FirstWatt J2

[qusp]

what is everyone making the big deal about for in here? i'm looking for the atrocity, Nelson has welcomed us to try to exercise the grey matter and make the amp, but simply does not publish an official schematic, so that nobody can label a fake the real thing, or produce one without doing some hard work. in general fakers want something for nothing, they do not want to work for it. but all these people in here posting as if something imminent and terrible is about to happen that will change and soil us forever......

this is not the first amp that Nelson has designed that is replicated, or interpreted here and it will not be the last, the whole part of the forum is devoted to interpreting, mixing and matching his designs, applying his philosophies to other designs and the learning that goes with that; he actively encourages it. we can only respect his wishes to not clone his product and give it away or sell it, but at least to me, his own words seem to welcome us to try and make it for ourselves for our own enjoyment

[NYCOne]

Originally Posted by HVfanatic

Old schematic used, needs correct values...

In my opinion a possible topology...

Dirk

I built an amp very close to this design. My front side is essentially exactly the same.

On the back side, I used 15K off the V+ (instead of your parallel 3K9). I also used a CNY17-4 for biasing. I used parallel 0R68 in the bottom half of the circuit where you have parallel 0R47.

The amp works. I would publish the schematic, but it was given to me by another forum member who's already said they intend to publish it.

I'm eager for the author to publish the schematic, because he and I have had different experiences in biasing. His published numbers are fantastic.

[HVfanatic]

I used a picture of another member, just put in my changes. Values have no meaning - I just want to discuss topology...

Regs, Dirk

[Tazzz]

Originally Posted by HVfanatic

I used a picture of another member, just put in my changes. Values have no meaning - I just want to discuss topology...

Regs, Dirk

If you go over to tubecad.com Joe Broskie have several articles detailing what he calls "impedance multipliers" which essentially is the exact same thing as the outputstage of the J2.

The thing is although 2.5V (tl431) would be about the right voltage needed for biasing there is to my knowledge no 6-pin 431 available from any vendor, it is however the common package for optocouplers.

[HVfanatic]

Don't care about number of legs... ;-)))

Maybe these?

##20x TL431 Präzis. Spannungsreferenz 2.5V 1% ?0,111/St | eBay

[HVfanatic]

Hi Tazzz,

can you post your solution?

Regs, Dirk

[Tazzz]

I have posted a short description here:

FirstWatt J2

[flg]

Originally Posted by Tazzz

...The thing is although 2.5V (tl431) would be about the right voltage needed for biasing there is to my knowledge no 6-pin 431 available from any vendor, ...

I seem to remember there was one? And a 1,25V version also.