First Watt J2

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iansr
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#1 First Watt J2

Post by iansr »

Mr Pass's other new creation - the J2 - only has a measly 4 JFETS, but they are very special JFETS indeed, with a price to match. There is a group buy building up at the moment on diyaudio, estimated price $50 each (sic) if anyone is interested. Super expensive for a transistor, but what would you pay for an exceptionally good valve . . .

Anyways Nelson reckons the J2 is the best First Watt yet, which means its must be an outstanding amplifier, and 25 wpc to boot.
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ed
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#2

Post by ed »

yeah but no but yeah but.......

Papas being a bit more cautious with this one, there won't be any schematic until the last one has gone out of the production shop

+

the semisouths are not actually available yet and he has the first order for them

+

he's teasing the OT mob to try and second guess the actual schematic from the modular diagram in the owners manual....

this all adds up to a non practical projatct at the moment afaics cos there will be a few expensive guesses to begin with......

unless I've missed something more recent
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iansr
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#3

Post by iansr »

Ed
you are right, he has got p****d off with people ripping off his designs so he is going to build/sell 100 before he releases the full schematic. I don't reckon it will take him long to do that. In the meantime the Group Buy organiser does seem to be in a position to make a bulk purchase.

cheers
Ian
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Nick
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#4

Post by Nick »

Nice, solid state µ follower, though the block diag looks more like a SRPP. There is almost the same shape on page 6of the device specs

http://www.semisouth.com/products/uploads/AN-SS1.pdf
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iansr
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#5

Post by iansr »

Some extracts from the FW Information Sheet on the J2 (minus the diagrams referred to):

Here is a slightly simplified schematic of the J2 circuit. It could be a classic tube amp, except that the P channel input JGETs would have to be fabricated from anti-matter.

The single-ended Class A output stage is "second harmonicâ€￾ in character, and it uses about half the feedback of a comparable MOSFET circuit but with half the distortion and twice the bandwidth.

The J2 power amplifier is simple, clean, and measures astonishingly well. The design is extremely reliable and will never need adjustment. It achieves a sound which is warm and relaxed, combining precision and detail without sterility. With a pair of sensibly efficient loudspeakers, it will give you a toe-tapping experience that other solid state amplifiers do not.


I love the anti-matter reference.
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Lee S
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#6

Post by Lee S »

Has there been any progress on this amplifier yet? Has he sold his first 100? Is the schematic "out there" yet? Is SemiSouth selling the JFETs yet?

I quite fancy building one of these !!
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#7

Post by Nick »

Ian mentioned this to me in a email yesterday, great minds and all that. Looks like the SJEP120R125 is obsolete now.
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#8

Post by ed »

there are loads of guys on diyaudio who have bought quantitys and are packaging them up for sale in 2s and 4s matched, teabag immediately springs to mind...

prices are ultra reasonable. I'm currently creeping up on an F2J, hence the sale of a rocky to make space....there are 2 SS jfets that currently drop in, the original is still available but there is a newer replacement...I forget the number, but think it might be R100.or R170...

checkout the group buys and pass section on diyaudio.
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