Zvex Super Hard On

[frequencycentral]

I can't get this layout to print at the right size for the life of me. What are the dimensions supposed to be? Do I have to scale it down?

It's the same size as a 5 x 8 hole piece of perf, so 13mm x 20mm approx.

[quarara]

http://www.mediafire.com/file/jjhzmdmwnmt/sho.pdf
I've done a pdf file. I think I did it alright.

[frequencycentral]

I've got a SHO on the breadboard (again). This time I set up the crackle knob like a FF fuzz knob, lug 1 to source, lug 3 to ground, lug 2 to ground via a 10uF cap. No crackle. Discuss?

[cpm]

I've got a SHO on the breadboard (again). This time I set up the crackle knob like a FF fuzz knob, lug 1 to source, lug 3 to ground, lug 2 to ground via a 10uF cap. No crackle. Discuss?

you get the mosfet hiss at maximum level on all the pot range

[earthtonesaudio]

I've got a SHO on the breadboard (again). This time I set up the crackle knob like a FF fuzz knob, lug 1 to source, lug 3 to ground, lug 2 to ground via a 10uF cap. No crackle. Discuss?

Fixed bias helps keep the crackles out.

[TELEFUNKON]

I've got a SHO on the breadboard (again). This time I set up the crackle knob like a FF fuzz knob, lug 1 to source, lug 3 to ground, lug 2 to ground via a 10uF cap. No crackle. Discuss?

We don`t know how you number your lugs, but most probably you are not sweeping the DC. You most likely just sweep an AC degenerative feedback in and out of the circuit. Result: no crackle. Like in a Fuzzface and others.

[MetalGod]

I seem to recall reading ages ago that if you switch the battery voltage from the output jack, you won't have the issue of possibly blowing the mosfet in the SHO.

[Slade]

What if you let this circuit with a jumper (or a small resistor) to ground at the source and put a "level" pot at the out?

[soggybag]

There was a post by Z somewhere where he talked about the cap to ground off the source. This removes the crackle. But he said it cut the max gain by a small amount. He figured players wanted that extra gain. He gave some numbers also. I think he said he could a gain of 50 or 60 with a pot to ground. The cap reduced this.

[therecordingart]

http://www.mediafire.com/file/jjhzmdmwnmt/sho.pdf
I've done a pdf file. I think I did it alright.

I didn't end up using this. I really appreciate the help, but I ended up using a piece of vero. Your PM was completely unnecessary.

[earthtonesaudio]

I seem to recall reading ages ago that if you switch the battery voltage from the output jack, you won't have the issue of possibly blowing the mosfet in the SHO.

The amount of voltage required to blow the MOSFET is something like 20V between gate and source.  A 9V battery can't make that happen.
However, static discharge can.  It only takes a minuscule amount of current at high voltage to punch through the gate. 

The danger comes from inserting the cord.  The battery is unrelated, so it doesn't matter which jack you use.  On the other hand, if you customarily unplug to disconnect the battery, then using the output jack will help, by reducing the number of times you plug a cord into the input jack.


There is an extremely cheap thing you can do to vastly improve the ESD immunity:  add a resistor in series with the input.  It doesn't have to be large, 100 ohms should be plenty.  This will dissipate the current and protect the MOSFET.

[frequencycentral]

Vex'x own schematic, the zener goes to ground: http://www.zvex.com/module_instructions.pdf

[jacobyjd]

Interesting stuff about the blown transistor business--I haven't run into that problem. My SHO is pretty much completely stock, and I love it. I actually prefer the crackle--I've used it with a looper for some interesting noise creation to overlay with my guitar playing

[pinkphiloyd]

I just built a SHO for a friend, using my super compact layout below. Nice boost, but it does indeed crackle like grandpa's 78's. Might seem like a daft question, but why not just ground the source, remove to resistor to ground at the output, and use a pot configured as a voltage divider at the output for a volume control? Or am I missing something?

I don't know anything about electronics (though now that I've finished school I want to learn) but I can read a schematic and put stuff together.  I just don't know why it works.  Anyway, where would be a good place to slap an LED in there?  I like my pedals to glow.

[kaboom]

Hey, I have a problem, it doesn't sound.I have all grounds connected to the enclosure(I checked with a multimeter and yes, all grounds are connected). I get about 8.8v at the pad which is right to R1(source?) But then I get 0.0 v in gate and drain.What can I do?
Oh by the way, I have the positive of the c2 down, I mean, the positive of this cap is connected to the output.
What does " D G S" mean?

[El Heisenberg]

Im confused. I think the zener protection diode goes anode to ground, but frequencycentral said it goes to S. Could anyone clear this up for me?

[frequencycentral]

There's a link to Zvex's own schematic in reply #51, it does indeed go to ground. However, the AMZ Mosfet Booster and ROG Peppermill have the zener between G and S. I don't think it makes much difference, certainly none to the tone. The important thing is to protect the G.

[El Heisenberg]

Cool. Ill use a 12v zener anode to ground

[El Heisenberg]

The inventobox module SHO schem has other differences...a .01 cap and 1k series combo at the input. ...?

[earthtonesaudio]

With the zener to ground, large negative inputs could cause the diode to conduct in the forward (non-zener) direction.  Whereas with the zener to source, and the gain control NOT at maximum, there is a higher resistance path for current to flow so clipping with the same input signal will be reduced or eliminated.

Regarding the other differences, I think .01 is the standard size for the input cap on the SHO.  The 1k resistor in series with the input is not something I've seen in a Zvex pedal, but it would be beneficial to the SHO because it will reduce the chance of ESD damage significantly.  Of course the input should still be capacitively coupled, so in the final build you'd have cap+resistor in series going into the gate.