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Old 31st October 2014, 03:58 PM   #1
Fred974 is offline Fred974  Reunion
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Default Class A 8W

Hy there.

I show you my new build. A single end class A based on irfp240.

Some pics of the build.

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Fred.
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Old 31st October 2014, 04:10 PM   #2
kevinkr is offline kevinkr  United States
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Nice looking project, do you have schematics you could share with the membership?
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Old 31st October 2014, 05:06 PM   #3
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An electrolytic cooker, nice.
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Old 31st October 2014, 05:29 PM   #4
kevinkr is offline kevinkr  United States
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Might want to place a small gate stopper resistor in series right at the gate lead of your IRFP240 to prevent oscillation.
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Old 31st October 2014, 06:24 PM   #5
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by Fred974 View Post
Hy there.

I show you my new build. A single end class A based on irfp240.
Hi Fred - welcome to the forum !!!!

You come from a cool island I've never been to, fantastic to see somebody on the forum from exotic locations

Please tell us more about your project - circuit diagram, sound, what speakers do you use with it etc. ?
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Old 31st October 2014, 06:49 PM   #6
Fred974 is offline Fred974  Reunion
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Nice looking project, do you have schematics you could share with the membership?
Thanks.

here is the diagram. a single ended mosfet driven by a constant current generator.

Rg not 4.7k but 220ohms.
And mosfet all irfp240.
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Old 31st October 2014, 06:56 PM   #7
Fred974 is offline Fred974  Reunion
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Might want to place a small gate stopper resistor in series right at the gate lead of your IRFP240 to prevent oscillation.
Hy.

For the resistor what value do you think i CAN place. Prevention is better than cure.

cards have already been tested. and they work very well. no oscillations. I think.

Fred.
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Old 31st October 2014, 07:11 PM   #8
Fred974 is offline Fred974  Reunion
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Originally Posted by Bigun View Post
Hi Fred - welcome to the forum !!!!

You come from a cool island I've never been to, fantastic to see somebody on the forum from exotic locations

Please tell us more about your project - circuit diagram, sound, what speakers do you use with it etc. ?
Thanks.

My project.

I start from zero. the goal is to reconstruct me a system open baffle multi amplified 3-way driven by class A amp.
For the speakers, i use actually my diy ob with electrovoice parts and a
high band range speaker. It´s not finish but the sound in very good for me.
I would like to add in the future two eminence alpha 15.

Sorry for my english.
Fred.
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Old 31st October 2014, 08:16 PM   #9
Bigun is offline Bigun  Canada
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That's quite an ambitious project - and a lot of fun. Don't forget to consider dc speaker protection (a module from eBay maybe).

The power supply is also very important, do you have any issues with mains hum in the sound ?
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Old 1st November 2014, 12:13 AM   #10
GoatGuy is offline GoatGuy  United States
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Good Work there, Fred.

One thing … While having the MOSFETs connected the way you do is fine, my own inclination would be to experiment with having the output tied back to the inverting input, to close the gain loop from source all the way to the tail. yes, as others will likely chime in quickly, there "are things to consider". But just about all distortion that might come from the MOSFET tail could be reduced to negligible levels.

also - It is kind of late in the design to suggest this, but having the big capacitors above your heat sinks is asking to cook them big-time. Not wise. It would be better to position them just the opposite. Move the heat sink to the top, and put the electrolytics on the bottom.

8 Watts only? I think you're going to get closer to 20 watts.

But what do I know.

GoatGuy
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