UPROAR

[edlofau]

Hi,
I have problems with C5 (100nF) in UPROAR model. It seems to be cutting the signal little by little until nothing pass to next stage (IC1B). If I shortcut it, the signal doesn´t dissapear but i got lot of noise. I am using an MKT standard, not a Panasonic ECQ, could it be the root of the problem? How critic is the type of capacitor in the design?
Thanks friends!

[madbean]

Have you tried using a different cap there? Using an MKT or any other type should not be the source of the problem, unless the cap itself is bad. While it is not totally necessary to use a cap to decouple between between the two stages of the op-amp, there is a little more going on there due to the nature of how the gain control is set up (very similar to a  BluesBreaker). Without it, the noise source might be caused by the impedance feeding into ICB...although I'm honestly not totally sure.

Perhaps socketing C5 and trying some other values will cure the problem. Try values near 100n.

[edlofau]

Thanks brian,
I tried with different caps 100, 200, 36n.... with negative results, I use JRC4558 intead 4580 opamp, i don´t know wether a diference in impedance input or something, could be the problem, I guess not. Ive noticed gain POT doesn´t make a considerable effect...

[jkokura]

It sounds to me like you have larger issues than just that going on. Perhaps a picture of the board and the solder side would help us out?

Jacob