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Old 9th June 2008, 06:49 PM   #61
Mooly is offline Mooly  United Kingdom
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Hello PA,
To get the speed from FET's requires quite specialised drive circuitry. The gate is seen as essentially capacitive and it's how quickly you can pull charge to and fro thats the real problem.
Driving even 1nF at say 50 Mhz with a 10 volt swing takes some serious consideration.
Regards Karl
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Old 9th June 2008, 06:54 PM   #62
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Quote:
Originally posted by Mooly
Hello PA,
To get the speed from FET's requires quite specialised drive circuitry. The gate is seen as essentially capacitive and it's how quickly you can pull charge to and fro thats the real problem.
Driving even 1nF at say 50 Mhz with a 10 volt swing takes some serious consideration.
Regards Karl

You really dont need 50MHz in an amplifier, its more like to cause more problems than it fixes.

If it works to 50KHz at full bore then it will drive most speakers and tweeters.

I get away with whacking 12mA into 6 MOSFETS and my amp sounds great.
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Old 9th June 2008, 07:00 PM   #63
Mooly is offline Mooly  United Kingdom
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50Mhz is R.F not A.F. no place in audio amps.
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Old 9th June 2008, 07:04 PM   #64
Mooly is offline Mooly  United Kingdom
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PA,
The data sheet for the 2SK1058 has a quoted on time of 180 nano seconds and 60 nS off time. I have seen figures of 100 Mhz bandied about for lateral FET's like these.
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Old 9th June 2008, 07:35 PM   #65
alex mm is offline alex mm  Europe
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Default PCB for Mooly amp

Hi all ,
PCB not tested, but possible working http://i30.tinypic.com/f3gv80.jpg
regards alex mm
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Old 9th June 2008, 07:39 PM   #66
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Default Re: PCB for Mooly amp

Quote:
Originally posted by alex mm
Hi all ,
PCB not tested, but possible working http://i30.tinypic.com/f3gv80.jpg
regards alex mm

Can you not add a ground powerplane to your PCB ?

I never put fuses on my PCB's, as I run a disco I need quick access so they are on the outer panel.
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Old 9th June 2008, 08:06 PM   #67
AndrewT is online now AndrewT  Scotland
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I looked at the JLH a long time ago, but was never tempted.
I looked again soon after joining this Forum but again didn't jump in.
I am a fan of his, typical of the "British design" breed.

But, this time I'm tempted, by both latest of the original and your version.
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regards Andrew T.
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Old 9th June 2008, 09:35 PM   #68
KLe is offline KLe  Australia
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Default Re: PCB for Mooly amp

Quote:
Originally posted by alex mm
PCB not tested, but possible working http://i30.tinypic.com/f3gv80.jpg
regards alex mm
Nice job Alex
Keep us posted of how everything goes ... we are all ears

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Old 9th June 2008, 11:26 PM   #69
KLe is offline KLe  Australia
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Hi Andrew

Nice to see your interested ...

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Old 9th June 2008, 11:29 PM   #70
KLe is offline KLe  Australia
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Hi Mooly

Question: If the output Lfets idss's are matched, do you still need R23 & R24 ...

Also, is the position of R26 correct ... it's showing that it is in series with L1 ... Alex, your PCB digram doesn't show R26 (or I can't see it?) ...

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