Using J201s instead of 2N5457s in an OS for bass guitar.

[lowvolt]

All apologies if this subject is tired.  I've read a few dozen things in this forum about jfets and substitutions and the like.  Much of which is over my head.  That said ...

I tried a friend's DIY Orange Squeazer with my bass recently, and I pretty much liked what I heard.  So I've taken on the GGG Orange Squeazer kit and set out to construct it.  (SIDE NOTE:  I've located and downloaded some modification specs to optimize the OS for bass guitar, and am on the fence about employing them, unless someone can give me good reason to change what I heard).  Anyhow, back to main question here, I don't have any of the 2N5457 jfets but I DO have some J201s.  What tonal affect should I expect? (darker, brighter, etc..)

I'm not a local Jedi, so I do not know how to match jfets (and it's my understanding that the OS does not require that procedure).  So if the technobabble could be kept at near-dumass levels I would appreciate it.  I know my Hammonds, and a bit about caps, but after that I'm fairly weak.  Just to say it, I'm good enough with a soldering pen so constructing the kit won't be difficult at all.  My bench skills are good, but my experience with such ~jfettage~ is low.  Not bragging you see, just eliminating the ~skill issue~ from the equation ...

In any case, since I'm not building a phase shifter (or other sensitive type circuit) it's my understanding that using unamtched jfets isn't an issue, right? 

My main question would be what should I expect to hear if I use those J201s I have instead of the called out 2N5457s?

Also, just considering something else here .... how would using J201s change the BSIAB circuit (over using the 2N5457)?  Anyone with any testing experience there?

Thank you! 

Brains at LowVolt operational levels, and the meter is bouncing at that!   

[R.G.]

I don't have any of the 2N5457 jfets but I DO have some J201s.  What tonal affect should I expect? (darker, brighter, etc..)

That's actually the wrong question. As long as the J201 works in the circuit, you'd expect no tonal change at all. The problem is that "as long as the J201 works in the circuit" thing. The J201 is an odd JFET, even for a JFET. It is a high gain, low voltage, low current thing, compared to other JFETs. So it may work OK, may not, or may distort in a funny way compared to the 5457, which is a more main line FET.

it's my understanding that using unamtched jfets isn't an issue, right? 

That is correct. The two JFETs in the OS do not need to be matched, and offer no benefits if they are.

My main question would be what should I expect to hear if I use those J201s I have instead of the called out 2N5457s?

The trick will be whether the J201s you use work in the circuit without moodifying it for the J201s specifically.

My best advice is actually some of my oldest advice. You have J201s. They may work. OK, whip them in the circuit and see. If they give ugly results, order some of the right devices. If they work, great, you're in. Turn it into a question of how long it takes to make it work rather than a win/lose.

how would using J201s change the BSIAB circuit (over using the 2N5457)?  Anyone with any testing experience there?

Same comments. Sometimes you can tinker part values to make one device work where it didn't before, but I'm guessing you don't want to do that. Try it. If it works, great. If not, order some different FETs.

[Mark Hammer]

While I doubt they are interchangeable in all contexts, I often see MPF102s used where 2N5457s are used.  You might consider them.

[Cliff Schecht]

This thread has me thinking.. I wanted to build my bass player a compressor and I think he'd appreciate the simplicity of the OS. I have three OS's built but one of them has a nasty distortion when used with humbuckers. I'm thinking that's a good candidate for debugging (to fix the distortion issues, my other two don't do this!) and modifying it for bass.

I also have a couple of original Dynacomp boards (I can point you guys to where I bought them if anyone is interested) that I want to try as a Ross/Dyna and the other setup for bass. I need to get on those, they've been sitting on the bench for too long.

I really only use the J201 when a schematic calls for one. I don't have a lot of them. I do, OTOH, have a few hundred MPF102s and 2N5457s, both of which I have interchanged with no discernible difference. I would use one of those two if you have them. RadioShack I think even carries MPF102s and if not, I could be bothered to send you a few in the mail .

[R.G.]

Cliff, watch the Idss. I don't remember the actual current setting for the JFET used in setting up the bias source, but the largest Idss for a J201 is 1ma. Typical is much smaller. There may not be enough Idss for it. It's worth checking.