LPB-1 into OD = much noise

[jessenator]

So I've been working on integrating a boost circuit into other effects with some mixed results.

My most frustrating application is trying to add it to a Soul Food-like circuit. When it's out of the enclosure—in its own printed deal—it works just fine and I like the overall effect of boosting a boost/OD quite a bit    INSIDE the same enclosure is another story...

When it's sharing enclosure space I get a squeal which ranges from mild to deafening (that isn't feedback). Even when it's out of the audio loop (but still powered inside the box), I get the same noise. I don't know if that's the charge pump picking up and exacerbating the noise into the signal path; i.e. proximity, or if it's something else I'm unaware of.

My LPB-1 is a strip/vero/tag board layout from TagboardEffects. The kloverdrive circuit it set up like normal with an 7660H charge pump (to avoid the noise problem found in lower-frequency-switching varietals). I have the +9V supply into the boost board coming right off of pin 8 of the 7660 (I also tried it right off of the +V line before and after the power filtering with the same result).

I've had this board (which is a lightly-modified CodaEffects design) for a bit, but didn't want to ship it off to JLCPCB if this is just the Nature of the Beast™/Cost of DoingBusiness©

Also, if this is improper, I'll remove it. I didn't see it in their store, so I figured I'd make them vs strip boarding it every time.

Again, I'm not sure what's causing the issue, if it needs to be isolated or if I'm just being NoviceMan again.


The strip board is wrapped in masking tape, but this is it hooked up to my nolK board. Don't judge too hard, I had wired, re-wired, and re-wired this many times, and at the point I took the pic I just wanted some connection to see if I was going mad.


Some exposition here:

So I was going to save this for a user project, but, and I know it would be hard to believe, I didn't consciously connect two of Brian's other projects (or even look deeply at any of them beyond the original Sunking), so my "originality" that I pompously thought I had, wasn't original at all. I'm sorry, Brian, seriously. This is actually the second iteration of the board (the first one being interestingly shaped, but many signal problems). So this is going to appear quasi-plagiaristic in the name dept—I swear it was subconscious at most; I was just hooked on Sunking, kill the king, blah blah excuses, I'm sorry, this wasn't intentional—Basically I wanted to just switch from the different clipping diode pairs I had from the original Sunking documentation (1n34a, 1n270, 1n60, BAT41). I found an affordable 4PDT slide (a 5PDT wasn't affordable or in stock when I looked).

The whole enterprise was to be a sort of middle finger to the K-purist mentality, and just pick a sound you like and play... "No gods. No kings. Only tones." so to speak. Anyway... I had it all planned out, even commissioning an illustrator friend of mine to do some custom art for it, and again, I got in way too deep and rushed it all, like I usually do with projects.

I still didn't give up... I actually made another board design which integrated the LPB-1 circuitry and skipped the two-board design. It was a complete disaster. The squeal is a CONSTANT. Anyway, here's the mushroom of death:

After I sulked for a bit, I decided I still didn't want to give up...


TL;DR I'm back to the split-board design and would appreciate any insights on the noise I'm getting.

I'm planning on trying a couple of other OD circuits, just to see, but am still waiting on parts.

[jimilee]

You've encountered heterodyning. How to fix it? You can search the forums, there have been lots of examples hashed out here.


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[mauman]

Unfortunately, the LPB-1 is VERY sensitive to noise on the +9V supply.  As in, best to use a 9V battery rather than a power supply.  And it sounds like the charge pump is putting out noise on the +9V bus to the LPB. If so, you can add a filter on the +9V supply just before the LPB, something like the sketch below will cut 10 kHz and above by more than 60 dB.   If that doesn't help, let us know, another possibility is that there's radiation from the cap that's between charge pump pins 2 & 4.  Those can send out a fierce square wave in the audio band that will be picked up by nearby jacks and wiring, although your LPB is a good distance away.   But if so, that can be mitigated by shielding the cap.

[jessenator]

Unfortunately, the LPB-1 is VERY sensitive to noise on the +9V supply.  As in, best to use a 9V battery rather than a power supply.  And it sounds like the charge pump is putting out noise on the +9V bus to the LPB. If so, you can add a filter on the +9V supply just before the LPB, something like the sketch below will cut 10 kHz and above by more than 60 dB

I'll give that a go! Thanks, Mike.

[jessenator]

add a filter on the +9V supply just before the LPB, something like the sketch below will cut 10 kHz and above by more than 60 dB.

That did the trick! we're noise-free on the boost side! Thanks again, Mike.

I'm going to try this mod on the combined board (as well as the standalone board) and see if I can't get the same results. Knowing me, I jacked up something else on it somewhere along the line, too so