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.)
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...
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...
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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.
...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?
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?
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.
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.
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.
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
I paralleled the sj74's in my AJ monoblock's FE. I was running three output pairs. 109 is better of course, if you got them. ZM is always talking about liking lots of current. I believe Nelson says more current allows reduction of Rl and gain and better linearity. Don't quote me though, bad memory.
Looks great and plus, he drew it. No current limiting stuff on bottom end. I think the extra current/paralleled inputs in the J2 was for optimization of that circuit, so go with what he gave you. Cant get any better than a personalized schematic by the guru. You can use one matched pair of SJ74 unless you have and want to use a single 109. Phenomenal build diary on your other stuff. Very helpful for other interested in the DIY game.
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You can run enough current through the 2SJ109 to do the job - I paralleled
them just because I can.
cool, thanks, i selected some matched high idss j74 quads so i'll probably parallel them too
you can use either, i actually think thermally bonded well matched singles are better, j109 arent always a great match.
The saga continues...
Here are my Peter Daniel boards I bought from a member in Holland. The only ones that anybody had for sale were stuffed, with tightly-matched 240's, and neat parts like Silmics and such. Saves me a digi-key order, I like that.
I will have to remove a few components (limiter circuit, the power Fets) and replace a resistor with a pot in order to match it to the schematic that Nelson drew.
Then it's off to chassis fabrication, I have the important parts, and am hopefully going to meet with a machine shop today.
Here are my Peter Daniel boards I bought from a member in Holland. The only ones that anybody had for sale were stuffed, with tightly-matched 240's, and neat parts like Silmics and such.
Saves me a digi-key order, I like that. I will have to remove a few components (limiter circuit, the power Fets) and replace a resistor with a pot in order to match it to the schematic that Nelson drew.
Then it's off to chassis fabrication, I have the important parts, and am hopefully going to meet with a machine shop today.
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