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PostPosted: Sat May 02, 2020 6:28 pm 
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So this was originally going to be a post about modifying a Yellow OD for more output volume. Here's the text I was originally going to post:

"Hello, I recently purchased a BYOC Yellow OD (the last one I think, because it's out of stock now and there's a disclaimer that there likely won't be any more because of the scarcity of the op amp chip). Anyway I really like it, a lot more than my Ibanez TS Mini. I love the EQ curve of it. I've noticed two things though;

1. I'm noticing the volume seems to randomly come up and down a little bit when the pedal is engaged. It's only really noticeable on a clean channel, and I mostly use it as a boost for a dirty channel, which I think it could probably be solved by re-flowing all the solder joints. No big deal, I've done that with every pedal I've built. But I'd be open to any suggestions as to what it might be specifically.

2. I'd like to modify it for a little more output volume. There's an audible drop in volume when I use it on a clean channel, I think it's sort of dealt with by the compression of the heavily overdriven channel on my amp. Like I said, I don't use it with a clean sound a whole lot, but I'd prefer it be at unity gain if not higher output. So based on my limited knowledge of electrical engineering, I think that means swapping out resistor 12 or 13, but I'm not sure if that should be for a higher or lower value, and how much higher or lower."

So before I posted that, I plugged it in and tried it out just to make sure I was describing my issues correctly. The gain knob gets stiffer when you turn it past about 11 o'clock, which I had noticed the whole time but didn't really think much of it. I mostly use it as a metal boost type thing with the volume all the way up and the gain knob at about 8 o'clock. Anyway up until turning it past that 11 o'clock position, it basically sounds fine, but after that it basically turns into a gated fuzz. Which is cool but not what I'm after. What's more, I just listened to a demo of an actual Boss OD-1 (what this pedal is a clone of) and noticed that it's a very clean pedal with the gain turned all the way down. When I have the gain all the way down on my Yellow OD, it's already pretty distorted. I've heard of things like that happening with fuzz pedals that use germanium clipping diodes, but the diodes in this pedal are silicon and I'm pretty sure they're not used for clipping in the circuit. But I could be wrong about that.

So I guess I'm asking,
1. I'm sure at least one of those issues is related to the pot. As per the schematic/parts list it's an "A1M Audio Drive pot," Would getting a new one solve the output volume issue as well?
2. Which component should I change for more output volume and to what value?

I'm 99% sure I haven't accidentally put the potentiometers in the wrong sockets, but I'll definitely check that when I get around to cracking it open.
Whenever I have this all sorted out, and when the coronavirus quarantine ends, I'll finally paint it and whatnot. The anime nerds among you will like the color scheme I have planned for it. I think it's the last Yellow OD from BYOC because it was displayed as out of stock shortly after I got it and there's a notice that there likely won't be any more due to the scarcity of the op amp chip. So I want to make you all proud with it.

Below is a picture of the schematic for reference.

Thanks in advance.


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PostPosted: Sun May 03, 2020 11:41 am 
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There's a LOT of ground to cover from the points you've raised. I'll try to address several of them:

  • Volume fluctuations are usually (but not always) due to a wonky connection somewhere. The first thing we always suggest when this behavior is present is to do a full reflow of the pedal's solder joints. It is amazingly effective in curing such issues and takes a lot less time than trying to chase down the specific joint(s) causing the problem.
  • A lack of volume is NOT something I would associate with this circuit. Into a clean amp (an Allen Sweet Spot, basically a modernized blackface Princeton Reverb circuit; they don't come much cleaner), with the Drive set at midpoint, my Yellow OD hits unity gain with the Level knob at right about 9 o'clock. With the Level dimed, it is VERY LOUD. At no drive setting does mine ever become a gated fuzz, and it is indeed quite clean with the drive down all the way. Taken together, your observations indicate something wrong in the build; might be a connection problem but could also indicate a misplaced component(s). A set of photos would be helpful. They need to be LARGE, well-lit, well-focused shots of BOTH sides of the PCB and all of the switch and jack wiring.
  • The pot starting to feel stiff at some point in its travel is most often due to the knob being too far down on the shaft and binding against the top of the pot as it turns. Try loosening the set screw and pulling up very slightly on the knob, then re-tightening. If that doesn't cure the stiffness, then replacing the pot is probably in order.

We can tackle the "more volume" question, if necessary, after addressing the above points.

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PostPosted: Sun May 03, 2020 7:10 pm 
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Alright so the good news is that the knob is fine. There's nothing wrong with the pot, it's just that the knob was too low on it.

The bad news is that after resflowing all the solder points, it's still basically not working. I guess the one improvement is that it will work fine for a little bit (proper output volume, overdrive not fuzz) and then randomly go back to how it was before where the output drops and it's too distorted and becomes a very nasally gated fuzz when the drive knob gets turned up. But this time when it goes past about 2 o'clock instead of 11. So hurray for progress?

There's pictures below. I will mention I reflowed all the solder joints once, it seemed to be working. Then I noticed I hadn't tightened the nuts on the I/O jacks all the way, so I tightened them by hand without holding them still on the inside (rookie mistake I know). Then it was in its "malfunctioning" state we'll call it. I figured I had pulled some of the wires by turning the jacks around and I focused on reflowing those solder joints which are accessible without removing the PCB from the housing. And ultimately redoing the power jack wiring entirely. And that basically brings us to where we are now: working fine for a little bit, then going to malfunctioning. I also think I stripped some of the PCB plastic between the joints on two diodes, which you might be able to see in the picture. That's the metal in the PCB itself and those components are supposed to connect there anyway. Also the performance has overall 'improved' since I did that so I'm not worried about it.

Should I try to reflow every solder joint again?


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PostPosted: Tue Sep 15, 2020 9:36 pm 
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Start with the solder pads that are sort of flat looking. I'm looking at the jack connections in particular. You want little Hershey Kisses of solder on all your solder joints.
When I have issues, I'll go back and touch the joints, but I don't add solder. It helps rule out cold solder joints and also helps find ones that might need more solder too or a busted lead.


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PostPosted: Wed Sep 16, 2020 11:26 am 
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Increasing the value or the R9/10k resistor will increase the output. However, I really wouldn't worry about that. You've clearly got something wrong going on, so I'd fix that first, and then see if you want to modify it.

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