Sometime circuits squeal, sometime not

[JackSkellington]

Hi, I'm living a weird experience with a pair of my circuits I'm building.
I have on verobaord a Wooly Mammoth, it worked, but at high setting of the Fuzz and EQ I noticed got the tipical squeal coming from the power supply, usually I never have this problem. With the battery non squeal at all.
So few days later I made the place on the board to add a pair of socket pin to test a resistor or a diode in line with the 9v. I tried a 47R resistor and I apparently solved the problem, indeed, I can't hear any squeal. But using a jumper on the socket to see the difference I got none squeal! Ok, maybe in the first test I had a lot of wires connected on the breadboard, I made some experiment with socket pin on the board (to try some caps) that caused some the squeal. Fine, I don't need any resistors or diodes, and then I soldered the jumper on the 9v.

Now I built a Pharaoh Fuzz on veroboard. It really worked perfectly. in a second test to make some experiment I got the squeal! Really weird, the day before worked fine! Let me try the Wooly Mammoth. It squeals, too!. What's happening?
I tried my Triple Wreck clone, it sounds fine. My power supply should be ok.
I tried the Pharaoh Fuzz touching the DC jack and in some positions the squeal goes away. Somehow I tried another DC jack and with that Pharaoh Fuzz was ok, again. Solved! It was a bad DC jack.
Probably it will be the same things with Wooly Mammoth. Instead, with the same DC jack I tried with the Pharaoh the Wooly Mammoth squeals anyway. I tried with a 100R or with a 1N5817, but it squeals.

Someone can tell me something about all this?

[thomasha]

Squeal is normally a symptom of some undesired feedback. The component and wiring positioning is very important in this case.
When you made the changes, did you move the wiring around?
Interesting that with battery there was no squeal... in my experience with amplifiers the feedback normally comes from another stage, not from the supply, unless you are using a switched power supply. But then, it should be more like a whine...

Shielded cable for the potentiometers helps to avoid some kind of feedback, but fuzz and high gain circuits can be very sensitive. Try moving things around.

Sometimes when boxed the squeal goes away (effect of the enclosure) or when you put the board close to a ground plane (or enclosure wall) it creates a shielding effect against emitted signals.

[JackSkellington]

Wiring and component positioning is very important, I learnt it in a pair of cases during my building. An OCD with a lot of jumper wires from the board on the breadboard. I got a squeal at higher gain setting. When I put the component directly on the board the squeal is gone how I confided.
Once I built a Rat veroboard, I got an unexpected terrfying squeal (oscillating problem) at high gain settings with the bridge humbucker (some people got this issue, someon else not). I changed the layout with another I used in the past. It works perfectly.

In these last cases maybe we can call this squeal with the words whine, English is not my language, sorry. It's like a constant whine.
I remember, almost an years ago, I got something like that while I was building a compressor and an overdrive in a box. It was just for few days. Then it worked ok.
While, few months ago I build an Echoplex Preamp type circuit. It sounded sparkle, but nice and clean. Just I got the whine, just with the power supply, by the way, it's an old 9v Boss PSU. It works fine. I solved the problem with the Echoplex Preamp with a 1N5817 in line with the 9v.

With the Pharaoh Fuzz I got the whine with the soldered DC jack, while with another one flying connected (so, if you want, this adds messy longer wires) the whine gone away and the circuit works really good. I hope I can solve this replacing the old DC jack, just I can't explain how it worked fine just few days early.

For the Wooly Mammoth the situation seems harder, but I find a thing, actually. I had to move a pair of components, and I saw just now the 100uF filter cap in the power supply reversed. Even if I had to move those components to sovle the whine issue, so I had already it. I can't understand.
Anyway, when I reoriented it the circuit MUST work ok as early. I hope.

It's just really weird how this little accident are coincided. I still suspect there's something weird, but I hope I can solve both the situation this time.

[JackSkellington]

I worked on Wooly Mammoth where I reoriented the 100uF and I worked on Pharaoh Fuzz replacing the DC jack. Nothing, really nothing, changed!
Wooly still squeals and the Pharaoh Fuzz works just if I connect a second flying DC jack where a pair of test leads bring the ground and the 9v to this second DC jack.
It's crazy!

[JackSkellington]

I solved the whine on the Pharaoh Fuzz. I understood that the clip alligator I used in the very first test when it worked fine (I didn't solder the DC jack) probably made the difference. In the next tests the DC jack was soldered using short wires, but it squeals, and I made the circuit to work just connecting a second DC jack through the test lead.
So, a 47R in line to the 9v was ok to make the circuit works ok. Maybe a 10R was ok, I didn't try, the things was to much absurd just like that!

About the Wooly Mammoth the thing it's a bit more complex, I guess. Because the same thing, a 47R resistor in line to the 9V decreased the the volume of the whine, but it's still there, I can heard even with the volume pot of the guitar closed. Nothing change using a 1N5817 in th epalce of the 47R.
The 47uF as power filter I think doesn't work good, anymore. I tried another (on socket), and nothing changed, until after some experiment I got suddenly no whine! The new 47uF that was reversed, negative on 9v and positive on the ground. This make the circuit fine.
Maybe, the 47uF was reversed since the beginning, so I got no squeal initially. Later the cap was damaged and I got the squeal. It could be?
What does it means? I can let it like so?



Here's the schematic, but it doesn't include the power filter cap.
http://revolutiondeux.blogspot.com/2012/02/zvex-woolly-mammoth.html

[JackSkellington]

I'm sorry for the multiple posts, but I would point the attention on a particular.
Look that 1N4001 across 9v and ground. Is it bad oriented? Is notnegative side usually on the ground?

I need to know if there's something wrong with that diode, please.
Thanks!

[JackSkellington]

Probably I'll make another attempt with the Woolly Mammoth on bradboard, or make it again.
Meanwhile, I built a SHO using this layout: http://tagboardeffects.blogspot.com/2013/02/zvex-super-hard-on-compact-layout.html and guess what? It squeals with the PSU! (Of course, that it's ok with battery.)
My last four circuits had the squeal. Echoplex Preamp, but I solved with a diode in line to the 9v; the Pharaoh Fuzz, and I solved with a 47R. No way to solve the problem with the Woolly Mammoth, and now I built this SHO, and I tried to put in line to the 9v 47R, 100R, 330R! And then 1N4001, 1N4007, 1N5817 and nothing. A 100nF film across the ground, extra electrolytic caps and nothing.
What's going on?

[Willybomb]

Try sticking a buffered pedal in front of it.  If the squeal goes, put a vero buffer in the pedal before the effect.  This fixes 90% of high gain squeals.

[WormBoy]

If you get squeal with a PSU but not with a battery ... the problem is with the PSU. You might be able to fix it with filtering the power line in each circuit, but maybe you're better off with a new PSU  .

[JackSkellington]

The PSU is an old Boss, I always find it good, and I never had problem. This is really weird, because my old pedals, I tried some just today, don't have this problem.
My last two circuits I can't fix, Woolly Mammoth and SHO, have both an electrolytic cap in the power filter, and nothing I can put in line to the 9v can tame the whine.

The SHO is not high gain, it's pretty clean at medium setting, but it squeals anyway. I wanted put it in a 1590A enclosure, I'm using 9mm pots (I add the volume, too), and I can't put a buffer in front, I have not much space. As I don't want put a buffer in front of a Woolly Mammoth, because it is a fuzz.

[HamSandwich]

I hate to say it, but I'm with Worm Boy - new power supply. You might be able to fix it for your two pedals, but who knows in the future. A $20 1Spot (I guess it depends on where you live) may get you there

[alanp]

Spare PSU's are useful in any case.

Any photos?

[somnif]

Have you tested this phenomenon someplace other than your home?

I ask because I experienced something similar. Sometimes I would get horrible power supply buzz, sometimes it would be fine. I discovered my apartment has such horrible grounding that any time any of the air conditioning units in my "stack" (my room and the two above me) were running, I get power supply noise. If they're off, its fine.

Well, as fine as I ever get, there is so much EMF noise around here that I can barely use wifi 2ft from my router and my wireless headphones go buggy walking across a room....

Given that I live in Arizona, it means I prefer battery power 10.5 months of the year 

[madbean]

Have you tested this phenomenon someplace other than your home?

I ask because I experienced something similar. Sometimes I would get horrible power supply buzz, sometimes it would be fine. I discovered my apartment has such horrible grounding that any time any of the air conditioning units in my "stack" (my room and the two above me) were running, I get power supply noise. If they're off, its fine.

Well, as fine as I ever get, there is so much EMF noise around here that I can barely use wifi 2ft from my router and my wireless headphones go buggy walking across a room....

Given that I live in Arizona, it means I prefer battery power 10.5 months of the year 

This is a crucial point. Always test other outlets that are on a different breaker and different power supplies, if possible. Some mains wiring is just noisy. In my house in Austin I had one outlet that was noisy as balls and other ones that were fine. I've had one Boss PSU that turned into absolute garbage after years of use.

[JackSkellington]

Spare PSU's are useful in any case.

Any photos?

I bought maybe three years ago material to build a 9v PSU, but I never built it, I will not talk about it right now, maybe next time!

Alanp, what photos you want? My PSU or the circuit?