Noise in last 10% fuzz

[Marbles]

Hey there!

I build a box of hall a while back with a x-fuzz after it.. It gave a great wall of sound, it was a birthday gift for a friend.
A friend of him liked it a lot, and asked me to build it for him too (only money for parts, i'm not in business ,it's great to gain experience and try harder) . Could not remember how I did it the first time though.

Everything works, except the last 10% of the fuzz gives a high pitched noise. The fuzz sounds nice and over the top at that last part though.. would like to use that if that would be possible.

I of course used the search function, and found some (recent) post about the huminator. That didn't sound like me though. I also read that high gain circuits could be noisy. Couldn't find a solution though..

Do I have options? I think maybe changing a cap could filter out some high noise?
Or adding a resistor to the pot to not being able to turn it all open, but that would mean I'd lose the last 10%?

(If these options don't make sense, please tell me, I'm still learning :D )



What I also forgot to mention: I have the fuzz connected with a DPDT switch (3PDT to Reverb, reverb output to DPDT and DPDT to output 3PDT) . The circuit itself is grounded, so it's not a grounding problem, right? The reason I'm asking this, is because the more fuzz I dial in, I can tap on the potmeters and it affects the sound (hear tapping in my amp). Though I use a voodoolab 2 plus, I have had more grounding issues with pedals, I think it could be the power in my house.


If someone could chime in, please do! :)

[Beaker]

Sounds like you have a microphonic pot - yes it can happen. Your wire routing may also be an issue, so try to keep 9V power wires well separated from your signal wires.

[alex.s]

The noisy pot sure sound dodgy, though the high pitch noise (possibly oscillation) might be there for other reasons, as can happen with high gain circuits. If swapping the pot doesn't solve it you could perhaps try the old trick of putting a little cap (47p is a good starting point) between Collector and Base of Q2 (Q1 is already catered for in the X Fuzz, having that 100p cap).

To be fair a lot of the distortion comes from the clipping, so I put the noise more down to the pot than the gain as the truth might be it isn't 'technically' necessarily such a high gain build, but I'll let those who can do the maths say that for sure, or otherwise...! :P

[Marbles]

Thanks for the replies guys!
This will be the last time I will build something without a testrig, learned my lesson. My wiring is not that clean yet.. Switching out a pot will be a challenge, but apparently the most likely culprit. So that's first on the list.
I must admit I have had this before in other builds though. Like the triple wreck, noisy in the last part too. Like a really high, almost unhearable peeeeeep. Plus, just very noisy.

The power wires do touch some wires that go to the fuzz put, but the input and output are not that close...

I will change the pot and get back to you guys!

[Beaker]

If you are using a power supply, then that may be the culprit - try using a battery and see if the noise goes away.

It's always worth using shielded cable for input and output on high gain pedals.

I use Van Damme two core plus shield install cable like this:

http://www.ebay.co.uk/itm/Van-Damme-Pro-Grade-Classic-XKE-1-Pair-Cable-10-colours-/141667553687?pt=LH_DefaultDomain_3&var=&hash=item20fc0b5197

It can really help cut down noise or taxi radios!

[Marbles]

So.. I changed the pot and moved the power wires away from the output wire it was close too.. Unfortunately, no luck.

I recorded the noise, maybe you guys can say: Yes, that's definitely this or that. I messed with the volume as well, in combination things can get like an old radio :(


https://www.youtube.com/watch?v=d7QyqjNYTFs

[Marbles]

Forgot to mention in my last comment:

I tried a battery, but had the same problem unfortunately.

Thanks for the tip using shielded cables. I will order some and start using them, it can never hurt.
Could the noise in the video come fro non shielded cables?

Also, if I use the cap for the transistor, where would I solder that exactly on the board? Would that change any of the characteristics?


Thanks in advance!

[Marbles]

Shielded cables will not be here in time unfortunately :(

What I did notice: At a quarter of the volume it's already past unity gain. I listened to the fuzz again, and 80% is acceptable enough. The guy is not that wild of a fuzz guy.

How can I wire the pots so that the last percentage of the pot is not used anymore?

Or if that would work: The cap soldered to the second transistor as suggested, how do I do that?

Sorry for the noob questions, but I really have no idea..

[Travis]

You could run a resistor in series with volume lug 3 or volume lug 2.

I would probably start with a 470Ω or 1K resistor and gradually increase from there until the noise is gone

[Marbles]

Thanks for your quick reply!

So.. does that mean I have to solder the resistor from lug 2 to 3?

[Travis]

No basically the resistor is going in between the volume 3 wire and the actual volume 3 lug

Or you could put it between volume 2 and output

[Travis]

Of course you could use something like a 20K trimmer used as a variable resistor to tune out the noise without having to swap resistors

[Marbles]

That's a great Idea! Thanks!

[Marbles]

Tried it with the fuzz knob, cause that one is noisy at low volume as well (the last 10%) but it didn't have any effect :(

[Travis]

Sorry, for some reason I thought this was a one knobber but obviously it's not.

So you did what I said but with the pregain pot right? How much resistance did you try?

[Travis]

Since you say the noise happens in the last 10% of the pot, and the pot is 1M, then I guess you'll need a bigger resistor. 10% of 1M is 100K, so try a 100K resistor. If that doesn't do it just keep going higher gradually

[Marbles]

Hey!

Ehm, yes, I did try a very low one. I soldered a 10k trimmer. The other values I had were 5 or 100.
I will try the 100 for sure! How will that affect the tone? Does it mean that I can't use that last 10% anymore? If that's what I have to sacrifice for a normal working pedal, it's fine. Better than the squeeling.

The volume is the same though. If I put that open full, it's going to do crazy radio squeels as well. The thing is, it's so super loud. The reverb is just above unity. But the fuzz, man, at 50% it's so loud already.

I have the reverb first. The reverb output goes to the middle lug of a dpdt switch. The other middle goes as output to the 3pdt switch. Upper 2 lugs of the dpdt are connected. The bottom 2 are input and output of the fuzz circuit. That is wired correct right? No need to ground this extra in some way?

The reason I ask is: I have boxed 2 effects in one before, and they almost all had problems with noise. Just so I don't miss anything.


I'm sorry for bothering you guys with all this. I've spent 6 nights after work soldering-resoldering for hours and still haven't fixed it. I'll try the resistor and the shielded wiring if they come in.

I'm cleaning up my wiring now as well, it's just very hard. I separated the signal and power wires as much as I could, am shortening them as much as possible. But sometimes it's inevitable, especially with 2 power wires coming from different circuits. A power wire will have to cross a signal line sometime. But only once. Plus it has a belton brick, so it's a lot of wires anyway.

I'm just afraid it's not going to work, the 2 pedals in a box, or not for me, yet. Oh well, powering through ;)

[Beaker]

"But sometimes it's inevitable, especially with 2 power wires coming from different circuits. A power wire will have to cross a signal line sometime. But only once."

You have the right idea with this Marbles. If a power wire has to cross a signal wire, try to cross it at 90 degrees - just like a road brigde going over a Dutch canal. What you don't want is the "road" running alongside the "canal", as the traffic noise from the power wire "road", will be heard on the signal wire "canal".

[Marbles]

Ah, great! Since I'm Dutch, that's something I should be able to do!  

[Beaker]

Yes, that's why I used that comparison - I thought it might help. Ground wires act like a noise fence, just like you see at the side of motorways when there are houses nearby. The fence keeps the traffic noise down, and the ground wire keeps the noise from the power wire from your signal wires. This is why shielded wire can work so well if you cannot avoid power wires running near signal wires.