Can anyone find J201

fig said:
Yes, looks like almost exactly half there.
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I think in thier Fetzer writeup RoG showed the average factor of gain for the J201 was 4.8 and for the 2N2457 it was 2.

I’m planning a Marshall FET preamp made with 2N2457 to go into the clean side of my Marshall MS2 battery amp. So this discussion is timely.
 
fig said:
I guess it's not a question if it will work or not, but rather how well will it perform the task?

Do you know the target gain @Big Monk ?

@temol isway more knowledgable than I (y)
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Judging by RoG’s own comments on Thunderbird and Thor, J201 had entirely too much gain to ape the JTM45/Early Plexi tone using thier tubes to FET conversions.

Looking at thier chart, it seemed the 2n2457 had enough gain relative to the J201 to do the trick but I’m not all that experienced with FETs. The plan was the typical 2 Volume, TMB, presence and Feedback controls with a total of 5 gain stages.
 
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Big Monk said:
with a total of 5 gain stages.
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Maybe that's the key?

I put together a battery preamp board + power amp board. They run on a Dewalt 20Vmax, and I had it in a little tweed 1x8 combo...(think I have a pic). The preamp is a tube screamer + EQ, and the power amp is one similar to the one PedalPCB has had on order for awhile. It's pretty quiet considering the wiring is spaghetti.

If you think about it, let me know how it goes. i Your project sounds pretty cool.
 
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bzdunowski said:
I have been looking for awhile but I am sure I dont know a lot of the sites to look at. If anyone can give me a link to someone who has these in stock I would appreciate it

www.taydaelectronics.com

J201 JFET N-Channel Amplifier Transistor

National - Get It Fast - Same Day Shipping
www.taydaelectronics.com www.taydaelectronics.com
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guitarpcb.com

JFET J201 – Very Limited Supply

<h2><b>Genuine </b><b>J201 </b> JFET Transistor from my own personal collection.</h2> <span style="color: #ff0000;">Batch tested with a proper (JFET exclusive) testing circuit for guaranteed results.</span>
guitarpcb.com guitarpcb.com

These are still available. You can also get the smd version soldered to a small pcb on pedalpcb
 
For the JTM type circuit you need only 2 -3 gain stages. With 5 gain stages you may end up with hi-gan circuit.
1st stage - 2N5457, no clipping, just to boost the signal.
2nd /3rd stage - J201
 
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temol said:
For the JTM type circuit you need only 2 -3 gain stages. With 5 gain stages you may end up with hi-gan circuit.
1st stage - 2N5457, no clipping, just to boost the signal.
2nd /3rd stage - J201
Click to expand...

I was going to use a tweaked version of the original RoG Thunderchief, but with tuning related to the Revised Fetzer Valve, a Fauz PI gain stage for presence and feedback, and both Normal and Bright inputs.

The Thunderchief used 5 J201 FETs but when they revised it to the Thor, there were now only 4 FETs total: 3 2N2457s and 1 J201 plus the opamp for tone shaping at the tail end. Thier comments were that the J201s had more gain potential than the cloned circuit which I assumed was the reason they changed to mostly 2N2457.

I guess I arrived at 5 2N2457s because I figured i'd match the basic topology of the Thunderchief with Tonestack, which had 5 FETs, but tweak the circuit to my tastes and per the Revised Fetzer valve article.
 
Leftovernoise said:
guitarpcb.com

JFET J201 – Very Limited Supply

<h2><b>Genuine </b><b>J201 </b> JFET Transistor from my own personal collection.</h2> <span style="color: #ff0000;">Batch tested with a proper (JFET exclusive) testing circuit for guaranteed results.</span>
guitarpcb.com guitarpcb.com

These are still available. You can also get the smd version soldered to a small pcb on pedalpcb
Click to expand...
Thank you I just ordered these from guitarpcb
 
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