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It is currently 18 Sep 2019, 23:53

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PostPosted: 09 Mar 2019, 18:41 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
Nice build. I would think you would need a lot more heat sink but if it works that way good!

Do try the MCA with a jfet2N3055 Darlington pair. I think it sound better and runs pretty cool.

Also the input cap to the ZCA should be 0.1uf NOT 0.47uf. 0.47uf is way too big and causes sevear roll off of the square wave at low frequency.

Easy enough to change.

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PostPosted: 17 Mar 2019, 12:10 
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Joined: 25 Dec 2018, 08:41
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I tested the ZCA for 90 mins in a room at 24°C.
The temperature rose to 51°C. See Diagramm. The whole surface is a 8mm 20cm x 30cm massive Al-sheet. I have not that experience in building amplifieres, but I hope 50°C and maybe 60 °C in summer are save??????????

I bought the 2N3055 and JFETs already. You can see the therefore prepared screwholes on img4 above the 2sk1058.
I reduced the input-cap, but do I also have to reduce the 1k resistor to 220R ?

Gerti


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PostPosted: 17 Mar 2019, 12:36 
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Joined: 06 Apr 2009, 10:08
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Location: US Pacific Northwest
Gerti wrote:
The temperature rose to 51°C.
You need better heatsinks. Bare aluminum sheet has a rather low emissivity. Invest in some higher emissivity heat sinks and that temperature should come down appreciably.

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PostPosted: 17 Mar 2019, 16:26 
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The ZCA will run pretty hot and the only way to control that is with a proper and big heat sink. Remember electrical isolaction from the heat sink.

You only have to reduce the input cap.

The MCA runs a lot cooler.

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