Orange Sunshine build squeals when guitar's volume is turned all the way down.

[Nocaster Cat]

Title says it all, my Orange Sunshine starts to squeal whenever I turn the guitar's volume knob all the way down. I'm using BC109's in the build and no substitutions except for a 22uf instead of the 10uf (didn't care for the way the 10uf sounded). Where did I go wrong? Are the transistor gains too high? Bad grounding in the guitar? Thanks!

[GibsonGM]

Hi Nocaster.

This surprises you....how?  LOL.   I mean, perhaps there's an error somewhere, we can try to figure that out, but a high-gain circuit is going to feed back.  It amplifies anything and everything that is fed to it, and noise is always present.  The act of turning down the guitar 'tunes' the input path, and maybe you have a set of circumstances that works just right to drive it into feedback at that point.  Any RF or other noise in the room is amplified over and over...

First -  is it in an enclosure?  Which is grounded?  We'll assume it is.

Are you running it very 'dirty' when it squeals?  Or will it do it with the fuzz turned down, too? If turned down, that would mean a problem.  Cranked, probably no problem.

Does the squeal change when you walk away from it w/the guitar?  Or move it and guitar away from the amp? 

Do you plan to turn your axe down and have the pedal on as a matter of how you play?  If that was all my fuzz was doing, I'd be ok with it....it probably does, but I turn it off if things are going to be quiet....

All things being properly built, MAYBE this could be helped by placing a small value cap from the input to ground, starting with 100pF and working up to maybe 1nF.   Might tame it a bit, could break the feedback path, but high gain circuits just oscillate as a matter of course.   You could try it, and if it stops the squeal without changing your tone, great!   Let us know....

[pinkjimiphoton]

check your grounding like RG always says to do too. shoud be zero resistance to ground at every ground point.
also, check for cold solder joints and bridges between input and output, sometimes the tiniest hair of a wire or solder whisker can create a feedback loop as well.

i have a fuzzface i dearly love. but in some rooms, it becomes a tuneable oscillator when i turn the guitar all the way down. only sometimes. and it can be with any guitar. sometimes. can be maddening to sort out, but if ya take mike's suggestions and go over all your work, 99% of the time you'll have an "aha!!!" moment where ya find ya did something you didn't even physically think could be possible in this dimension of the space time continuum.

[duck_arse]

as we don't have a circuit to gaze upon, does your build have any supply filtering/caps?

[pinkjimiphoton]

as we don't have a circuit to gaze upon, does your build have any supply filtering/caps?

+1000000 like ALWAYS.
that could explain it. a lot of times schematics just show the circuit without the power supply.
i tend to like a small series resistor in line from the b+.... say, 47-100-220 ohms. i'm not super anal about it myself, but it helps to filter some power supply noise out. like... battery > 100r>circuit. but it's better if where the 100r terminates and the circuit begins to add a 10-100uf cap with + to that node and negative to ground. that will help smooth the supply and decouple it (i think. i'm far from an EE). i usually will also add a smallish cap (ceramic is fine) of around 47 to 470pf to ground in parallel with the bigger cap. experiment with the values a little to find one that just eliminates rfi and squeals etc. to my ear, the smaller the better usually. the combo of resistor and caps will also form a low pass filter that should shunt a lot of noise to ground.
don't use solid core wire, it tends to be microphonic and is a bitch when it breaks somewhere, and believe me, it WILL, i do use it in some circumstances, but regular stranded wire is a little capacitant <<new word?>> and will also help keep rfi down.

i think beavis's site is up again, it has some cool ideas for filtered power supplies, including one you can build into it's own pedal. you can just take the same idea and apply it to the circuit you built. you can often add the peripherals right to your power jack... put the hot and ground of the two caps to their respective terminals on the power supply jack, and run the resistor from the b+ node right to the power in on the existing board. as long as ya keep the wires short, you should be fine.
but first check your grounds.
hope this helps ya get back to making funky sounds and obscene noises soon

[Nocaster Cat]

Hi Nocaster.

This surprises you....how?  LOL.   I mean, perhaps there's an error somewhere, we can try to figure that out, but a high-gain circuit is going to feed back.  It amplifies anything and everything that is fed to it, and noise is always present.  The act of turning down the guitar 'tunes' the input path, and maybe you have a set of circumstances that works just right to drive it into feedback at that point.  Any RF or other noise in the room is amplified over and over...

First -  is it in an enclosure?  Which is grounded?  We'll assume it is.

YES.

Are you running it very 'dirty' when it squeals?  Or will it do it with the fuzz turned down, too? If turned down, that would mean a problem.  Cranked, probably no problem.

IT IS A FIXED FUZZ (SEE SCHEMATIC BELOW).

Does the squeal change when you walk away from it w/the guitar?  Or move it and guitar away from the amp? 

YES. LOCATION AND/OR PROXIMITY TO THE AMP MAKES NO DIFFERENCE.

Do you plan to turn your axe down and have the pedal on as a matter of how you play?  If that was all my fuzz was doing, I'd be ok with it....it probably does, but I turn it off if things are going to be quiet....

IT'S MORE A MATTER OF SOLVING THE ISSUE.

All things being properly built, MAYBE this could be helped by placing a small value cap from the input to ground, starting with 100pF and working up to maybe 1nF.   Might tame it a bit, could break the feedback path, but high gain circuits just oscillate as a matter of course.   You could try it, and if it stops the squeal without changing your tone, great!   Let us know....

UNFORTUNATELY THAT MADE NO DIFFERENCE AT ALL.

To answer some other questions...

- There is power filtering.
- Everything is grounded.
- The noise starts to disappear as I decrease the gain of the transistors.
- Here is the schematic.



Thanks!

[GibsonGM]

Sure, we've all built Ol' Orange, LOL.   If you absolutely can't stand it, maybe it's time to start changing transistors. Try ones with lower gain.  As you see, the original weren't what you typically use today. 

In my experience, many fuzzes do this.   It's really not 'an issue', it is a side-effect of what we're doing to those transistors, LOL.  Small move from amplifying to oscillating.   You have changed some parameters when you turn down the vol. pot.  Perhaps a small value resistor on the fuzz input could help...start with 100R, go up to 470, 1K.....I don't know at what point you will start to change from "this is the original fuzz, yay!" to "now it is something modded", though.  You change input Z when doing this, and the fuzz works with your pickups to get that 'original sound'.

In summary - if built properly, with good construction practices...it's just a fuzz.  This is what they do.  You can also try shielded input cable, and check that any components aren't coupling to others, but it may not help.    Yes, of anything, lower gain transistors will have the most effect.

[PRR]

Try adding like 5K in series with the 0.1u input cap.

This does shave some hair off the orange. But it keeps the input node from going to ZERO resistance.

What I think is happening: Q2 E against 10uFd is a high-cut and a phase shift. 22K against 0.1uFd is another high-cut and phase shift. Any little added phase shift, with this high gain (to make fuzz) becomes an Oscillator. Resistance in guitar Vol control damps the oscillation. Full-down zero resistance puts you just over the threshold for oscillation.