Hey all,
Just got interested in pedal building and have done a lot of research on the topic. Before building my first pedal (GGG's ITS8), rewiring an electric guitar was as far as I've ever gone in the electronics field. So this has been a very enlightening and exciting project.
I am getting a lot of excess noise out of this thing when it is plugged in. I performed the "Very Expensive Boutique" mod on it. I have tried resoldering a lot of joints on the PCB (the ones that looked the worst to me), and I'm not sure what else to try. I know that I have everything in the right place, because it works very well and sounds very nice, but when I'm not playing anything there is just an awful background noise.
I think that most of you will say the soldering job isn't quite up to par, and honestly, I hope that's what the problem is. This was my first project and my first time ever soldering components to a PCB. I'm including a picture of the back of the PCB so you can see what you think about the soldering job.
Your solder joints look fine. I would take a pair of nippers and trim off the excess wire and lead length just for neatness' sake. I doubt that has anything to do with the noise though. Sorry, no help I guess.
Yeah, I'm with Scott, your solder joints don't look bad, I would clip off the tips as well.
I think a little more definition on "Excess Noise" is probably in order. I take if from your post it's adding a white noise to your amp when you're not playing.
Is it buzzing like a bad ground?
Are you using a wall wart or batteries (bad/dirty power supplies through overdrives can sometimes equal noise)?
Are you playing through it with single coils? 60 cycle hum run through an overdrive only gets less pleasant.
Does the noise change when you mute the strings or touch the bridge? This might indicate a bit of a grounding issue with your guitar that's being amplified by the pedal.
Quote from: GermanCdn on June 23, 2014, 10:09:11 PM
Yeah, I'm with Scott, your solder joints don't look bad, I would clip off the tips as well.
I think a little more definition on "Excess Noise" is probably in order. I take if from your post it's adding a white noise to your amp when you're not playing.
Is it buzzing like a bad ground?
Are you using a wall wart or batteries (bad/dirty power supplies through overdrives can sometimes equal noise)?
Are you playing through it with single coils? 60 cycle hum run through an overdrive only gets less pleasant.
Does the noise change when you mute the strings or touch the bridge? This might indicate a bit of a grounding issue with your guitar that's being amplified by the pedal.
Right. It sounds like white noise. Doesn't seem like a bad ground kind of sound. Playing through a guitar equipped with hum buckers and I know it's grounded well. It does not go away when I touch the bridge etc. I have tried it both with a battery and through the DC jack. The same result both ways. I'll clip the tips of the wires off and see if it helps.
Yeah didn't seem to help any...
Make sure it isn't too close to your computer and turn off your soldering iron. Those can both cause some nasty noise. What kind of noise do you get? A lot of hum is eliminated when you box it up.
Ive got it in the box now. Just don't have everything screwed in all the way. I figured that was the best way to test it out without having to worry about the hum before I build the debugging unit.
It's like GermanCdn said. It sounds like white noise. And I don't hear it when the pedal is not engaged. It gets louder when I turn the Drive knob up, you can definitely hear the tone knob changing the frequency of the noise too. And it becomes quitter when I turn the Volume knob down.
Did you socket the opamp? If so, it might be worth swapping it out to rule that out. Maybe an over cooked transistor leg?
That was also my first build. I've done a few of them and never had noise.
Hmm. I did have some trouble getting the socket in the first time (originally put it in backwards lol), and it took me a long time to take it out. I was worried I might have ruined it. Now that you mention this, it reminded me! I'll run out to RadioShack tomorrow to get a new one and try it out. I'll post back here afterwards. Thanks for reminding me about that Leevibe!
It really wouldn't matter if the socket was in upside down as long as you had the chip in the right way. Did you power it up with the chip in backward or did you flip the socket around before you loaded the chip in? Or did you just solder the chip straight to the board?
If you soldered the chip straight to the board upside down and then desoldered it and flipped it the right way, I'd say there's a good chance that's where the problem is. Lots of opportunity for heat, static, or mechanical damage.
I guess that makes sense now. I had soldered in the socket right after I did the resistors and realized it was backwards compared to the picture on GGGs website. And while I was trying to take it out I thought I might have ruined it. But I flipped it around and soldered it back in. When I put in the IC, it seemed like it was a little tilted lopsided. Would it be worth it to go get a new socket? Or do you think I should just solder the IC directly into the PCB?
If the socket is a little crooked, that's no big deal as long as the solder joints are good and there are no solder bridges between the pads. You don't want to desolder it again unless you absolutely have to because you could lift a pad or a trace. If you have another opamp to pop in, that would be a cheap easy thing to try.
Ok I tried a different IC and I actually didn't even get a signal. So I put the JRC4558D back in and I had a signal again. There was still white noise, but for whatever reason, the other IC didn't give me a signal. It did however give me some noise as well.
Here are a couple of other things to look for / what i would check.
-Make sure the in and out jacks are touching the bare metal of the enclosure.
-Double check the resistor and capacitor values in the BOM.
-take the LED out. Might have a bad ground or be causing some interference.
-Make sure all grounds from the jacks and switch are good.
Do you have an audioprobe? It'd be interesting to probe the circuit and see where exactly the noise gets introduced to the signal.
Quote from: muddyfox on June 24, 2014, 09:58:41 PM
Do you have an audioprobe? It'd be interesting to probe the circuit and see where exactly the noise gets introduced to the signal.
This is a good point! If you don't have an audio probe, it's a good next project and it will save you a ton of stabbing in the dark.
Alright. Well I guess I'll put this on the side till I get the audio probe finished. Thanks for all the help. I'll post here again once I finish it and try to track the problem.
Also, different opamps have different pinouts, so make sure to look up the pinout for the particular opamp you trying. For that circuit you need a TL072 compatible chip, which the JRC4558D is. If you tried another chip and it didn't work, it may be that it's got a different pinout.
The kit I ordered included a couple other op-amps for me to try, so I used one of those.