AV400 - Page 2

nn20 · 5th August 2012, 10:49 AM

Hello

excuse me if it was asked before . I have some problem with my newly built av400 amp.i don't know how to set to multiturn potentiometer to access the best sound quality and avoid produce excessive heat on IRFPs.
I wonder if it's possible for you to help me how can i set it practically .
I was reading the instruction written by Mr holton but i didn't get the point.

whizgeek · 5th August 2012, 04:54 PM

measure the voltage across your 1ohm source resistors, adjust pot for your required current.
i would suggest 10mV as a starting point, check all devices at this level, they should be 9-11mV if matched sufficiently.
When you have finished build, then try adjusting to suit your taste, heatsink etc. many threads already on this topic.

nn20 · 5th August 2012, 05:08 PM

if you mention the 5-watt resistor of source pin of each MOSFET, it should be noticed that they're 0.22 ohm not 1 ohm. now do i make a mistake or you mention something else?

nn20 · 5th August 2012, 05:53 PM

fortunately I got the point .

but my resistor voltages are varied. i set the highest voltage on 18mv but the others are 9mv and 10 mv and even 3 mv . how can i match the MOSFETs together. and what happend if they still unmatched?

thank you for helping me.

nn20 · 6th August 2012, 08:29 AM

i've read the instruction for matching the MOSFETs but do i need more than 4pair of IRFPS to have the closest match or not?
could anyone explain how to match them?

ebix11111 · 02:31 AM

PCB AV400 R1 ؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟ ؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟

5th August 2012, 10:49 AM	#11
nn20 diyAudio Member Join Date: Nov 2011	help for bias setting Hello excuse me if it was asked before . I have some problem with my newly built av400 amp.i don't know how to set to multiturn potentiometer to access the best sound quality and avoid produce excessive heat on IRFPs. I wonder if it's possible for you to help me how can i set it practically . I was reading the instruction written by Mr holton but i didn't get the point.

2nd February 2013, 02:11 AM	#16
ebix11111 diyAudio Member Join Date: Feb 2013	PCB AV400 R1 ؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟ ؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟ Last edited by ebix11111; 2nd February 2013 at 02:31 AM.

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5th August 2012, 04:54 PM	#12
whizgeek diyAudio Member Join Date: Feb 2010	measure the voltage across your 1ohm source resistors, adjust pot for your required current. i would suggest 10mV as a starting point, check all devices at this level, they should be 9-11mV if matched sufficiently. When you have finished build, then try adjusting to suit your taste, heatsink etc. many threads already on this topic.

5th August 2012, 05:08 PM	#13
nn20 diyAudio Member Join Date: Nov 2011	if you mention the 5-watt resistor of source pin of each MOSFET, it should be noticed that they're 0.22 ohm not 1 ohm. now do i make a mistake or you mention something else?

5th August 2012, 05:53 PM	#14
nn20 diyAudio Member Join Date: Nov 2011	fortunately I got the point . but my resistor voltages are varied. i set the highest voltage on 18mv but the others are 9mv and 10 mv and even 3 mv . how can i match the MOSFETs together. and what happend if they still unmatched? thank you for helping me.

6th August 2012, 08:29 AM	#15
nn20 diyAudio Member Join Date: Nov 2011	i've read the instruction for matching the MOSFETs but do i need more than 4pair of IRFPS to have the closest match or not? could anyone explain how to match them?