Kingslayer 2 gain control issue?

[zilla]

All,

Just finished building my first kingslayer 2

The pcb mount dual gang is great, same with the simplified stomp switch wiring.

But

I ran into an issue:  when I roll the gain down to 0, there is suddenly a very large amount of rfi noise. Doesn't matter what the other controls or switches are set to. And it's there until the gain knob is rotated about 10-15 degrees and then abruptly stops.

Does this sound like a bad pot, or is there something else afoot?

[the3secondrule]

I've discovered my sunking2 build has the same issue. With the gain pot all the way down, there's a heap of squealing and oscillation. It can be heard in bypass as well.

Not sure if this is related, but with the gain all the way down, there's also a pretty big pop when switching between bypass and effect, and vice versa...

[madbean]

Hmm, I don't have a straight answer for that.

Did you guys both build it TB or Buffered?

[zilla]

i made mine buffered (no pull down resistor, and no buffer bypass)

[madbean]

I don't follow. You said it's the buffered version but it is not buffered bypass? What does this mean, exactly?

[zilla]

your KTR mod that allows you to switch between true bypass and buffered.

This build is straight up buffered.

[madbean]

Okay, thanks. I'll look into my build to see if I can replicate the noise somehow. I'll report back.

[the3secondrule]

Just on a bit of a hunch, I replaced my opamps (I had used TLC2262's), with a couple of 4558s. Bingo, noise gone.

Zilla, what chips did you use?

[madbean]

Yeah, the 2262's are rail to rail and are rated +/- 8v, where the Sunking is +18/-9v. 4558 may not be the best choice either if you want the true "Klon" sound since they a BJT input rather than FET like the TL072.

[zilla]

i used one of these charge pumps (can't remember which)
ICL7660SCPAZ
or
TC1044SCPA

and one of these TI chips. can't remember which:
TL074BCNE4
or
TLC274BCNE4

i think it was the 274, but i'm not 100% sure.

[the3secondrule]

Yeah, the 2262's are rail to rail and are rated +/- 8v, where the Sunking is +18/-9v. 4558 may not be the best choice either if you want the true "Klon" sound since they a BJT input rather than FET like the TL072.

Makes sense. I was sure I'd read the 2622's could be used, but of course I can't remember where now...
I've got some 072's I can throw in but it sounds pretty good right now

[zilla]

I'll try swapping out the IC tonight and see if that makes a difference.

[the3secondrule]

Just had a look at the data sheet for the 274, looks like it's rated for 16v.
So if you used a 274, swapping it out for the 074 should fix it...

[zilla]

confirmed that it does have a 274 in it now. Will try the 074 tonight.

I don't recall ever having this issue with the original kingslayer and a 274 chip. strange.. maybe it's a bad chip?

[madbean]

The KS pushes the 274 a bit beyond its limits, but I have not had a failure yet. It seemed reasonable enough to put that in the BOM considering the 274 sounds really good in this circuit. Once you account for voltage drops across the power supply and out of the charge pump, it ends up about 1v or so over spec. But, if there does turn out to be an intermittent issue with noise and the 274 then I might need to address that in the build docs.