F5 power amplifier - Page 110

Manu · 8th June 2008, 05:48 PM

jackinnj · 8th June 2008, 06:59 PM

Here's my latest version -- with compensation on the input (150pF), a place for the resistors to adjust the resistors on the source of one MOSFET and one JFET. I use TO-220's for the feedback resistor as I have plenty in stock:

Nelson Pass · 8th June 2008, 07:15 PM

I'm going to suggest that if you want to allow trim on the Source
of a MOSFET and JFET that you allow for both sets, since the need for
trim tends to be random in polarity.

Looneytunes · 9th June 2008, 03:11 AM

Quote:

Originally posted by EUVL
If you have a low impedance speaker, you need more current rather than voltage. You can of course start paralleling matched output devices (e.g. using 2 pairs of MOSFETs will give maximum power at 4 ohm). But paralleling MOSFETs will change the frequency dependent characteristics of the amplifier.

Patrick

Practically speaking, does that mean that the circuit would have to be completely reoptimized to add another pair of MOSFETS?

Looneytunes

Nelson Pass · 9th June 2008, 03:42 AM

Optimization is individual, even within a given design.

You can simply parallel output devices and it will work fine, but
if you tweak some of the resistor values, you can get the most out
of it. This is also true of the published circuit. Most examples meet
a .002% spec at 1 watt, but some run a little higher, and you can
tweak them down. Similarly with the bandwidth.

So if you have a scope and a distortion analyzer, you can always get
a little better.

Looneytunes · 9th June 2008, 04:33 AM

Thanks Nelson.

And thank you for sharing your designs and knowledge with Newbies like me. I'm building this, and I'm sure that I'm going to learn A LOT!

Wynn

sandstorm33 · 9th June 2008, 08:47 PM

Quote:

Originally posted by bogdan_borko
BTW I`d like to hear what mr.PAss thinks of this PCB design of mine?

Thanks in advance.
CHeers.
Borko.

And THANK YOU for your kind generosity. As CHairman of the ETOOTL WORLD CAUCUS (EITHER TO OLD OR TO LAZY) I can tell you that ASSUMPTION to your particular Paradise is secure.

bogdan_borko · 9th June 2008, 09:39 PM

Quote:

Originally posted by sandstorm33

And THANK YOU for your kind generosity. As CHairman of the ETOOTL WORLD CAUCUS (EITHER TO OLD OR TO LAZY) I can tell you that ASSUMPTION to your particular Paradise is secure.

bongo99 · 9th June 2008, 11:03 PM

Any PCB group buy for F5 yet?

Love to build one.

sandstorm33 · 9th June 2008, 11:57 PM

Quote:

Originally posted by bongo99
Any PCB group buy for F5 yet?

Love to build one.

Betcha it happens!!!

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8th June 2008, 05:48 PM	#1091
Manu diyAudio Member Join Date: Nov 2002 Location: Vienna, Ostrich

8th June 2008, 06:59 PM	#1092
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	Here's my latest version -- with compensation on the input (150pF), a place for the resistors to adjust the resistors on the source of one MOSFET and one JFET. I use TO-220's for the feedback resistor as I have plenty in stock:

8th June 2008, 07:15 PM	#1093
Nelson Pass The one and only Join Date: Mar 2001	I'm going to suggest that if you want to allow trim on the Source of a MOSFET and JFET that you allow for both sets, since the need for trim tends to be random in polarity.

9th June 2008, 03:42 AM	#1095
Nelson Pass The one and only Join Date: Mar 2001	Optimization is individual, even within a given design. You can simply parallel output devices and it will work fine, but if you tweak some of the resistor values, you can get the most out of it. This is also true of the published circuit. Most examples meet a .002% spec at 1 watt, but some run a little higher, and you can tweak them down. Similarly with the bandwidth. So if you have a scope and a distortion analyzer, you can always get a little better.

9th June 2008, 04:33 AM	#1096
Looneytunes diyAudio Member Join Date: Oct 2005	Thanks Nelson. And thank you for sharing your designs and knowledge with Newbies like me. I'm building this, and I'm sure that I'm going to learn A LOT! Wynn

9th June 2008, 11:03 PM	#1099
bongo99 diyAudio Member Join Date: Jun 2004 Location: Bayarea, CA	Any PCB group buy for F5 yet? Love to build one.

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