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Old 21st April 2012, 11:39 PM   #1
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Default "crippled" f4 max psu voltage

hi all
i have gathered the parts for a f4 build using auto formers for my frontend and am going to be removing the jfets at the input (crippled as they say)

can i use a higher rail voltage now that the jfets are removed ?
i ask as i already have 2 potted 500va 25/0/25 toroids i,d like to use rather than buy new 18/0/18 toroids

i will also only be using 1x irfp240 /irfp9240 per channel instead of the 3x used with the normal f4 and would like to know if this is safe with the higher rails

cheers sheafer
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Old 21st April 2012, 11:51 PM   #2
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all OK

increase both R6 & R7 (10K) for 35% or so

make them from 10K+3K3 (or 3K9) in series
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Old 22nd April 2012, 12:20 AM   #3
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thanks Zen Mod

great ,saves me mucho money on the toroids

i will no doubt have more questions as i get further through the build

many thanks
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Old 22nd April 2012, 12:26 AM   #4
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keep mosfets up to 45-50W of dissipation/each , well cooled
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Old 22nd April 2012, 12:33 AM   #5
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no probs
i am using 1x conrad 350mm x 150 per side , i am hoping to bias the hell out of this new amp

the sinks were just right for my aleph 2 which ran on the same rail voltage with the bias resistors removed (40 to 50 degres)

i,m hoping only running one pair output with the f4 will allow a higher bias to be run with the above sinks

cheers
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