So, I'm currently breadboarding a proco rat 2, based on this schematic: http://3.bp.blogspot.com/-9PthIEWqVk0/U ... o+Rat2.gif.
I am able to get a signal through it the signal generator of my oscilloscope; which pushes out a signal of around 400mV, and I can see that when I turn the knobs on it, the signal is changed (the filter and distortion knobs visibly alter the shape of the signal, while the output knob increases/decreases the output voltage). When trying to connect the output to my amp, I am indeed getting that squarewave tone (even with a selectable amount of distortion when turning the distortion knob), but when I try my guitar, it just becomes dead silent (the guitar pushes out a signal of around 250mV when connecting the oscilloscope directly to the jack) and no signal readings come up on the oscilloscope.
Running off a lab power supply on 8.97V, and the current is limited to 0.7v.
So, any ideas of what could be causing this? Could it be some kind of impedance mismatch?
Proco rat 2, sound with signal generator, no sound with guit
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deltafred
- Opamp Operator
It could be a grounding problem.
When you use the signal generator in your scope it will share the ground with the scope so if you happened to miss off the input or output ground it would still work ok.
With your guitar you need a ground for the both input and output.
That's all I got with the info provided.
Edit - Welcome to FSB. I just noticed this is your first post.
When you use the signal generator in your scope it will share the ground with the scope so if you happened to miss off the input or output ground it would still work ok.
With your guitar you need a ground for the both input and output.
That's all I got with the info provided.
Edit - Welcome to FSB. I just noticed this is your first post.
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Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012
Thanks for the tips and the welcome!
Worth mentioning is probably that I'm using an LM741 chip rather than the LM308 (had it at home already/I'm too cheap to buy the LM308), so I removed the offset cap between 1 and 8.
After troubleshooting it further and checking for bad grounds, I couldn't find any, although I did manage to find out that the guitar signal can be traced until the input of the opamp, at output 6 (the signal output), it's just a flat signal at 1.82V; when running it with the oscilloscope signal generator as the signal input of the circuit (instead of the guitar, that is), I'm getting somewhere around 6V as the signal output of the op-amp (the output of the signal generator is around 3V; thus, my previous readings of the output of the signal generator must have been completely off).
It's almost like the op-amp has some kind of filter to not accept any signals below x.
Worth mentioning is probably that I'm using an LM741 chip rather than the LM308 (had it at home already/I'm too cheap to buy the LM308), so I removed the offset cap between 1 and 8.
After troubleshooting it further and checking for bad grounds, I couldn't find any, although I did manage to find out that the guitar signal can be traced until the input of the opamp, at output 6 (the signal output), it's just a flat signal at 1.82V; when running it with the oscilloscope signal generator as the signal input of the circuit (instead of the guitar, that is), I'm getting somewhere around 6V as the signal output of the op-amp (the output of the signal generator is around 3V; thus, my previous readings of the output of the signal generator must have been completely off).
It's almost like the op-amp has some kind of filter to not accept any signals below x.