Hi all,
I have a few questions about this circuit. I'll ask the questions first, then describe the circuit a little.
Questions are: "What is the input impedance of this circuit, and why doesn't it sound worse."
There is no emitter resistor, and as far as know that should drastically decrease the input impedance of the circuit. I was thinking there should be about a 1k emitter resistor to maintain input impedance for a guitar. I thought I would put a 20k pot in series with 680ohms to make a drive control. As an experiment I just put the 20k pot allowing for the emitter resistance to go to zero. It seemed to work fine.
I'm guessing there's a very low input impedance, but an arbitrarily high gain 100k/0ohms and the gain is winning, but either way I'd like to sort of know what to use as the input impedance for the circuit is. I'm not even sure how to measure it because the waveform is so distorted.
This was my experiment to see how simple of a distortion circuit I could make with one 2n3904 transistor. The 100k collector resistor makes the bottom of the sine wave get clipped around .7v. The infrared led is in the feedback loop and clips the top at about .7v. Usually like in electra distortions, there is a 470k resistor, but I split this into two 220k resistors and put a .1uf capacitor to ground to increase gain (I'm actually not sure how that works but I saw it in Joe Davisson's Easy Drive Circuit and tried it as a mod. Analog Alchemy)
I think the output impedance should be about 100k so that lets me feed it into a 1meg input guitar amp.
Anyhow, for as simple as it is I don't think it sounds too bad. I ran it through a marshall type tonestack and it seemed to be acceptable to me for a simple build.
Thanks for looking and any help on figuring out the input impedance or other insights would be appreciated.
I have a few questions about this circuit. I'll ask the questions first, then describe the circuit a little.
Questions are: "What is the input impedance of this circuit, and why doesn't it sound worse."
There is no emitter resistor, and as far as know that should drastically decrease the input impedance of the circuit. I was thinking there should be about a 1k emitter resistor to maintain input impedance for a guitar. I thought I would put a 20k pot in series with 680ohms to make a drive control. As an experiment I just put the 20k pot allowing for the emitter resistance to go to zero. It seemed to work fine.
I'm guessing there's a very low input impedance, but an arbitrarily high gain 100k/0ohms and the gain is winning, but either way I'd like to sort of know what to use as the input impedance for the circuit is. I'm not even sure how to measure it because the waveform is so distorted.
This was my experiment to see how simple of a distortion circuit I could make with one 2n3904 transistor. The 100k collector resistor makes the bottom of the sine wave get clipped around .7v. The infrared led is in the feedback loop and clips the top at about .7v. Usually like in electra distortions, there is a 470k resistor, but I split this into two 220k resistors and put a .1uf capacitor to ground to increase gain (I'm actually not sure how that works but I saw it in Joe Davisson's Easy Drive Circuit and tried it as a mod. Analog Alchemy)
I think the output impedance should be about 100k so that lets me feed it into a 1meg input guitar amp.
Anyhow, for as simple as it is I don't think it sounds too bad. I ran it through a marshall type tonestack and it seemed to be acceptable to me for a simple build.
Thanks for looking and any help on figuring out the input impedance or other insights would be appreciated.