how did you get on with this ?
especially interested in the 1:1 transformer in place of the bulbs,looking at the resistor route or the tranny.
and finally read the whole thread and cut and pasted relevant posts,so hopefully no more basic questions to Mike 🙂
As you know I can´t stop....
waiting for my 300W 110V bulbs coming from UK and fairly expensive (10 Pound one, does anybody know a cheaper source delivering to Germany?)
a friend borrowed me for a longer time a real First Watt J2......!😀😀
so I could hear it against my J2 clone tries and the SIT with CCS number D of Mike suggestions (IXYS depletion mode MOSFET).
First impression, .... the J2 clone tries sounded all much brighter and had less room. The J2 has a lovely darker atmosphere and very much room around the speakers. Some people say they miss some directness or presence in the medium area.....surely a matter of taste.
I tried many variations in my clones, I did not get the sound of Nelson.....
(more inductive source resistors, less inductive source resistors, very close matched J74 with 8 and 10 mA Idss, more current up to 2 A, feedback cap from 10 to 20pF)
I suppose the R125 Nelson uses has more influence on the sound than supposed, I used R100.
Nevertheless all clone tries had at least a bit more grip in the medium area..
Next try was....
why not trying a SSR100 instead of the SIT SK82, some people like pentodes more....
of course I had to implement a source resistor of about 0R5, otherwise the gain was to high (around 30x)....
first hearing was not bad....
with the Mu solution I described in this thread there was a big fat bass and sparkling highs with my Lowther/Tone Tubby (maybe this version of a current amp had a bigger output impedance)), the medium area was a bit strained...
the R100 with the IXYS depletion mode MOSFET as CCS ( so simple to build), the sound was no more so spectacular in the bass and the highs, but the medium area was fine....more fine....
and now I heard this solution again against the SIT with IXYS depletion mode MOSFET
the winner was the SIT!
and I heard the original J2 against the SIT with IXYS depletion mode MOSFET and the J2 was a tough opponent but in the sum I preferred the SIT sound.
so you see we have even in the CCS version, easy to realize, a very very very fine amp!😀😀😀😀
Thanks Mike
and thanks Nelson in this case especially for the Zen Story, that seems to be the foundation of this all.....
waiting for my 300W 110V bulbs coming from UK and fairly expensive (10 Pound one, does anybody know a cheaper source delivering to Germany?)
a friend borrowed me for a longer time a real First Watt J2......!😀😀
so I could hear it against my J2 clone tries and the SIT with CCS number D of Mike suggestions (IXYS depletion mode MOSFET).
First impression, .... the J2 clone tries sounded all much brighter and had less room. The J2 has a lovely darker atmosphere and very much room around the speakers. Some people say they miss some directness or presence in the medium area.....surely a matter of taste.
I tried many variations in my clones, I did not get the sound of Nelson.....
(more inductive source resistors, less inductive source resistors, very close matched J74 with 8 and 10 mA Idss, more current up to 2 A, feedback cap from 10 to 20pF)
I suppose the R125 Nelson uses has more influence on the sound than supposed, I used R100.
Nevertheless all clone tries had at least a bit more grip in the medium area..
Next try was....
why not trying a SSR100 instead of the SIT SK82, some people like pentodes more....
of course I had to implement a source resistor of about 0R5, otherwise the gain was to high (around 30x)....
first hearing was not bad....
with the Mu solution I described in this thread there was a big fat bass and sparkling highs with my Lowther/Tone Tubby (maybe this version of a current amp had a bigger output impedance)), the medium area was a bit strained...
the R100 with the IXYS depletion mode MOSFET as CCS ( so simple to build), the sound was no more so spectacular in the bass and the highs, but the medium area was fine....more fine....
and now I heard this solution again against the SIT with IXYS depletion mode MOSFET
the winner was the SIT!
and I heard the original J2 against the SIT with IXYS depletion mode MOSFET and the J2 was a tough opponent but in the sum I preferred the SIT sound.
so you see we have even in the CCS version, easy to realize, a very very very fine amp!😀😀😀😀
Thanks Mike
and thanks Nelson in this case especially for the Zen Story, that seems to be the foundation of this all.....
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been measuring Id and Vds with V+ @ 52v,speakers measure 13 ohm(16ohm)was only monitoring Vds with a digital meter,nice to know the current values now.
2.45A = 21.8v
2.5A = 20.5v
2.55 = 19.6v
2.6 = 17.7v
2.65 = 16.3v
2.7 = 15.5v
Sounding pretty good at 2.5A
2.45A = 21.8v
2.5A = 20.5v
2.55 = 19.6v
2.6 = 17.7v
2.65 = 16.3v
2.7 = 15.5v
Sounding pretty good at 2.5A
Hi Generg,
Talking about the SemiSouth R100 & R125 if you or any one else is interested in the R125 a friend of mine has some that he would be willing to sell (we have more then we need) and Mike can vouch for their authenticity...
We got them to build Mikes all JFET 'Amazing FET Circlotron'
The R125 has lower capacitance and nearly twice the Transconductance of the R100...
Peter
Talking about the SemiSouth R100 & R125 if you or any one else is interested in the R125 a friend of mine has some that he would be willing to sell (we have more then we need) and Mike can vouch for their authenticity...
We got them to build Mikes all JFET 'Amazing FET Circlotron'
The R125 has lower capacitance and nearly twice the Transconductance of the R100...
Peter
Here in Canada they are 3 Pounds per bulb but then there is shipping to Germany.
Generg. Drop me a PM and we'll see where it goes.
Regards,
Dan 🙂
My data is that the differences are marginal. I treat them as pretty much the
same part.
😎
Thanks 😎
One hope less to explain the sound difference......🙁
But I do not give up! The original J2 is the reference for my experiments also concerning the SIT! 🙂
Sorry for being slightly off topic, but the problem with builds is often to have a good reference!
One hope less to explain the sound difference......🙁
But I do not give up! The original J2 is the reference for my experiments also concerning the SIT! 🙂
Sorry for being slightly off topic, but the problem with builds is often to have a good reference!
nope in J2
in simple SIT amp , certainly
(D in name means depletion)
or you prefer to send them for proper disposal ?
in simple SIT amp , certainly
(D in name means depletion)
or you prefer to send them for proper disposal ?
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These were earlier editions of the R085. They generally require a negative
bias on the Gate, as in the example of the De-lite.
😎
Attachments
I broke my wrist (badly) six weeks ago, and haven't finished the second one. I may get the OK to stop wearing the brace Thursday afternoon when I see the surgeon again. If so, I should be able to work on the second one this weekend, which is a long weekend in the US.
Roscoe
