# J201 sub for a 2n5457?



## Dan0h (Oct 8, 2021)

Wrapping up the Pharmacist build and wondering if I can use J201s as a sub for the 2n5457s. 

Thank you build gurus.


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## Big Monk (Oct 8, 2021)

My immediate response would be no. J201, on average, will have much more gain than 2N5457. Here are values from the RoG "Fetzer Valve" article:





I'm not sure what the potential 2x boost in gain will do to the circuit.


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## Dan0h (Oct 8, 2021)

Oh wow. Good to know thank you. Might have to order some more transistors….


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## Mcknib (Oct 8, 2021)

Barry's got some not too expensive considering they're hard to get









						**JFET 2N5457 - Guaranteed Genuine - GuitarPCB
					

(1) Genuine 2N5457 JFET Transistor from my own personal collection. Hand Tested and all are in the proper range for guitar pedals.




					guitarpcb.com
				




Here's a stompville article on substitutes






						Substituting the 2N5457 – Stompville
					






					stompville.co.uk


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## BuddytheReow (Oct 8, 2021)

I see you've got sockets ready to go. I agree with the above, but I also think you should try the J201s to see if you like it if you've got them lying around. You may be surprised. Or disappointed.


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## temol (Oct 8, 2021)

We need a sticky  subject explaining this..  J201 <-> 2N5457 topic is like a boomerang


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## Dan0h (Oct 8, 2021)

Very confusing. Even on the link provided above it says “
Replacement and Equivalent:​2N4339, 2N4340, J201, 2N4338, 2N4341, 2N5458, 2N5459, NTE458​But I understand the differences in values will cause differences in sound. I can try my j201s and j112s and see if I like the sound and if not order some 5457s. 

Thank you for the awesome feedback as always!


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## Dan0h (Oct 8, 2021)

BuddytheReow said:


> I see you've got sockets ready to go. I agree with the above, but I also think you should try the J201s to see if you like it if you've got them lying around. You may be surprised. Or disappointed.


Indeed!


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## temol (Oct 8, 2021)

Dan0h said:


> But I understand the differences in values will cause differences in sound.


In some cases you can expect a different sounding circuit, sometimes not. And sometimes you'll need to change a value of the resistor/trimmer or even capacitor here and there to accomodate for the different model of the transistor. 
General rule - if it's a source followe (buffer) - you should not worry.
Gain stage - it depends. Take a look here for example.. this sould help a little bit.


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## Diynot (Oct 8, 2021)

So I posed this question in another pharmacist build thread, but didn’t get any bites, so I’ll drop it here too. what if say you have 3 of the 4 5457s and a handful of j201s if you were to substitute 1 where would you place it and what would be the effect? My theory is if it were a Q1 sub it would be like a boost into gain, but at Q4, it would be more of a boost after gain. Thoughts? I’ll admit this is def a theoretical now since I went ahead and harvested a 4th 5457 out of another build, but would still like to know


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## Dan0h (Oct 8, 2021)

Diynot said:


> So I posed this question in another pharmacist build thread, but didn’t get any bites, so I’ll drop it here too. what if say you have 3 of the 4 5457s and a handful of j201s if you were to substitute 1 where would you place it and what would be the effect? My theory is if it were a Q1 sub it would be like a boost into gain, but at Q4, it would be more of a boost after gain. Thoughts? I’ll admit this is def a theoretical now since I went ahead and harvested a 4th 5457 out of another build, but would still like to know


Great question because I have three J201s and three J112s. might just be a trail and error deal, glad I socketed.


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## Dan0h (Oct 8, 2021)

SBP has some 58s. Maybe I will try those too. 
Stomp


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## Dan0h (Oct 8, 2021)

Mcknib said:


> Barry's got some not too expensive considering they're hard to get
> 
> 
> 
> ...


Wait is the the same Barry as Barry?!


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## Mcknib (Oct 8, 2021)

Dan0h said:


> Wait is the the same Barry as Barry?!


Haha no Barry at GPCB


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## fig (Oct 8, 2021)

Mcknib said:


> Haha no Barry at GPCB


Well, I'm almost certain Barry has 2N5457s from Barry.


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## Kroars (Oct 8, 2021)

Dan0h said:


> Wrapping up the Pharmacist build and wondering if I can use J201s as a sub for the 2n5457s.
> 
> Thank you build gurus.
> View attachment 16804


Send me a message, I’ve got a bunch of SMD’s on adapter board, or just the smd whichever you prefer.


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## Dan0h (Oct 8, 2021)

Kroars said:


> Send me a message, I’ve got a bunch of SMD’s on adapter board, or just the smd whichever you prefer.


Thanks dude, I decided to give Barry a try! I’ll try my J201s first then see what the difference makes when these arrive. Barry has LM308s too! Excited


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## zgrav (Oct 8, 2021)

since you socketed the board for your transistors, feel free to experiment.  put the j201s first, then last, then try to alternate them.  it will be interesting to get your thoughts on the differences in the sounds.


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## bowanderror (Oct 8, 2021)

zgrav said:


> since you socketed the board for your transistors, feel free to experiment.  put the j201s first, then last, then try to alternate them.  it will be interesting to get your thoughts on the differences in the sounds.


This is the real answer; you won't know until you try.

Especially for builds with sockets & drain trimmers, there is no harm in trying different JFETs. For pedals, where distortion is often a desirable trait, the effect of highly variable Vp/Idss specs, headroom & biasing of different JFETs is more art than science. Of course, there are good guidelines depending on what the circuit designer was shooting for, but you're not going to blow anything up by trying something different.


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## Dan0h (Oct 9, 2021)

J201s work. Sounds full and fat at low volume. Kid is sleeping will be able to crank it tomorrow. Had an extra Mr. PedalPcb J201 smd conversion to add to my 3 iFCs. They all tested pretty close 129,132,136,139 hfe. I put them in that order. When the 5457s show up I’ll post an update.


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## bowanderror (Oct 11, 2021)

Dan0h said:


> Had an extra Mr. PedalPcb J201 smd conversion to add to my 3 iFCs. They all tested pretty close 129,132,136,139 hfe.


JFETs shouldn't have an hFE value, what did you test them with?


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## Dan0h (Oct 11, 2021)

bowanderror said:


> JFETs shouldn't have an hFE value, what did you test them with?


Maybe I miss read the value and thought it said hfe


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## bowanderror (Oct 11, 2021)

Dan0h said:


> Maybe I miss read the value and thought it said hfe


Oh you're talking about the PNPs, not the JFETs. You're good then.


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## Dan0h (Oct 11, 2021)

bowanderror said:


> Oh you're talking about the PNPs, not the JFETs. You're good then.


No I was referring to the j201s. My meter gave me those readings for each one but I will have to re-test to see what the word was next to the #. I just assumed it was hfe because that’s where the hfe # showed for my other transistors.


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## bowanderror (Oct 11, 2021)

Dan0h said:


> No I was referring to the j201s. My meter gave me those readings for each one but I will have to re-test to see what the word was next to the #. I just assumed it was hfe because that’s where the hfe # showed for my other transistors.


For JFETs, it should say something like "JFET N-Ch" at the top, and likely Id or Vg for measured values. If you're lucky, you'll get Vgs(off) and Idss values, and maybe even Gfs.


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## Dan0h (Oct 11, 2021)

bowanderror said:


> For JFETs, it should say something like "JFET N-Ch" at the top, and likely Id or Vg for measured values. If you're lucky, you'll get Vgs(off) and Idss values, and maybe even Gfs.


Thank you for the info. The 5457s should be arriving soon, when I swap them I will retest the J201s. They came from mouser and the fourth one from Mr. PedalPCB so i know they are legit 201s. But now I want to know what that number was referring to.


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## Dan0h (Oct 11, 2021)

From a different thread it sounds like this meter is garbage at reading JFETS. Looks like the cheap tester from Amazon is just a cheap tester from Amazon. Pretty sure it did a good job on my PNPs though.


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## temol (Oct 11, 2021)

Dan0h said:


> From a different thread it sounds like this meter is garbage at reading JFETS. Looks like the cheap tester from Amazon is just a cheap tester from Amazon. Pretty sure it did a good job on my PNPs though.


bingo...


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## Dan0h (Oct 12, 2021)

Dan0h said:


> Wait is the the same Barry as Barry?!





Mcknib said:


> Barry's got some not too expensive considering they're hard to get
> 
> 
> 
> ...


Not only is Barry a fast shipper, he included bonus in the bag! Kudos to you Barry. Now to the awesome news. Absolutely find and use the 5457s for this build. NIGHT and DAY difference in the way this pedal reacts to the guitar and the sound it produces. J201s sound good, but the 5457s sound right!


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