RAT clone gain problem

Started by pokus, September 23, 2019, 02:28:39 PM

Previous topic - Next topic

pokus

Hey there,
unfortunately I have some weird problems with one of my builds again.
It's basically the RAT schematic with some changes in the values of resistors and capacitors. A tonestack and a buffer behind it, but that's not the problem.
I get signal at the non-inverting pin of the JRC4558. Now the weird thing. On the output pin I get a signal when the pot(changed it to 250kA) is at 0 and also if I turn it up a little, then it even acts the way I want it to and increases gain. But at some point the tone cuts off and keeps that way no matter if I turn it to 10 or else. It doesn't really cut off, but it can only be heard if I heavily increase the input volume. It seems like there is a zener somewhere, cuts the signal when it reaches a certain point. There is one between +9V and GND, but that really can't be the reason. The diodes (used red LEDs) light up when the pot is somewhere in between 0 and until the point tone cuts off. Also realized tone at inverting input becomes very bassy when it hits that point. Measured the pot, it seems ok. Also the voltage measurements are the way I expected them to. The tonestack is doing his job and I already changed the opamp.
What could it be? Very appreciate any kinds of suggestions.




PS: There is a very very small range between maxed tone and no tone where it gets kind a distorted, like it's dying there. Don't know if that helps. :D


thetragichero

could it be something dumb like electro cap orientation/bad electro caps?
do you have a schematic drawn out of what  YOU'VE built? sometimes I've found for myself if i don't draw out what i want to build and go from the stock schematic something gets lost in translation (things such as pinouts using a dual op amp instead of a single with compensation cap could certainly trip me up)

GGBB

Quote from: pokus on September 23, 2019, 02:28:39 PM
Hey there,

It's basically the RAT schematic with some changes in the values of resistors and capacitors. A tonestack and a buffer behind it, but that's not the problem.


What specifically are those changes? The gain in a RAT is crazy high and changes to filtering can send the opamp into fits.
  • SUPPORTER