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The problem with using a 1N4001 (or 4148 or whatever) is that its turn on threshold voltage is much lower than a 12v zener, so if you drive it with a hot signal, it may get some weird clipping from the diode. Otherwise, it doesn't really make any difference. Its purpose is to protect the Gate of the MOSFET from static electricity that can kill it. You could also use a different MOSFET type, like the BS170KL that has protection diodes built in.

on the early versions of the SHO there are two 4148 diodes. the second one going from C1 to 9v. what is it for?
Oh yeah and the transistors blew anyway, so he changed the design.

The point of all these diode protection schemes is to limit the gate-to-source voltage to a safe level (typically less than 12v). Diodes to ground or the supplies work as long as the diode + supply voltage is below this limit. I prefer a lowish voltage zener (~6v) from gate to source (plus a source resistor) because it never messes with the bias but is still safe at all operating points and supply voltages. Some people use LEDs but these have higher capacitance than Zeners and therefore will be less immune to static or transients compared to a Zener. But either will work as long as the diode capacitance is less than the gate-source capacitance (only a few pF).

is there a way to have the pedal be unity volume with the pot at zero? mine has a volume boost.

any help? is this how its designed? If so thtas cool, just wondering if I can make the bypass and on signal (pot at zero) the same volume.

sevenisthenumber wrote:any help? is this how its designed?

nope. i don't think so.

sevenisthenumber wrote:any help? is this how its designed? If so thtas cool, just wondering if I can make the bypass and on signal (pot at zero) the same volume.

I just placed a trimmer on the output, it acts as a volume inside.

Seiche wrote:

sevenisthenumber wrote:any help? is this how its designed?

nope. i don't think so.

The gain equation is (roughly) Rf/Ri where Rf is the parallel combination of the two 2.2M resistors, and Ri is the setting of the gain control.

Minimum gain is 1.1, or 10% louder than unity.


A couple solutions:
1) add 100k in series with the input. This will increase input Z slightly and reduce minimum gain to almost exactly 1, but also reduce maximum gain.
2) change the 2.2M resistors to 2.0M. This will very slightly reduce input Z and maximum gain.

Note the gain is actually inverting so put a minus sign in front of those numbers to be more correct.

ah i see. i guess mine has a tolerance on the gain control.

how noticeable is a gain increase of 10%? Is 10% louder really the correct description with the hearing being logarithmic? This always confuses me.

Good point. 10% increase in gain is 20*log(1.1Vout/1Vin) or about 0.8 dBV. Doesn't seem like much but don't forget it has to be amplified by a power amp before hitting the speakers and finally your ears, so that small increase in dBV becomes a bigger change in dB(SPL).

Is the value of the last cap (10uF) crucial? Can i use 3u3 as a sub or do i really need it to be 10uF.? Tnx

dorothegreat wrote:Is the value of the last cap (10uF) crucial? Can i use 3u3 as a sub or do i really need it to be 10uF.? Tnx

It will not explode -- probably... Try it and find out, but most of all -- please report back.
I don't know anything about electronics, but I could knock you dead with terms like "standard coupling cap value". Somebody else might chime in and explain, but there is no learning experience like a thoughtful experiment.

You can use 3u3 as a sub.

C2/R4 forms a high-pass filter. So changing either value changes the cutoff frequency of the filter.

However, in this case, I doubt you will be able to hear any difference. With 10u/100K, the cutoff is 0.16Hz, and with 3u3/100K it is 0.48Hz. I don't think humans can hear down that low, so you're fine to sub the value you have on hand. Anything down to about 0.1uF is going to sound almost identical to human ears.

finally finished this one. my rig is currently on a place where we are practicing so can't try this one out until tomorrow.



output cap are 3u3 and 1u in parallel. my voltage are as follows:
D: 7.55v
G: 1.56v
S: 0.00v

from a 1spot measured with 9.44v. seiche posted his voltages which are the only ones that I can find. comparing his and my voltage readings, it seems to that they are far from each other.

Seiche wrote:Okay I went ahead and measured the voltages to ground on the BS170s on both CNOs.
on both sides i get (top to bottom: d-g-s):
-4.5 V
-2.2 V
0 V

I made sure there is a cable...

BTW as i don't have any 5k1 res, I used 2 10k res in parallel with a reading of 4k80.

yeah those voltages are probably wrong, as i wrote them down before fixing my build (which didn't work right). You had me go back read my posts from 1.5 years ago, thanks
I was so naive... Thanks for putting up with me y'all.

My CNO is disassembled so I can't take voltages now. Sorry.

Edit: Alright i remembered that i still have a functioning SHO clone and the CNO is basicallly the SHO on full with a pregain control. My voltages on full blast are on par with what you wrote down. So it's pretty likely yours will work as advertised

It's not working as it should be, it gives out a low volume splutters sound. Funny thing is that it passes signal even without power

I've been a massive fan of the SHO for years and now I've just built my first CNO for a buddy who couldn't deal with the crackle. It's awesome! Nicely done Soul Sonic :0)

Why not like this, to use 10k pot for BOOST in parallel with 10k resistor? Thus the crackle will be more gentle, and all the other aspects of the circuit will remain the same? I don't have a breadboard at hand right now, but if anyone's willing to try this, please do.

Here the PCB-layout for "Crackle Not Okay" Circuit: Ready-to-Print PDF-files: Gerber files and drill file:

Forgot the SprintLayout 6.0 file: