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Old 2nd December 2007, 09:37 AM   #1611
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Carpenter,
it will sound better still when it gets really hot (+55*C)!
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Old 2nd December 2007, 05:54 PM   #1612
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Quote:
Originally posted by Babowana




Did you use all matched MOSFETs?



I matched N fets to N and I matched P to P. The P channel VAS test result is 0.18 volts apart from the N channel.

I also match (ohm wise with a multimeter) all resistors that have a mate.

I made no attempt to match jfets. I just asked them to be blessed with the loving energy of the "golden ears" spirit.

The amp does hit the 50 degree mark, but holds steady--in fact, I'd swear that the fets get cooler when the amp is playing music.
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Old 2nd December 2007, 06:06 PM   #1613
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Default N to P matching

Quote:
Originally posted by carpenter



I matched N fets to N and I matched P to P. The P channel VAS test result is 0.18 volts apart from the N channel.


Hi,

what about N to P fets matching, does it make sense or not for f4?

Regards,
Andrzej
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Old 2nd December 2007, 06:57 PM   #1614
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Quote:
Originally posted by carpenter



I matched N fets to N and I matched P to P. The P channel VAS test result is 0.18 volts apart from the N channel.

I also match (ohm wise with a multimeter) all resistors that have a mate.

I made no attempt to match jfets. I just asked them to be blessed with the loving energy of the "golden ears" spirit.

The amp does hit the 50 degree mark, but holds steady--in fact, I'd swear that the fets get cooler when the amp is playing music.

I think that I sent you matched 170/74 ; P to N
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Old 2nd December 2007, 07:06 PM   #1615
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Thanks, Choky. I forgot
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Old 2nd December 2007, 07:08 PM   #1616
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Default Re: N to P matching

Quote:
Originally posted by Andrzej Sochon



Hi,

what about N to P fets matching, does it make sense or not for f4?

Regards,
Andrzej

Not in my case. I'm using P channels that are 0.18 volts apart from the N channel and only have 1 mV offset drift after P2 correction.
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Old 2nd December 2007, 07:08 PM   #1617
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Default Re: N to P matching

Quote:
Originally posted by Andrzej Sochon



Hi,

what about N to P fets matching, does it make sense or not for f4?

Regards,
Andrzej
You can match the N's to the P's if you like, the advantage will be (probably!!) less offset at the output. In any case, it will never hurt, whatsoever.........


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Old 2nd December 2007, 07:26 PM   #1618
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A couple of pic from my test bench (note the TO-220 fet pkg):
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File Type: jpg f4 on tower.jpg (75.0 KB, 717 views)
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Old 2nd December 2007, 07:27 PM   #1619
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Here's a Wakefield 392-300AG heatsink given to me from a fellow carpenter. He had no idea what it was, but thought I might be able to put it to good use.

I purchased a mate for it at a cost of $160.00. This will be my first F4. For the rest of the F4s, I'm going to play with water cooling.

Caps in PS are 47,000uF each.
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Old 2nd December 2007, 07:33 PM   #1620
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Default Re: Re: N to P matching

Quote:
Originally posted by carpenter

Not in my case. I'm using P channels that are 0.18 volts apart from the N channel and only have 1 mV offset drift after P2 correction.
0.18 volts you got per accident or you ordered or choosed or selected such an exact 0.18 V combination of P and N channel? Could it be 0.15 or 0.21 Volts for instance? (As far I understand 0.15 is better).

I try to understand what do I need to look/ask while ordering the set of IRFP's for my ballanced f4, two channels. In other words what is the most important: N to N matching (4xNNN in my case) and separately P to P matching (4xPPP) or matching all together what seams me to the best but probably not available for me (4xNNN AND 4xPPP). I see the IRFP240 and IRFP9240 curves are different. Sorry my language...-
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