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Old 20th August 2003, 05:36 AM   #1
Jaskier is offline Jaskier  Poland
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Question Fet on a wire :-)

Hi,

I have just finished my Aleph 5 clone and managed with problems of flat sound stage I had. (Higher bias helped).

Even though I still have some dilemma. I used Mark Finn's PCB but I did not manage to get big enough heat sinks. Therefore, I decided to make a mono-block with chassis built of smaller heat sinks. However, here lies the problem (or not a problem) I had to place FET in some distance from PCB so I used 1 sqmm ofc wire to do so.

Some of people I know suggest me to move 0,68 ohm (source) and 221 ohm resistors next to fets. However, honestly speaking I do not see any reason to do so (besides I am a kind of lazy man). Than again, this little dilemma makes me nervous a bit. So please if anyone has any suggestions ... just post it.

Piotr
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Old 20th August 2003, 06:03 AM   #2
Jaskier is offline Jaskier  Poland
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FET on a wire ... chasiss before painting.
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Old 20th August 2003, 06:57 AM   #3
wijgers is offline wijgers  Netherlands
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Very nice amps, the looks.
Great Job you did there.

How is the sound? like the others?

As you see in other treads, pictures of Aleph 5, some people use fets on a wire. Although the resistors are also placed near the fets and attached on a wire. I don't think it is a big difference if only the fet is on a wire at the heatsink.

Good luck,

Nils
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Old 20th August 2003, 07:33 AM   #4
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Hi Jaskier,

First, I have to say : "Great looking amps !" Nice work, indeed. More photos, please !

Regarding your dilemna, you sure have to locate the gate resistors (221R) as close as possible to Fets. These resistors aim to avoid oscillations of fet stages by damping the parasitic input inductance and capacitance of the fets. If the resistors are located far from fets, the inductance of the connecting wire adds to the fet's one, and damping is far less efficient.

Location of the source resistors is - IMHO - less critical, but with such low resistor values (0R68), use a very low resistive wire and make sure to use the same wire lengths everywere to add the same amount of resistance to every resistor.

Hope this helps.
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Old 20th August 2003, 11:08 AM   #5
Bricolo is offline Bricolo  France
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Beautifull stuff!

Can you post a picture of the piece of furniture (without the amps), please?
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Old 20th August 2003, 12:39 PM   #6
Jay is offline Jay  Indonesia
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Wow! Very classy build! (And also the stand). And I agree with Cheff about the gate resistor.
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Old 20th August 2003, 01:37 PM   #7
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Great job but I must agree that the gate resistors should be directly connected to the fets.
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Old 20th August 2003, 02:38 PM   #8
MikeW is offline MikeW  United States
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Great job. I am glad you fixed your problem. Enjoy.
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Old 21st August 2003, 05:30 AM   #9
Jaskier is offline Jaskier  Poland
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Thanks for advice. I reorganized my Aleph (inside) and moved gate and source resistors directly to fets. The difference in details is just incredible. Now I can close covers and enjoy the music ƒº. Here is picture of my ¡§music¡¨-room. Not everything is ready. Some damping units are still missing.
Again thanks for help. Now I would like to make an Aleph X. Does anybody have a good link for page with schematics, PCB¡¦s and construction notes ?
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Old 21st August 2003, 05:46 AM   #10
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Bare necessities are sometimes the best
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