SOLVED (vero) tc mojo mojo - op amp issue


working from this layout, which i know is unverified and has no support in the comments. built it, checked it a hundred times, i'm confident that my build is solid, but the layout might be an issue. used 5532 op amps. got no output signal. with an audio probe i was getting signal at pin 3 and then it wasn't coming out of any of the output pins. it stopped dead in it's tracks.

so i tossed in some 072's instead. passes signal, controls work. only trouble is that it's got no headroom with the gain up. sounds like it's fighting for it's life. if i understand correctly, 5532's run on a higher voltage than 072, 4558, and the like. unfortunately i do not presently have 833's or 4580's to test with, as suggested in the layout.

could my issue be power related? that the 5532's aren't getting enough power to actually turn on and pass signal? is there an obvious issue with the power section of this layout? the only difference between my build and this layout is that i used 100nf film caps instead of ceramics as pictured from pin 8 to ground on each op amp. i'd like to hope that isn't the problem, but i'm happy to be wrong.

Did some measuring. Only getting 1.5v at pin 8. Seems to be getting robbed by that 1k resistor right after the protection diode.

I found this schematic, which I’m sure isn’t quite official, but might point to the problem. Right here in that same spot there’s a resistor just labeled “1”. Not 1k, just 1. Is that supposed to be a 1ohm resistor instead? And is that even necessary? How much power would 1ohm of resistance eat up?


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IME if a resistor has nothing other then a number next to it it will mean ohms. So I think you are correct that the 1 means 1 ohm. It's not there as a dropping resistor it's to filter the voltage. It might be more common to see a 10ohm or larger.