F5 power amplifier - Page 460

jackinnj · 25th July 2009, 12:41 PM

Quote:

Originally posted by bobodioulasso

This does not seem to be the case here

http://www.6moons.com/audioreviews/firstwatt7/f5_2.html

I will stick to my story. The gate resistor on the MOSFET should be as close as possible to the output device. I can get my F5's to operate into the MHz without problems (yeah, I know that's an abusrdity).

ma_coule · 25th July 2009, 12:49 PM

Quote:

Originally posted by jackinnj

I can get my F5's to operate into the MHz without problems (yeah, I know that's an abusrdity).

No, it's not - since you try to check & proof the stability of your amp!

Cheers,

bobodioulasso · 25th July 2009, 01:07 PM

Quote:

Originally posted by jackinnj
...The gate resistor on the MOSFET should be as close as possible to the output device...

I totally agree with you but you spoke also about the distance from JFets to this resistor, which doesn't look so important to me.
Though i may be wrong as i did not experiment with this.

jackinnj · 25th July 2009, 01:17 PM

I have a run of 0.300 inch (7.6mm) from gate-stopper to mosfet. The F5 layout shown on 6-moons spreads the MOSFET's heat better. Still I have 4 of these guys running -- from mounting hole to mounting hole the spread is 3.800" = 96.5mm and eyeballing the First Watt amp it would appear to be 2x this at least.

sangram · 25th July 2009, 01:36 PM

Jack, what about the other end? I can probably get within a few millimeters myself on the gate side, but will be difficult on the drain of Q1. There are at least 4 solder connections to be made on that 'track', and this will make it really tough to get better than 15mm or so, maybe a bit more.

npapp · 25th July 2009, 03:09 PM

I can definitely get shorter traces from the jfet drain to the g-s resistors if I move the jfet further toward the MOSFETs, but this gives me a much longer input trace from R1 to the jfet source. Should I worry about the input trace length? I was trying to keep it as short as possible.

N

Nelson Pass · 25th July 2009, 03:30 PM

Quote:

Originally posted by npapp
I can definitely get shorter traces from the jfet drain to the g-s resistors if I move the jfet further toward the MOSFETs, but this gives me a much longer input trace from R1 to the jfet source. Should I worry about the input trace length? I was trying to keep it as short as possible.

I wouldn't lose any sleep over it.

Sisyphism · 25th July 2009, 06:53 PM

Could anybody anwer my question from post 4857 ?

This is my first try, single channel layout.

Any comments?

bobodioulasso · 25th July 2009, 07:14 PM

I would try but returning the speakers to psu instead of pcb.
I would insert a serial bulb into the mains for the first run.

Sisyphism · 25th July 2009, 07:15 PM

Post #4587 sorry.

25th July 2009, 07:15 PM	#4600
Sisyphism diyAudio Member Join Date: Jul 2009	oops... wrong Number posted Post #4587 sorry.

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25th July 2009, 01:17 PM	#4594
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	I have a run of 0.300 inch (7.6mm) from gate-stopper to mosfet. The F5 layout shown on 6-moons spreads the MOSFET's heat better. Still I have 4 of these guys running -- from mounting hole to mounting hole the spread is 3.800" = 96.5mm and eyeballing the First Watt amp it would appear to be 2x this at least.

25th July 2009, 01:36 PM	#4595
sangram diyAudio Member Join Date: Sep 2002 Location: India	Jack, what about the other end? I can probably get within a few millimeters myself on the gate side, but will be difficult on the drain of Q1. There are at least 4 solder connections to be made on that 'track', and this will make it really tough to get better than 15mm or so, maybe a bit more.

25th July 2009, 03:09 PM	#4596
npapp diyAudio Member Join Date: Feb 2006 Location: New Jersey	I can definitely get shorter traces from the jfet drain to the g-s resistors if I move the jfet further toward the MOSFETs, but this gives me a much longer input trace from R1 to the jfet source. Should I worry about the input trace length? I was trying to keep it as short as possible. N

25th July 2009, 07:14 PM	#4599
bobodioulasso diyAudio Member Join Date: May 2008	I would try but returning the speakers to psu instead of pcb. I would insert a serial bulb into the mains for the first run.