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Old 8th February 2009, 11:56 PM   #2781
raxfor is offline raxfor  Bermuda
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hi

dose blanced f5 decrease noise?(like Differential input amp )or it just for more power?

Common Mode Noise dont influe on f5?
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Old 9th February 2009, 12:11 AM   #2782
Tea-Bag is offline Tea-Bag  United States
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Quote:
Originally posted by JimT
I have the Keystone 4661's and put a IRFP240 on it to check. The two small holes in the mica are low enough down that they are under the plastic part of the case just at its lower edge. The holes should not be an electrical problem.

Jim

Jim, thanks for checking!
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Old 9th February 2009, 12:06 PM   #2783
sekess is offline sekess  United States
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Default Regulated Supply

Has anyone built up an F5 fed from a regulated supply?

I was wondering if the advantages of a regulated supply would be heard in this case. The noise figure specs seem to be pretty good using a simple symmetric supply. But maybe with regulation the thing would become dead quiet.

Thanks,
Steve
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Old 9th February 2009, 12:24 PM   #2784
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Nelson himself suggested the possibility, and pointed to a couple of regulated supplies in the Zen articles.

I've been pondering the Teddy Pardo Powerreg from pinkfishmedia, but don't know if the pass resistor can really stand up to the large current demands of the F5. Let us know if you give a regulated supply a try.
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Old 9th February 2009, 12:31 PM   #2785
sekess is offline sekess  United States
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Default regulated supply

I'm thinking about it. I'm a little hesitant because of the extra heatsinking for the power supply. It might almost be worth it to put the power supply in it's own seperate case and feed the amp via an umbillical.
The amp itself could be in a smaller case of course.

I have to ponder a bit more.

Steve
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Old 9th February 2009, 12:54 PM   #2786
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Default Re: Regulated Supply

Quote:
Originally posted by sekess
Has anyone built up an F5 fed from a regulated supply?

I was wondering if the advantages of a regulated supply would be heard in this case. The noise figure specs seem to be pretty good using a simple symmetric supply. But maybe with regulation the thing would become dead quiet.

Thanks,
Steve
The noise is pretty low -- NP indicated 100uV with 29mF filter caps --

If you use a regulator, the pass devices should be capable of handling 5 amps peak on each side.
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Old 9th February 2009, 08:05 PM   #2787
sekess is offline sekess  United States
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Default regulated supply

If each device would be capable of 5 amps peak per side and the rule of thumb for a regulated supply is to give it at least 10 times the capacity of what the ampis rated for, then I would need 3 pairs of MOSFETs in the supply -- since the amps output devices are drawing 1.3Amps per device at idle.

Does this sound about right?

If this is correct, that amounts to pretty huge power supply for a 25 watt per channel amplifier.

Steve
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Old 9th February 2009, 08:10 PM   #2788
sekess is offline sekess  United States
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Oh wait,
I think I misunderstood what you said. Your saying that the capacity of the supply MOSFETs should be 5 amps for the F5 -- in that case, I'd be ok with one pair of IRFP's per power supply per channel.

Steve
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Old 9th February 2009, 08:32 PM   #2789
amp_guy is offline amp_guy  United States
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Of course dissapation can be fairly low in regulators , depending on what voltage your raw supply is at . You may not need that much sinking. Are you thinking tight regulation or mostly capacitance multiplication?
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Old 9th February 2009, 08:38 PM   #2790
sekess is offline sekess  United States
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I was thinking capacitance multiplication. But, I have not decided yet. I was trying to get a feel for what a regulated supply build would entail and if the extra effort would yield a significant enough improvement in the sound.
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