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Old 19th October 2015, 12:41 AM   #1
wdecho is offline wdecho  United States
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Default Schade circuit using IRFP240's

What if we do not need an amplifier with 50 watts of power but are satisfied with the 25 or so watts most Firstwatt designs have. What would have to be changed in the circuit to use the very common IRFP240 mosfet in the new circuit with the schade feedback and or would it have the SET curves? I am just a solder slinger and not a designer nor do I have or use the software to design circuits. I wonder if this is the circuit in the new F7 Nelson was talking about in the 6Moons article. I do like SE circuits over PP.
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Old 19th October 2015, 06:54 AM   #2
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Just lower PSU voltage and bias current to about 40V and 2A.
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Old 19th October 2015, 03:19 PM   #3
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if you search for original post (Papa mentioned , but I also forgot who originally contributed that**) with IRFP240 Shade recipe , you'll see that resistor values are 1K signal to gate , 10K drain to gate

no other gate (stopper) resistors

just be careful with biasing

** found it - revintage is one to blame for that useful trick to sand parts

Click the image to open in full size.
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Old 19th October 2015, 03:46 PM   #4
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This thread will surely assist you with something to build

If You Don't Have a SIT, Fake It...
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Old 19th October 2015, 04:59 PM   #5
wdecho is offline wdecho  United States
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Quote:
Originally Posted by Zen Mod View Post
if you search for original post (Papa mentioned , but I also forgot who originally contributed that**) with IRFP240 Shade recipe , you'll see that resistor values are 1K signal to gate , 10K drain to gate

no other gate (stopper) resistors

just be careful with biasing

** found it - revintage is one to blame for that useful trick to sand parts

Click the image to open in full size.
Thanks Zen, I assume there is nothing wrong with having the mu follower with a IRFP240 like Papa did in the video. If I am wrong correct me.
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Old 19th October 2015, 05:00 PM   #6
wdecho is offline wdecho  United States
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Quote:
Originally Posted by 2 picoDumbs View Post
This thread will surely assist you with something to build

If You Don't Have a SIT, Fake It...
This is all new to me, thanks.
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Old 19th October 2015, 05:04 PM   #7
Zen Mod is offline Zen Mod  Serbia
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for IRFP240 mu-recipe , look no further than ACA
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Old 19th October 2015, 05:11 PM   #8
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With schade feedback we have now different curves, ok. But what does it mean for the real performance? Lower distortion? Or different THD spectra? Do we also have lower gain with schade?
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Old 19th October 2015, 05:16 PM   #9
wdecho is offline wdecho  United States
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I am lucky to have some of the V-Fets and actually have a board for one of the earlier designs but I am waiting for the SE design Papa has promised. This Schade circuitry just peaked my curiosity and it would be a great project to build and see how it performs. Maybe one day. Then maybe someone else that does not have the V-fets will jump in the water.

A SIT sounding amplifier using common available mosfets, what's there not to like.

Last edited by wdecho; 19th October 2015 at 05:25 PM.
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Old 19th October 2015, 07:00 PM   #10
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by kacernator View Post
With schade feedback we have now different curves, ok. But what does it mean for the real performance? Lower distortion? Or different THD spectra? Do we also have lower gain with schade?
nothing wrong in observing Papa's BAF lecture again
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