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?
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...
Hmm, I don't have a straight answer for that.
Did you guys both build it TB or Buffered?
i made mine buffered (no pull down resistor, and no buffer bypass)
I don't follow. You said it's the buffered version but it is not buffered bypass? What does this mean, exactly?
your KTR mod that allows you to switch between true bypass and buffered.
This build is straight up buffered.
Okay, thanks. I'll look into my build to see if I can replicate the noise somehow. I'll report back.
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?
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.
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.
Quote from: madbean on May 27, 2014, 07:50:33 PM
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
I'll try swapping out the IC tonight and see if that makes a difference.
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...
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?
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.
Damnit. I went to pull the 274 out of the socket and it was being difficult and I had to apply some brute force to get it out and I think I broke something because the circuit passes no sound now.
Going to have to troubleshoot tomorrow night.
Can someone post the voltages on their quad for reference?
I assume this is the proper pinout?
(http://circuits.datasheetdir.com/37/UTC-TL074-pinout.jpg)
Well, the KS is a split rail design so the bias voltage is actually 0vDC. This means you should have +9 on pin4, -9 on pin11 and 0v on the other pins. There isn't much to break on an IC other than the solder pins.
I'm just starting to build a Sunking II and a Kingslayer into dual pedals with optical comps. Before I get going is there an answer here regarding this issue? Which opamps should I get, use order etc.
Thanks!
what i thought was me breaking the pedal was an embarrassing mistake that we shall never speak of again ;)
anyway, swapped out the 274 with the 074 and the weird RFI noise disappeared.
I might have had a bad 274, but i don't have any other 274 chips kicking around to verify. I tried a few 074 chips and the noise didn't come back.
Maybe the 274 isn't suitable for this circuit anymore?
has anyone been able to confirm this?
Is there a sound improvement using the 274 over the 074? May be a dumb question but I was about to order some 074s and since I read this thread about noise issues, I will stick with the 074s lol
I made an original kingslayer with the 074 and I love that pedal! 8)
I am having this same issue.
I used - TLC274CN From Mouser
And - TC1044SCPA Mouser
I think the pedal sound F*cking Fantastic!! Other than most people use it as a clean boost and run the gain all the way off. This could make a person feel there is something wrong with the pedal if they encounter this.
I would like to try other options to get rid of the unwanted noise, but I dont want to sacrifice the awesome sound.
Any suggestions?
-Shane
Okay, I'll check into this further tomorrow, for sure.
Quote from: sdlogan9 on June 24, 2014, 01:37:14 AM
I am having this same issue.
I used - TLC274CN From Mouser
And - TC1044SCPA Mouser
I think the pedal sound F*cking Fantastic!! Other than most people use it as a clean boost and run the gain all the way off. This could make a person feel there is something wrong with the pedal if they encounter this.
I would like to try other options to get rid of the unwanted noise, but I dont want to sacrifice the awesome sound.
Any suggestions?
-Shane
I guess the only thing is to add a resistor in parallel with the gain pot to keep a minimum value when the pot us set to zero?
Quote from: zilla on June 24, 2014, 03:57:11 AM
I guess the only thing is to add a resistor in parallel with the gain pot to keep a minimum value when the pot us set to zero?
It has a minimum value. That's what the little resistor hanging off the wiper is for in the first Kingslayer.
A resistor across the pot will just shrink the pot's value, it won't do what you're looking to do.
Quote from: madbean on June 24, 2014, 02:34:10 AM
Okay, I'll check into this further tomorrow, for sure.
Any up dates should I order a 072 or should I assume my 274 is messed up?
-Shane
I got the same thing at the clean end of the gain knob—only affects the first 5% or so of the control, then the whine stops.
True bypass btw.
I am pretty sure I know what's causing the problem. I'll check in here in a couple of hours with more info.
I was wrong on what I thought the cause was. In fact, my prototype had no noise problem with the gain pot as described. After looking a bit further, I found the culprit: I did not test a TLC274 in this build but a TL074. With the TLC274-same result as you guys. So, I can confirm that I am an idiot.
Sorry guys, I should have figured this out sooner. Use a TL074 for now. I'm going to do some part swapping and see if I can get the noise to go away. Somehow, grounding the input of the gain stage is causing the IC to go into oscillation. Previously, I had a 2k stopper resistor between the wiper and ground (on KSv1), but I switched it to be more like the Klon way which is to put it between the outside lug and the wiper. I don't remember if I did it this way because I found the same problem back when I worked out KS1, or not.
The good news is it still sounds great with the TL074. I just thought the TLC274 sounded a little bit better on KS1. I'll see what solution I come up with to make it work again.
Aha! Easy solution has been found: increase R28 to 120R or 150R. This drops the supply voltage down a bit, just enough so that it does not cause the noise problem.
At 120R, I measured right around +/-8v on the TLC274. With 150R, it was about +/-7.8v under load. So, either should be fine. You can still use the TLC274 and no noise when the gain is all the way down. I'm putting 150R in the updated doc just to be on the safe side.
-- If anyone needs the resistor, let me know and I will mail you one. I have carbon film.
So I tried this and put the 150R 1/4 watt in place of R28 and still have the same noise!! :(
Any ideas?
-Shane
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Ok so I robbed a 072 out of a Kingslayer I that I happened to have... Don't know why I didn't think of this earlier :) !!!
And
Voila it works like a charm!!! No more noise problems!!
My recommendation would be to just use the 074's to avoid any possible problems.
-Shane
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Shane, you mean a TL074 right? Not a TL072?
I will check into this some more today. I have a few other TLC274 chips on hand. I'll see if I can break it again. At least I'm glad you were able to get it working correctly.
Ya I meant a TL074CN...
I robbed it out of a " Kingslayer I " - build I had.
Peace
Shane
Quote from: madbean on June 27, 2014, 02:34:13 PM
Shane, you mean a TL074 right? Not a TL072?
I will check into this some more today. I have a few other TLC274 chips on hand. I'll see if I can break it again. At least I'm glad you were able to get it working correctly.
Brian did you get this to break again,?
I really want to build this lovely beast soon..
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