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Author Topic: 60W MosFet Audio Amplifier  (Read 17940 times)

whosyourdaddy

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60W MosFet Audio Amplifier
« on: August 19, 2009, 09:17:57 AM »
Hello everybody!

I'm kind off hot for building this amp.
What are your opinions on this schematics/design?



So I was wondering if someone have already build it?
My problem is PCB design and any help would be welcome.

TNX

J M Fahey

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Re: 60W MosFet Audio Amplifier
« Reply #1 on: August 19, 2009, 10:52:13 AM »
Hi whosyourdaddy.
I have built something *very* similar, including the "Led bias", and that´s the problem: MosFets are very heat sensitive (because these are the cheap switching type and not the very expensive audio type), and the "bias" arrangement simply doesn´t track heat sink temperature at all, so either it sounds good and self destroys or lives and has *horrible* crossover distortion.
Most "Red circuits" are untested and not very reliable.
I think you´ll be much happier with a tried and true LM3886, and if you are power hungry, bridge a couple of them.
By the way, you´ll easily find PCB designs for them, one of many at GGG, or you can even get ready made boards or kits.
Good luck.

diandsh

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Re: 60W MosFet Audio Amplifier
« Reply #2 on: September 04, 2009, 02:30:49 PM »
I was built this amplifier. Necessarily build it. It is much better lm3886. :tu:
I have received very good impressions. Despite simplicity, a magnificent sound!!!.
If you need PCB layout please write here.

whosyourdaddy

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Re: 60W MosFet Audio Amplifier
« Reply #3 on: September 07, 2009, 06:38:13 AM »
I was built this amplifier. Necessarily build it. It is much better lm3886. :tu:
I have received very good impressions. Despite simplicity, a magnificent sound!!!.
If you need PCB layout please write here.

Yes please that pcb would be great. I will give it a try.

brownstocker

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Re: 60W MosFet Audio Amplifier
« Reply #4 on: October 18, 2009, 12:09:05 PM »
ya if you please me to want that pcb because i built it but didn't work and revised my pcb and nothing changes so please can any one tell me if it's work and i faild or what???

J M Fahey

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Re: 60W MosFet Audio Amplifier
« Reply #5 on: October 18, 2009, 07:27:17 PM »
Hi Brownstock. Can`t talk about what you built , but the schematic as posted works, only the biasing arrangement is poor. If you can live with some crossover distortion, fine.

rowdy_riemer

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Re: 60W MosFet Audio Amplifier
« Reply #6 on: October 19, 2009, 12:43:55 PM »
I noticed that the Red Circuits site specifies Q8 as an IRFP240, which has an absolute maximum gate-source voltage of +-20V. With the source follower set-up, the source voltage will closely follow the gate voltage. Perhaps if the gate voltage rises faster than Q8 can react, there will be a short time when the gate-source voltage exceeds 20V. Maybe a zener diode connecting the source to the gate will fix this. Ditto for Q9. Maybe certain bias adjustments affect the likeliness of this condition occurring. In an extreme case of putting the voltage between the gates at 40V, you would reach the maximum GS voltage. In any case, biasing closer towards class A would reduce the quiescent GS voltage.

Perhaps it would be safer to bias more towards class A if we added one or two parallel sets of MOSFETs and reduced the current through each set by increasing R14 and R15. If this all sounds like nonsense, then maybe I need to drink some more coffee.  :)

diandsh

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Re: 60W MosFet Audio Amplifier
« Reply #7 on: December 23, 2009, 03:48:54 PM »
Sorry for long time... Here is pcb.

askwho69

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Re: 60W MosFet Audio Amplifier
« Reply #8 on: July 23, 2011, 02:48:59 AM »
Sorry for long time... Here is pcb.

hello sorry for raising this up! by the way the zip is corrupted :(

J M Fahey

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Re: 60W MosFet Audio Amplifier
« Reply #9 on: July 23, 2011, 12:07:28 PM »
Too late !!! :'(
Diandash hasn't been here since 2009 !!
Anyway, if you get into his profile, get his mail and write a polite letter, he might re-post.
Good luck.

askwho69

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Re: 60W MosFet Audio Amplifier
« Reply #10 on: August 04, 2011, 11:15:33 PM »
Thank you sir :D