It has been a while since I have learned about impedance so I was wondering if somebody could tell me what the output impedance of this guitar effect circuit would be.

http://topopiccione.atspace.com/pjimages/HarmonicPercolator.sch.png

Thanks,

Ryan

 

The answer is kind of complex. The output pot can make the impedance = zero at one end. At the other end, the impedance of the transistor stack is about 63K but that is modified by C6 which is 16K at 100 Hz, 1.6K at 1000 Hz etc and that is modified by being in parallel with the output pot. I guess it is sufficient to say that the next stage should be a few hundred K input impedance.

Not a very good answer but my brain would have to stretch to write the equation and most amateurs would just call the equation gobeldegook useless...so I did an estimate of the bottom line, which is useful.

 

The answer is kind of complex. The output pot can make the impedance = zero at one end. At the other end, the impedance of the transistor stack is about 63K but that is modified by C6 which is 16K at 100 Hz, 1.6K at 1000 Hz etc and that is modified by being in parallel with the output pot. I guess it is sufficient to say that the next stage should be a few hundred K input impedance.

Not a very good answer but my brain would have to stretch to write the equation and most amateurs would just call the equation gobeldegook useless...so I did an estimate of the bottom line, which is useful.

The volume pot in a guitar is usually somewhere around 50k, so the PA won't notice much difference.

There are various buffer/impedance converter boxes that present over 1M to the guitar, the volume pot is still in there - so most of the effect is less loading on the length of the coily cable.

They rarely bother to bring the output impedance much lower than about 22k.

 

It has been a while since I have learned about impedance so I was wondering if somebody could tell me what the output impedance of this guitar effect circuit would be.

http://topopiccione.atspace.com/pjimages/HarmonicPercolator.sch.png

Thanks,

Ryan

The answer to this depends on the output pot setting! At full output, it's probably around 50,000 ohms. At zero output, it's around 0!