Is it possible to invert the output of the Tube Screamer by reversing the connections to the + and - inputs on the second op-amp?
I'm building the Minimal "Son of Screamer" version. Here's a link to the schem on GEOFEX: http://www.geofex.com/Article_Folders/TStech/tsxtech6.gif
I'd like to add a phase reversal switch. I'm hoping it will be as simple and reversing the connections between pin 5 and 6 on A2.
I'm probably way off the mark. But, would it be correct to say that the second op-amp in this (http://www.geofex.com/Article_Folders/TStech/tsxtech6.gif) is biased by the first stage?
The first stage has 4.5V on the + input, which sets the idle output of the first stage to 4.5V, and this sets the bias for the second stage. Feel free to correct me if I'm way off or missed something.
bump
Soggybag is correct. Reversing connections between + and - inputs on either op-amp will cause it to be a square wave oscillator, so I don't think that's what you want to do. Probably the simplest and best solution would be to add another dual op-amp, each configured as an inverting buffer. Take the output from the first buffer as your "inverted" out, or run the output through both for "non-inverted" output... And a bonus feature, you can use both outs to have a balanced output. Think DI box.
Quote from: earthtonesaudio on June 16, 2008, 10:34:43 AM
And a bonus feature, you can use both outs to have a balanced output. Think DI box.
Wont they just cancel each other out? Or do I need to research DI?
Well I was just thinking of the typical balanced cable (XLR, TRS, or similar) which carries signal, 180 degrees inverted signal, and shield. The reason is to have them both pick up the same noise, then you cancel them out at the mixing board, so that the noise is canceled. At least I think that's the reasoning. I think the input needs to be differential in order to see the advantages, but I'm not sure. Maybe I need to look up more on DI boxes as well! :)
I guess I'm basing the assumption on how you make a HPF from a LPF - mix the untreated signal with the filtered (and inverted) signal.
Quote from: frequencycentral on June 16, 2008, 04:37:45 PM
Quote from: earthtonesaudio on June 16, 2008, 10:34:43 AM
And a bonus feature, you can use both outs to have a balanced output. Think DI box.
Wont they just cancel each other out? Or do I need to research DI?
My understanding (which may not be correct) was that DI has two outputs: inverted and non-inverted. The inverted is inverted again at the desk, and then combined with the non-inverted so that noise picked up by both on the way will be cancelled out. The wikipedia article on Balanced Audio talks about the inverted line being subtracted from the upright line at the other end- which I guess is the same as inverting and combining (addition).
EDIT: Some interesting links
http://www.mediacollege.com/audio/balanced/cable-balanced.html (http://www.mediacollege.com/audio/balanced/cable-balanced.html)
http://www.mediacollege.com/forum/showthread.php?t=4403 (http://www.mediacollege.com/forum/showthread.php?t=4403)