PETE CORNISH NG-2 - BIG MUFF STAGE
The first two stages of the Pete Cornish NG-2 are pretty much a Big Muff. Boost, then clip.
The Big Muff clipping stage uses a combination of a 220n capacitor and germanium diodes, with a 1n capacitor across the base and collector for filtering, and quite a high value 680 ohm resistor to ground from the emitter (this is the same as the Pete Cornish G-2). So all G-2 related mods will work here - do try it stock first, as this is a very different beast to the G-2.
FUZZ FACE STAGE
The last stage is a Fuzz Face, so you could try NPN germanium transistors. I tried it, and while it worked, I reverted back to silicon. The silicon sounded tighter, and I feel this needs a bit of tightness, as the NG-2 produces a lot of squishy fuzz when cranked. It has a real feel to it when you play - at least, I think so anyway.
PETE CORNISH NG-2 FUZZ - VERO LAYOUT
LTSPICE RESULTS
Hello, is there any chance you have the schematic for this please? I can reverse-engineer it from the vero layout, but am less likely to make a mistake than if there's a schematic already in existence. Thanks!
ReplyDeleteHello - this is it https://www.pedalpcb.com/docs/Nugget.pdf
ReplyDeleteGood luck with the build.
Hello, question here - to deliver more treble to the effect sound - should i change a C8 cap in to higher value (to block a bass ferqs on FF entry stage) or change a C13 cap value (in tone stack - i am refering to Nugget fuzz schematic)
ReplyDeleteHi Grzegorz,
DeleteI'd try changing C4 to a 470pf which is the stock value for a Big Muff. Maybe also trying leaving off C7. Reducing C8 will help, try a 100n, might even be able to go smaller. Making C13 smaller will help a little, but it is just a low pass filter, and I always start with it all the way open anyway.
I've built a couple, and I normally find them bright enough. But I guess it also depends on your rig.
Good luck with the build.
Andy
update - I tested it on LTspice. Most effective is reducing or removing C7, as well as reducing C4 to 470pf. Reducing C10 can also help.
DeleteDear Andy,
Deletemany thanks for fast reply!!
Will try all your suggestions - the reason is to brighten up a little a guitar with humbuckera (normally i use Jaguar with single coils).
I assume in final stage will end up with switch to have a brighten and "Stock" sound.
Once again - thank you! (for tip and all suggestions on this blog)
Happy to help Grzegorz, although I may not always reply as quickly as this. ;-). This might also be of interest - https://vero-p2p.blogspot.com/2021/04/pete-cornish-sort-of-modded-fuzz.html.
DeleteDear Andy,
DeleteShort feedback from addition of your tips:
- C4 to 470pf - sound appeared to be morw sharp and tight
-C7 to 470pf - wild mod but comparing to leaving of gave a more brighter sound;
C13- changed to 10n
- i have made a decision to put a bias trimpot as a pot (with 8.5k resistor- 4.7k left to much "dead space" on a pot...). Bias pot is 20k (i know you have commended 25k but 20 was the one i have got on bench).
Addition of bias was a secret key - able to dial this "dying amp" tone to massive wall of sound.
Tested with Jaguar on single coils and Dean CadiX on stock humbuckers (bridge) - with second solution gave brighter sound.
Once again - thank you for support....gonna build another ng2/ng3 box.
Have a good day!
No problem - sounds like you had fun experimenting. Glad that you got it to a place where you are happy with it.
DeleteGood afternoon Andy, i have one more question.
DeleteAfter some use - i have faced a symptoms of dying effect in a whole - manipulation with bias pot didn`t made any difference- the problem has appeared to be Q1 - which i have replaced to BC550C....the thing is that sustain pot works only in half - from 0 to 50% is silent ( ihave tried does the value has an impact on this but with 100k was the same - with 10k...like additional bias). Replacement of Q3 into BC550C did solved the issue. Question is: as sustain pot set the amount of voltage for Q3 - does the problem is with the right biasing of Q3 or Q2?
Hello - that's really unusual, as the sections operate independently. The sustain should work between 0 and 50%. It does not set voltage for Q3, as any DC is blocked by capacitors.
DeleteDo you have a multimeter to post voltages, or an audio probe to test signal flow?
Oh and I updated the layout, as there was a cut that should not have been there. It's not something that would cause the issues you mention - see note on layouts above.
DeleteI have found that guilty was C4 cap (replace during treble mod). I di not catched this issue as it shows a while after turning on of the effect (as the caps will be charged) - change from original 10nF to 100nF has solved the case.
DeleteInteresting - well glad you have it working again.
DeleteHello again,
DeleteI think i need to summarize again those mods with one certain point - this strange behaviour of effect was because of badot of transistors....yes....seems like most was with some kind of failure...i have left ot for a while...thw when new btch has arrived i have rwturn to the topic...and...all is okay...
Thanks again...mods verified!
Glad it’s working properly now - that must have been very frustrating
DeleteHello, i am very interested in this build, but this isn´t not traced, its only a asumption right? In any case, I am enough interested in this proyect to build it to test it, I take you word on the good sound it has..
ReplyDeleteHello. The schematic used is from pedalPCB - while the tracing journal was not published, I think it’s a safe bet that it’s accurate.
DeleteHi, I built one using a different layout, is it normal that bias trim is only usable in a short range?
ReplyDeleteOnly a short range seems useful, just between silence and loud hum.
Loud hum is all I get for most of the rotation. What's your experience?
Ok - something is wrong. It should be useful across the entire range.
DeleteThank you very much for the quick reply Andy, do you have a voltage chart?
DeleteI'll check voltages on LTspice and get back to you. I'm not sure what I've done with my build...
DeleteThe spice values will be close to real world values.
Here’s some voltages as a guide. This is from spice, so just use as an indication. With a 50k bias pot set to 25k
DeleteC. B. E
Q1. 5.5 0.8 0.2
Q2. 4.8 0.8 0.2
Q3. 6.8 1.2 0.5
Q4. 2.0 0.7 0.1
Q5. 2.4 2.0 1.3
Set the bias all the way to 50k
Q4. 1.8 0.7 0.05
Q5. 3.1 1.8 1.2
Do you have an audio probe? Would be good to narrow down where the problem is.
DeleteThank you Andy! Voltages seem fine, I will build a quick probe hoping to find the culprit, or make a new board altogether
DeleteAudio probes are really valuable - if you can go the next step and connect to a computer with some free oscilloscope software, even better. I use a cheap iRig connector that connects to the mic/headphone jack and this https://www.sillanumsoft.org it looks dodgy, but it works well.
Delete