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Old 7th February 2002, 09:20 PM   #21
Helix is offline Helix  United Kingdom
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no offence or anything, but wouldn't it be better to have the PS input at one end of the cap rails and the output to the amps at the other, from what i can tell they are hooked up on top of each other!
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Old 7th February 2002, 09:54 PM   #22
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Default Amp Pics

Jet-Mosfet cascode front end, Mosfet gain stage, Class A IXYS Mosfet output. No global feeback except for DC offset. Toshiba, Zetex,IR,and IXYS fets. Holco, Caddock, and Dale wire wound resistors, cardas jacks, silver clad telflon wire. Rifa, Spague 36D, and Panasonic caps. LC filtered seperate supply for front end.

H.H
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Old 9th February 2002, 12:37 AM   #23
Helix is offline Helix  United Kingdom
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my amp is here :
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Old 9th February 2002, 01:38 AM   #24
BrianGT is offline BrianGT  United States
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Yeah, my amp is here:

--
Brian
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Old 12th February 2002, 10:01 PM   #25
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Default One Amp I made for a friend

Hi folks,

I hope attaching an image works.

This is a rather big Amp I made for a friend. It can deliver 2*450 Watts at 4 Ohms if a fan is attached to the heatsinks.
It is a bridge Amp, intended for PA rather than for home, but it sounded surprisingly good.

Inside there are the bridging circuit, a symmetrical folded cascode gain stage, IRF540/9540 output FETs, softstart and security functions.

Not a high end project, but quite powerful.

At this time I am working on a more audiophile Amp with less power but more linearity and low noise.



Ciao and happy listening
Andy
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Old 12th February 2002, 10:30 PM   #26
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Default Re: One Amp I made for a friend

Quote:
Originally posted by AndyM
Inside there are the bridging circuit, a symmetrical folded cascode gain stage, IRF540/9540 output FETs, softstart and security functions.
Andy
Hey would u be kind enough to let me have a look at the schematic for one of the amp modules (not a bridged pair)? I built an amp using the IRF540/9540's (two pair per channel) and had a hard time getting crossover distortion eliminated without heavy bias -- too much bias for my likings. I eventally used more expensive MOSFETs.

Looks good!
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Old 12th February 2002, 10:35 PM   #27
UrSv is offline UrSv  Sweden
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Fleming J P,

Do you know if it is the Alexander Amplifier or The End Amplifier featured in High Fidelity? I have the old issues and have though on many occasions about building them.

/UrSv
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Old 13th February 2002, 07:14 AM   #28
Jason is offline Jason  Australia
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My amp is <a href="http://www.diyaudio.com/forums/showthread.php?threadid=914">here</a>:

Unfortunately I never quite got around to building my own
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Old 13th February 2002, 08:42 AM   #29
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Quote:
Originally posted by UrSv
Fleming J P,

Do you know if it is the Alexander Amplifier or The End Amplifier featured in High Fidelity? I have the old issues and have though on many occasions about building them.

/UrSv
Neither I think. I know that they were designed by Mogens Meilvang Andersen and that it is his 3. generation amp. The article I saw in High Fidelity didn't show any schematics. As far as I remember the title was "køkkebords højtalere".

If you want, I can scan the schematics and post them.
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Old 13th February 2002, 09:41 AM   #30
sonnya is offline sonnya  Denmark
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Flemming is right. The amp Flemming has was mentioned was only part of an article about hififreaks..

Sonny
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Old 13th February 2002, 01:35 PM   #31
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Randy,

as for a PA Amp, distortion was not the main focus...
I chose the IRF-types because of their ruggedness.
I will post the schematic tonite, because right now I am at work. I don´t have the original anymore, but I think I can reconstruct it.

Which FETs did you choose, because I want to use MOSFETS in my current project too? For this, distortion really is an issue.


Ciao
Andy
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Old 14th February 2002, 12:12 PM   #32
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Default Schematic

Randy,

here is the schematic you requested. It was years ago, but it was something like that.

Bias was not very high, about 150 mA. Which bias did you choose to minimize crossover distortion?

Ciao
Andy
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Old 14th February 2002, 02:42 PM   #33
Helix is offline Helix  United Kingdom
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no input cap? what happens to DC?
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Old 16th February 2002, 03:31 PM   #34
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There was a bridging circuit at the input which had an output capacitor.
Anyway, the schematic lacks some details, as current-limiting and others.
Even without correcktion, DC at the output was no problem, just 50 mV or so.

Andy
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Old 25th November 2002, 07:28 PM   #35
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Default my second amp

Hi all,

finally got my digital camera back so now I can post some pictures of the amp I´ve been modifiing and rebuilding for about 17 years. It´s based on the elektor Crescendo but with some different parts, regulated power supply (drivers only), dc-servo and 6 instead of 4 fets per channel.
Main power supply is two times 500VA transformer, discrete bridges and 100mF per channel. Power is 70watts/8 Ohm and 136 watts/4 Ohm. Bias is 1A, so up until about 16watt/ 8 ohm it´s class A going to AB after that.

The case is made out of 5mm aluminium, the front is 10mm thick.

william
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Old 25th November 2002, 07:32 PM   #36
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another picture without the lid on shows the two main boards.

The bridges and transformers are below these (shielded), the compartment in the back hold the two transformers for the regulated supply and the 12V supply, softstart and fuses
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Old 25th November 2002, 07:36 PM   #37
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and the printed circuit (doublesided) in detail. It was done with a very old version of protel without the ability to do ground planes wich was a bit difficult.....
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Old 25th November 2002, 07:38 PM   #38
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and one from below showing the caps (hard wired on two pieces of perspex)
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Old 25th November 2002, 07:41 PM   #39
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Wow! Very Nice!
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Old 25th November 2002, 07:55 PM   #40
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Very nice indeed. How those caps perform after all those years? I was thinking about something similar on my future Aleph X (3300u/25V x 40 per channel). Is it a good idea?
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