Aleph J

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Oh Oh.... There will be a lot of folks pitching the current crop of Aleph30 boards from the current miniAleph GB in a few months for the J version when the service manual comes out!

I cannot imagine how Nelson will beter himself with the Aleph J! The Aleph30 is pretty damn good!

I quess that's why we call him the master.

-David
 
I find it interesting that no one has asked why the Aleph has the moniker "J". Could it be:

1) that the input transistors are JFET's (which would definitely require cascoding in a higher output version),

2) or does the "J" honor Ms. Pass who is the real owner of the kitchen table upon which these new creations are built?

It'll proboly be revealed in the service manual I imagine!

Cheers,
GL
 
Been there, done that, at least on the bench. I have yet to make up a 'real' amp that I could listen to. You run into two problems:
--As Nelson alluded to, the part can't take much voltage. This will limit the rail voltage, which in turn limits the eventual power output. Yes, you can do an Aleph-X bridged circuit, thus gaining four times the power (assuming sufficient bias) but even then you're going to run into the limits fairly quickly. You can cascode. You can go to three stages, limiting the rail on the front end differential, then allow the second stage a bit more breathing room...etc. But then you're getting off the beaten path, which will take some of the K.I.S.S. out of the topology. i.e. it will no longer be a two stage amp.
--It's not all that sterling at taking current, either. This limits the number of output devices that you can expect to drive with it. Yes, there are higher and lower current grades of the piece, but the damned things are getting hard to find--supposedly discontinued--and more expensive by the day. Furthermore, I have yet to find a place that will tell you which of the three current ratings they have in stock and let you choose which you want to order. You're ordering a pig in a poke. Granted, this is understandable in the business sense, in that everyone would buy the highest current version available, whether that was what they actually needed or not. Still, it's a pain in the rump to have people play coy with you. Sure, you could put a follower after the differential, but again, you're changing the original topology.
That said, there's no reason that you can't change the topology if you want (e.g. Aleph-X). If you're willing to fiddle about with the front end and/or take biasing of the output stage into your own hands, you can do all sorts of things with an Aleph. Some of them even sound pretty decent. I've done a bit of this and that and may start a thread on Aleph variations when I've got a bit of spare time.
Incidentally, the 2SJ109 is not only a "J"FET, it has a J in its name, which makes it doubly appropriate.
One can only hope that Toshiba either does another production run or comes out with a new-and-improved part to replace the 2SK389/2SJ109. But...as I've said many times before...I ain't gonna hold my breath. There's quite a distance between wishes and reality.

Grey
 
Those are all valid thoughts.

It's not really worth speculating too much on the small teasers the man has tossed out, but it would be fair to assume that he's probably going to use the same box and transformer he used for the F1 and F2. The Aleph 30 uses 25V rails like the F2 and presumably the F1. So yes, running a 2SJ109 at 25V with enough current to drive 3 IRFP240's is asking a lot unless there are fun new things afoot. And that's not at all unlikely.

He's only building 100 of them I presume, so laying in a stock of 100 2SJ109's would not be a hardship. I would guess that Passlabs has a serious stash and that they might share.

And yes, I did notice the double J thing as well.

I can't help but feel that the Aleph J might just be a very popular piece - both on this website and off.

Cheers,
GL
 
dw8083 said:
Oh Oh.... There will be a lot of folks pitching the current crop of Aleph30 boards from the current miniAleph GB in a few months for the J version when the service manual comes out!

I cannot imagine how Nelson will beter himself with the Aleph J! The Aleph30 is pretty damn good!

I quess that's why we call him the master.

-David

Nah!! Id like to build one though : O ) in this picture.. It looks like hardly any parts : )
 

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Popular among us, perhaps, but we represent only a miniscule fraction of a fraction of a fraction of...of one percent of their overall business. Even if you count all the high end manufacturers, it's a drop in the bucket to a multinational corporation.
We were lucky to get them in the first place.
As for how many parts are required--I remember a thread wherein someone mocked me because I brought up the idea that you might want to keep some parts around for servicing equipment in the future. Perhaps he'd never heard of warranties. Perhaps he was unaware that they are enforced by laws. Naturally, you want to design things so that the user experiences as few failures as possible. Better for the consumer and better for the manufacturer. Still, it's not a bad idea to have several percent more parts than you need for the production run. Even if it isn't a warrany repair, there are always those who manage to short the output or spill a drink in the unit while it's running. Assuming a production run of one hundred units (plus a few protypes and one-offs for friends), that's not such a burden. However, I believe Nelson's using the 2SJ109 in some of the X product as well. Suddenly his reserve against failures begins to rise.

Grey

P.S.: The more imaginative will at this point begin to wonder what the back room at, say, Pioneer, Sony, or Yamaha must look like. Just to further rattle your cage, consider that they most likely sit on some parts well past the warranty period for the equipment in question.
Power JFETs, anyone?
 
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