# 2N5457 vs 2N5458



## JBoss

Looking to build the Glory Hole, and after scouring forums/and websites, a legitimate 2n5457 is pretty hard to find now. Was wondering if 2N5458 would work as a replacement or if there are any other options? I have minimal knowledge so wanted to reach out to all of you here and see if I could get some help! Thanks all!


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## temol

JBoss - you can use SMD version of the 5457 - MMBF5457. You can also use 5458 - gain of the stage with 5458 will be slightly lower than with 5457. To compensate for this you can increase value of the drain resistor from 22k to 24k. But you can also leave the original value.

T.


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## phi1

Totally agree with what temol said, just wanted to add a bit more context. For 2n5457 and J201, smd is the way to go. Don’t be tempted to buy through hole types from eBay or some other questionable source, and they will be way out of spec or just plain fake. 

See the smd conversion mini-pcb on this site (under Utility). It works for j201 or mmbf5457. It takes a little patience, but it’s very doable. (Maybe order several PCBs and jfets in case you make a mistake). 

As temol said, the 2n5458 (which you can still get legit through-hole parts) should work in this build, but it has lower gain than the 2n5457. In pedals where the jfet is clipping (providing the distortion) (example, catalinbread 5F6), this would make a big difference in sound. 

In the morning glory, *i think* the jfet is only providing volume boost at the end of the circuit, not providing extra distortion (I could be wrong as I haven’t built it). If it’s only a volume boost, 2n5458 should sound the same as the 2n5457, the max output will just be slightly lower.


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## Chuck D. Bones

Whether you use 2N5457 or 2N5458, not every one that is in-spec will work in that circuit.  That's because there is a large range for Vp aka VGS(off).  The spec for 2N5457 is -0.5V to -6.0V.  The spec for 2N5458 is -1.0V to -7.0V.  Anything over -3V and you will have zero headroom. Little or no signal gets thru unless you start fiddling R16 and R18.  There are plenty of other JFETs that will work as well.  Whatever you use, test 'em before installing.  For maximum headroom, you want something around -1.5V when using a 9V power supply.  This pedal can be run at 12V or 18V, provided the electrolytic caps are rated for it.

One more thing: if you want more gain out of the JFET stage, reduce R17.  You can go all the way down to zero if you like.  Just bear in mind that if you go far enough, Q1 will be overdriven and make more distortion.  Maybe you want that.


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## Mike McLane

Hmm?  I built the Cleaver (Keeley Katana) and it uses a 2N5458.  The thing will tear your head off with the volume knob a 9:00.  I tested it against my MXR Boost/Line Driver (20dB boost) and the MXR is very tame by comparison.  I dbl checked all of the other components and they seem to be OK.  Could it be a flakey 2n5458?  Should I try the SMD version?


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## Chuck D. Bones

Not sure I understand what you're asking here.
Do you think there is something wrong with your Cleaver?  Sounds like it's working fine to me.  What position is the switch?  How did you set the trimpots?


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## music6000

The Trimpots should be set at 1/2 the supply voltage, so around 9v at the Drain of each 2N5458
With DMM set to DC Voltage, Black probe to Ground , Red probe to Drain leg of 2N5458.
If it is Higher, it will increase Headroom & Rip Your Head off!


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## Chuck D. Bones

The maximum headroom occurs when 1/2 of the power supply voltage is dropped across the FET.


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## Mike McLane

I biased it both of then @ 9V.  I just thought that since we were talking about dodgey JFET's maybe I had cheap units that might be way out of spec.  Doesn't sound like it.  Thx.


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## music6000

Mike McLane said:


> I biased it both of then @ 9V.  I just thought that since we were talking about dodgey JFET's maybe I had cheap units that might be way out of spec.  Doesn't sound like it.  Thx.


I would change the Pot to A250K so you don't have such a rapid Gain at the beginning of the Pot.
I do this on a lot of builds that list B taper for Volume pot.


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## Chuck D. Bones

The only time I use B-taper for volume is when I plan setting it well above noon.  I wonder is using B-taper is a gimmick some pedal builders employ to make the uninformed user think their pedal is louder.


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## music6000

A good example is the original Fender Hot Rod Amps.
Too Loud at 2, Flatout at 5.
Only way around it was to make a 100k passive attenuator to go through the effects Loop & adjust it so you could control the amp better.


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