Kingslayer crazy Squeal

[toddvirgil]

Ok, So I just put together another Kingslayer -- and I'm getting a crazy squeal when I max out the gain settings (i.e. OD clipping on, turn up the gain and the tone or the volume) and I get a high-pitched squeal over the top of everything. other than that it works as expected.

I realized that accidentally used a 7660SCPA instead of a 1044, so I swapped it out, but no change. Is it possible that the 7660 damaged something? Should I replace the TL274 and the zener diode?

Thanks in advance fo rthe help.

[ggarms]

I built the sunking and have had the same issue. I used the 1044 scpa chip, but whenever i put gain past 9 or so oclock I'm getting the squeal. That one's in the pile until I have more time to debug. Good luck though, you'll find this is a really common issue by searching around the forum. A lot say it's solved by changing to the 1044SCPA designation.

[wgc]

Also, check the Zener

[toddvirgil]

Ok, so I've built 4 now all with the same issue (after having built many before with no squeal!). If I turn down the tone to 3 o'clock (about 75%) it cuts out. Same if I pull the 5n6 from the tone stack. W

1. the squeal is kind of a high-pitched whistle that stays at a constant frequency.
2. Pulling and replacing the zener had no effect on the squeal.
3. Tested both ICs in a known working box, and they are fine.
4. With an audio probe, I get squeal on all of the opamp outputs.
5. I don't get any squeal on pins 1 and 2 of the tone control, but I do on pin 3.
5. The squeal only happens with my telecaster, but not with my gretsch (with tvjones pickups).

It seems the only way to get rid of the squeal is to pull out the frequencies, but I'd rather not do that

What should I check next?

[madbean]

If you are running high gain, tone, and volume settings all at the same time this can happen. I've checked this against the Sunking/Klon and it's the same thing on my builds so it is not an issue specific to the Kingslayer. With a Tele, you really should not need to set the tone knob so high...it's going to be exceedingly bright that way (painfully so on mine).

One change I am making for the forthcoming Kingslayer/Sunking II PCBs is suggesting a 6k8 (or even 10k) in place of the 1k8 resistor in the tone section. This shifts the frequency range of the tone control down so you get a bit more cut on the low side and not so much treble boost on the high side. This also has the benefit of reducing or eliminating a lot of that squeal when you start pushing all the knobs up. It does not eliminate it completely, but at the same time, the Klon is not really an effect where you dime all the knobs anyway.

One thing I have not tested is the behavior against different charge pumps. I do remember that during the Kingslayer development I used the TC1044SCPA consistently and did not have a problem with any squealing.

[toddvirgil]

Thanks Brian,

6k8 still got me the squeal but the 10k did the trick. I was feeling like maybe it was an issue with one of my components, because previous versions I've built with the exact same components didn't have this problem, or maybe I just didn't notice it .

Thanks!

[jtaormina]

Has anyone come back to this topic? I just built a Kingslayer II with the 274 and i get crazy a squeal after it sits for a little while. Also when i disconnect power it also sputters while the pwr supply cap discharges. Strangely if i play through it for about 5 mins i get a motor boating type sound. The build doc states any quad op amp, I've tried a lm339, (no sound at all) lm324 (sound but is super noisy) and the 274 it calls, i don't have a 074 yet, i need to order it still.  I was thinking that i could increase the dropping resistor a little above the 150R (R28 i think it is) that it was changed too to lower the operating range a tiny bit. Anyone else have this problem still?  It really does sound cool until it starts acting up.  I bought some Chinese greenies from ebay, i hope one of those isn't bad...

[jtaormina]

no one else still is having this problem still? Maybe i have something really botched...i finally bumped the R28 value up a little and still has a squeal. It actually gets really muddy after a minute of playing with gain all the way up or a amplified squeal with gain all the way down. I hope that new IC does the trick...

[Terrapin]

I just built this, and I get the squeal and sometimes the motorboating. It's still attached to the breadboard, and one thing I noticed is that when it squeals and I touch the tonepot (which has no knob on it), the squeal is slightly but noticeably reduced. Maybe there's a grounding aspect to the squeal?

I used an ICL7660S and TL072's.

[dbp512]

I just build an OCD drive that does the same thing with the gain and tone cranked up. When I connect the brightness toggle it gets significantly louder and higher pitched. I tried looking for something causing it, but I wasn't.

[riffermadness]

I also am having this issue. I tried both chips with the 9.1(1044 and the 7660) because I have had an issue with chips on other neg volt pedals previously. I'm worried that the tone resistor wont fix my issue because this squeal is constant, no matter what position the knobs are in, whenever I hit a note you can hear it on top. And its really high pitched, like 15khz or something.  Its not extremely loud but its constant and in the background only when the pedal is on. If I turn up all the knobs I get an incredibly nasty feedback loop thats about 3khz. I wouldnt use the pedal like that, just seeing if it may help solve the issue. Have any of you guys been able to fix this issue? Or where should I start to troubleshoot it???  Thanks for any help in advance.

[m-Kresol]

please check and post your voltages and pictures of your build.

Do you have any other pedals in line with the kingslayer? I had an issue once with heterodyning, when I had two pedals with charge pumps on my board. They did not like each other!

[riffermadness]

IC1: 6.5mv, 6.5mv, -0.1mv, -8.25v, 1.7mv, 3.1mv, 22.6mv, 8.80v

IC2: 31mv, 2.7mv, 0, -8.25V, 0, -3.7mv, -38.3mv, 8.80V

IC3: 8.80V, 4.43V, 0, -4.1V, -8.25V, 5.97V, 5.79V, 8.80V

I'm still new to building pedals so go easy on me. I've only built about 5 so far. No other pedals in line. Pedal by itself, and squeal stops when pedal is off. So its def something happening in circuit. Thanks for any tips/help!

[riffermadness]

that IC3 pin 4 is reading -4.1 volts, could this be the issue?

[m-Kresol]

hmm. voltages do look ok to me. The charge pump (IC3) is a bit off, but the important part is that -8.3V come of pin 5.

I would start by going over both sides of the pcb with a magnifying glas to look for shorts (I can't see any, but always good to make sure). Also double check all part values and orientation. Reflowing the solder joints can help too, if there is a cold solder joint.

Other than that, I would suggest audioprobing the circuit to see, where the noise is introduced.