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Old 3rd October 2011, 09:03 PM   #1
6L6 is offline 6L6  United States
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Default The Aleph Jango

So I went to Burning Amp, had a fantastic time, and came home with some treasure - (Thanks to our spiritual, technical and menu advisor, Nelson Pass.)

Click the image to open in full size.

That's a matched quad of SemiSouth power Jfets and the Toshiba diff. pair driver.

This will be the heart and soul of my AlephJ, which, if you think about it, will actually be an Aleph JJ !! How cool is that!?!?

Hang tight, this is not going to happen overnight, but I am collecting parts as we speak.

Oh - a quick explanation of the name - There is a Star Wars character named "Jango Fett". Also Jango is pronounced the same as Django Reinhardt's first name. So, in a certian light, and with a little obscure knowledge, it makes sense in my mind, anyway...

Or I could just call it "The Ultimate Hedgehog" for reasons you haven't seen yet...

Last edited by 6L6; 3rd October 2011 at 09:14 PM.
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Old 3rd October 2011, 11:44 PM   #2
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Read post 2. Perhaps you know already, but it will take some changes. FLG posted a possibility using two billowed in ACS. I am sure nelson thought about AJ when looking at SS fets, but came up with J2 to use them in optimal setup. Then again, two circuits are close in nature than one might think.
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Old 4th October 2011, 04:22 AM   #3
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I recall the 6L6 is planning on 2 parallel Jfets and 2 Mosfets in parallel for
the current sources in each channel.

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Old 4th October 2011, 04:34 AM   #4
6L6 is offline 6L6  United States
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...which is to say (except for the power Jfets...) the 'normal' AlephJ, right?

Oh, as long as I have got you here... do the current sources or the output transistors burn more current? I.E., which need more heatsink? Or is this a matter of two sides of the same coin, and they both do about the same?
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Old 4th October 2011, 11:06 AM   #5
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It's Pass style push pull. Both transistors will see same current and same rail voltage and dissipate same heat, right?
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Old 4th October 2011, 11:25 AM   #6
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Actually, it depends on how you have the ACS setup. As it is in the schematic, I believe that it is 47% or thereabouts, meaning it will basically double output of lower half. You can set it higher and current output will increase with ADS contributing more than half of total available current. It is a wonderful amp.
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Old 4th October 2011, 11:44 AM   #7
flg is offline flg  United States
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You generally set the node between the A CS and the gain FET to 1/2 the rail. About 0 in this case. Statically they will burn the same power.
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Old 7th October 2011, 04:01 AM   #8
6L6 is offline 6L6  United States
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Well, I found a guy who was willing to sell his Peter Daniel boards. They are stuffed, and have the 2nd set of output FETs, so I will have enough matched 240's for another amp! Neat.

Anyway, I've been looking at the heatsink configuration and doing some research, and have come to the conclusion that I'm going to have to build a mount or a PCB to get the filter caps on top of the transformer - there just isn't room for them to be on the baseplate. Not a big deal, just another step.

I've decided that this amp is not going to have any corners cut, and my mantra of 'done is my favorite color' is not really going to apply. I want to do this one better than 'good enough'. I'm not going to gold plate it and get crazy with components (I mean, of course, other than the unobtanium jfets...) but I want it to be really nice, and worthy of Nelson's generosity.
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Old 7th October 2011, 04:24 AM   #9
qusp is offline qusp  Australia
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very interested in this, normally an aleph j only has the single jfet differential as input, you need the 2 in parallel to get enough current for the r100. i wanted to do this myself and have put my aleph jx on hold for a bit, all that was left is casework and installing the matched fets, so i'm watching with interest. the ajx is already a bit edgy as far as setup, so i'll appreciate someone else doing the hard work with the SS version =) i'll probably use the R100A though
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Old 7th October 2011, 04:49 AM   #10
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You can run enough current through the 2SJ109 to do the job - I paralleled
them just because I can.

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