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Old 30th December 2015, 09:30 AM   #1
GeeVee is offline GeeVee  Australia
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Default Pass Aleph 2 with IRFP 140.

Hi all.
I am fast approaching completion of my Aleph 2 amplifier, and would like comments regarding the usage of IRFP 140 devices.
I will be running about +40 to 45 vdc rail.

According to the data sheet, this should be OK.

My choice for this device is based on nothing more than having hundreds of these devices here ready to go. (Subject to matching).

Could someone please tell me if the usage of this device will be OK?

Kind regards.
George
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Old 30th December 2015, 09:42 AM   #2
vivanco is offline vivanco  Italy
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I take this opportunity to ask what is the value of voltage drop across the resistor source dell'Aleph 2 ?
I have to make the test measurement on my aleph 2

thanks
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Old 30th December 2015, 09:42 AM   #3
Zen Mod is online now Zen Mod  Serbia
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just go for it

consider decreasing gate resistors to 150-180R

observe stability

don't skimp on 1nF anti-oscillation caps

to vivanco - 500mV across 1R source resistors
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Old 30th December 2015, 09:48 AM   #4
vivanco is offline vivanco  Italy
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hi Zen Mod, What do you mean by capacity anti-oscillation (1nF) ?
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Old 30th December 2015, 09:52 AM   #5
Zen Mod is online now Zen Mod  Serbia
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show me schematic you're using and I'll show which caps
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Old 30th December 2015, 10:00 AM   #6
vivanco is offline vivanco  Italy
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this is Pass Labs ALEPH-2 DIY amplifier KK-PCB layout
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Old 30th December 2015, 10:16 AM   #7
Zen Mod is online now Zen Mod  Serbia
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two red dots

also - instead of 390R resistor , put 500R multiturn pot (preset to 390 or so ohms) , for fine output offset set
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Old 30th December 2015, 10:29 AM   #8
vivanco is offline vivanco  Italy
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ok perfect,,, you can also tell me what is the value of volts that must be measured at the ends of the source resistance (1 ohm) ... I ask because I measure an average of about 3.7 V
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Old 30th December 2015, 10:46 AM   #9
Zen Mod is online now Zen Mod  Serbia
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I already did - in post #3

3V7 is bloooooody too much!!!

something is wrong , not just setting

start new thread , put plenty of pictures and we can (hopefully) help
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Old 30th December 2015, 10:50 AM   #10
vivanco is offline vivanco  Italy
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in your opinion what type of capacitor should be used (I mean those with value 1 nF)
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