method with a laser printer but again I'd have to buy a laser printer.

[Nelson Pass]

Originally posted by Dougie085
Ok well I have 6 of those 6" heatsinks so I could use 2 per monoblock. I'm trying to figure out the easiest way for me to make some PCB's. I found a place that will let you do 3 small boards for like 51 bucks + shipping. Anyone know a better deal? I saw the printer mod for the epson and it looks nice but I think I'd spend more then 51 bucks on that and not sure I'd use it often enough to have a dedicated printer for printing PCB's. Also saw the iron on method with a laser printer but again I'd have to buy a laser printer.

If you toss the current limiting and temp compensation, there's barely
enough to justify a board. Get some prototype board at Radio Shack.

[Dougie085]

Ok I could probably do that. Is there going to be a version for balanced inputs?

[defect9]

Originally posted by apassgear
Here is one way we could lay a one sided board for the F5 circuit based directly on Nelson’s schematic.

Still on the proofing stage so suggestions, discussion and corrections are welcomed.

Needing components to attach the blue LED that will be added soon so no nasty for this omission please.

Nelson, thanks for sharing this wonderful amp that I’m sure will transcend time and be regarded as a classic.

hmmm... I like it. really simple. curious if the FETs are going to be too close together on the heatsink. maybe swing them out to be on opposite sides of the boards, and make the board a little longer to give them another inch or so. Just my thoughts. Beautiful nonetheless!

Definitely hoping a group buy happens with the final layout, whatever it happens to be.

-Jared