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Old 18th April 2013, 04:37 PM   #1
jgf is offline jgf  United States
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Default Potted choke orientation/amp layout

I'm planning a push pull 6550 stereo amp... here's my layout so far. Any thoughts on the choke orientation or an educated guess on the coil winding direction? The choke is the gray potted can. The front row of sockets will be 6sl7 into 6sn7.

The outputs are dynaco 430 and 431, the power transformer is hammond 378cx, The choke is 3.8h @ 550ma DC (33 ohm), and the transformer on the front left is 6.3volt. I may use the 6.3v 6ma of the hammond in combination with another under-chassis transformer instead.
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Feedback appreciated!
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Old 18th April 2013, 09:09 PM   #2
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With your potted choke , and that far away from the output transformer and having a cap input orientation won't make and difference , the power transformer will be the major factor for magnetic induced hum .

What circuit are you going to use .

Mark
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Last edited by battradio; 18th April 2013 at 09:12 PM.
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Old 18th April 2013, 10:01 PM   #3
jgf is offline jgf  United States
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Hi Mark, Thanks for the reply. I remember your moniker, I hope those power transformers I sent you are working out ok!

So I don't need to worry about coupling between the choke and PT? I have about an inch between the PT and left OT so hopefully that will be enough space. I could maybe squeeze over further, but I've got SDS cap boards built up which will sit under the opts (all sections parallel for outputs) so that's another space constraint.

Yes, I'll have a cap input, about 10 or 15uf before the choke. Typical fixed bias output with triode/UL switching, I'm thinking 6SL7 differential --> 6SN7 differential for the input but I haven't decided finally yet, I may try some things and tweak. For inspiration, I'm looking at Morgan Jones Crystal Palace, KTA mark III, and a thread around somewhere with a Tubelab design using those tubes and mosfet powerdrive. John

Last edited by jgf; 18th April 2013 at 10:04 PM.
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