Ridiculously loud output volume with Roboto


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I just completed the Roboto. It kind of works, I'm getting lots of crazy sounds, reminiscent of a ring modulator more than anything, but the output volume is absurdly high and it doesn't sound much like the demo videos. I can only the volume up a hair past 0 before it gets unbearably loud. I turned the gain trimpot all the way down with little effect. I also double checked that I have the correct pots and resistors R8 - R11 along the output path. I even replaced the TL072. No dice.

I'm an experienced builder, and this is a relatively simple build, so I'm kind of surprised there's an issue. My first thought is that I got a bad HT8950, but it looks to be in good condition and I'm still getting a signal coming through.

Has anyone else experienced this? Or know of a reputable source for an HT8950?

Thank you


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IMG_20220325_131003505.jpg IMG_20220325_130931066.jpg


Just checked the voltages on the regulator... outputting 3.28V, so we're good there. Confirmed that's what's feeding the TL072 non-inverting inputs. Even if a cap value is off, idk how that would so greatly affect the output volume. I also measured the volume pot before installing, so I don't think it's that. Seems like it's gotta be the HT8950 chip.

Edit: It's in a box with 2 other pedals, that's why the jacks aren't grounded to the board, they're grounded to the sister pedals.
Last edited:

Dan M

Well-known member
I would color code check all of the resistors. Maybe you installed a 47R instead of a 47k, etc. I’ve done that before.

I’ve never found a bad component. I’m sure it can happen, but in my case it’s always been bad soldering or incorrect component install.


New member
Hey everyone, thanks so much for the replies. I will investigate further as soon as I get a chance, since it's such a simple circuit I will end up reviewing every component individually. I also agree that I could probably use a bit less solder and may as well clean the board to see if I made any errors.

I already tried swapping out the TL072 any it didn't change anything.

I did check the voltages on the regulator and ICs and they were correct, but I agree I will probably need the probe to identify where the boost actually occurs.