JFET options for buffers

iamjackslackof

Well-known member
Hi all,

I'm working on designing a looper with buffered outputs, as well as adding buffers to more of my pedals.

Most buffers I've seen that use JFETs use J201s. As I understand it, JFETs are used because of their low output impedance. Since this is a property of most/all JFETs, does it matter which JFET I use? In other words, what are good alternatives to J201s, and why? I'm not nearly as familiar with JFET properties the way I am with BJTs, so I don't know how to evaluate what JFETs will work. Specifically I'm talking about the PPCB JFET buffer.

Thanks!
 
I mostly use 2N5457 and 2SK30 for input buffers. J201s are, as far as I understand from ongoing discussions in certain pedal building groups, maybe not ideal as they distort rather early, making them a good option for JFET based drive pedals but less so for really clean applications such as buffers.

Just be careful with through hole JFETs these days. Many fakes and off-spec ones around. Your best option is using SMD JFETs.
 
Thanks @jesuscrisp . Do you have a go-to for SMD JFETs? I'm planning on switching to them exclusively to avoid getting burned. Also is 2SK30 not a MOSFET? I'm still not super clear on the different uses for each, and haven't seen a MOSFET used in a buffer.
 
MMBF5457 is the equivalent to 2N5457.

2SK30 is a JFET. But mosfets can also be used as buffers, just for some reason they aren't usually. They should have even higher input impedance than jfets iirc.
 
I believe mosfets aren't used as buffers as often because they are noisier. Also 2sk208 is the SMT equivalent of the 2sk30. If you don't want any chance of getting burned I'd order from mouser or digikey unless you're in a country that doesn't have access to them.
 
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