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Old 22nd February 2003, 08:53 PM   #21
Nicwix is offline Nicwix  Australia
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Jay

I did try him (Kirchoff, that is), but he was not very approachable ...

Nic
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Old 22nd February 2003, 10:18 PM   #22
Jay is offline Jay  Indonesia
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I made my quick "calculation" based on simple logic. The circuit has a physical layout that almost "symetrical": 1/4W resistor - Vds - Vds - 1/4W resistor.

Whatever the DC rail, the input should have only a few mV above ground, right? With Vgs around 3 to 4V, the Drain of current source should at most 5V above ground. Then how do you share a 25V between Vds and a 1/4W resistor? (assumming a 30V rail)

I'm not good at electronics, so would you look at it for me once more, please?
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Old 23rd February 2003, 03:48 AM   #23
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These Mosfets Do Not need a heat sink.
I have a genuine Aleph 5; it does not have heat sinks on these mosfets. The mosfets stand off the board vertically.
I have built two mono Aleph 2 clones with no heat sinks on these mosfets.
All are working.

Good Luck
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Old 23rd February 2003, 03:45 PM   #24
Jay is offline Jay  Indonesia
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Agree with JoeD. You don't need a heatsink.

In my case, I use a 40V-0-40V transformer. Originally, I didn't use any heatsink, and I used a resistor to offset the DC in the current source. Later, I removed the resistor and put a heatsink on the ccs MOSFET.

What is the specified rail for Aleph2? 30V? 35V? If 35V, I believe there is a considerable amount of heat. You can do the math if you think it is worth to do
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Old 23rd February 2003, 03:51 PM   #25
Jay is offline Jay  Indonesia
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Oh, may be I can find IRF9610 with the highest Vgs for the ccs. Does this make sense?
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Old 6th May 2003, 03:18 AM   #26
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Hi,

Regarding in this old thread, I have a question.
After powering up my aleph 60, it starts just right up.
The sound is audible, but after a few minutes, one of the diff pair become very hot, Q2. Q1 doesn't get even hot, but they are matched pairs.. Q3 also gets hot, but thats logical.
When powering it down with the variac, the sound is very long audible, but there is 140.000mF p/ch.
By the way, I left out the resistor R0 out, wich is 3@3W.
Is this the reason for the heat differential?
I'm not using heatsinks for these pairs.

Thank you,
Remco
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Old 6th May 2003, 07:43 AM   #27
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Are you drive it in single ended mode or balanced mode?
If you drive it in single ended mode, you should take a jumper in balanced input negative side to ground (as it is written in manual).
Small heatsink is preferred for Q1-Q3, R0 recommended (in my opinion).
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