Ridiculously loud output volume with Roboto

jpier2012

New member
Hello!

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
 

jpier2012

New member
IMG_20220325_131003505.jpg IMG_20220325_130931066.jpg

Woops

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.
 

jpier2012

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.
 
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