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Old 17th May 2012, 09:58 PM   #1141
KASUMI is offline KASUMI  United Kingdom
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Quote:
Originally Posted by Roscoe Primrose View Post
When my K82s get here, I'll be building one kinda like fig 11, but with V+ of about 22v and a 1:1 transformer in place of the light bulbs.... I'll most likely lose C1 as well. Will report when it's up and running...

Roscoe
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.
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Old 18th May 2012, 06:11 PM   #1142
KASUMI is offline KASUMI  United Kingdom
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and finally read the whole thread and cut and pasted relevant posts,so hopefully no more basic questions to Mike
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Old 18th May 2012, 06:20 PM   #1143
generg is offline generg  Germany
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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.....
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Last edited by generg; 18th May 2012 at 06:40 PM.
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Old 18th May 2012, 08:04 PM   #1144
KASUMI is offline KASUMI  United Kingdom
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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
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Old 19th May 2012, 09:41 PM   #1145
Sven257 is offline Sven257  United States
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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
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Old 19th May 2012, 10:56 PM   #1146
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Originally Posted by Sven257 View Post
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
Isn't the R100A going to be a part of the upcoming F6?

Regards,
Dan
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Old 19th May 2012, 10:59 PM   #1147
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Quote:
Originally Posted by generg View Post
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?)
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
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Old 20th May 2012, 01:09 AM   #1148
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Originally Posted by Sven257 View Post
Mike can vouch
I can confirm I have seen the stash and was lucky enough to score a few.
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Old 20th May 2012, 02:39 AM   #1149
generg is offline generg  Germany
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Quote:
Originally Posted by Sven257 View Post
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
Oh, what a friendly offer, I will PM you....!
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Old 20th May 2012, 02:40 AM   #1150
generg is offline generg  Germany
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Quote:
Originally Posted by dantwomey View Post
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
One more friendly offer, Je suis enchantée !
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