Big Muff Pi Voltages

Started by azrael, January 20, 2010, 01:17:44 PM

Previous topic - Next topic

azrael

I was checking the voltages of a modified Big Muff Pi I did a while back, and noticed they differed from the voltages shown here:
http://www.generalguitargadgets.com/pdf/ggg_bmp_instruct.pdf

It got me wondering...Would it be tonally beneficial for me to bias the transistors on the BMP to a certain voltage? Is there a bias where the BMP performs/sounds better?

foxfire

probably not but hey that's what breadboards are for...you may find a sound you like better who knows?

petemoore

Would it be tonally beneficial for me to bias the transistors on the BMP to a certain voltage?
  Yepp.
  Nope.
  Or.
  Depends.
  Considering the transistors as contributors to the distortion, and/or that the diodes clip before the transistor gets to peak V swings, this can, of course, be tailored to taste.
  I think part of the idea is that plunked together with loose tolerances on components the circuit does the boost, boost-distort, boost-distort, TC, boost deal without worrying [for instance] about whether it's 10k, 12k, or 15k on the collector.
  Bias seems like it's designed to be less of a consideration in the BMP than say the FF.
Convention creates following, following creates convention.

mac

In all cases q1,2,3 collector is near 4v. No significant change in sound if you use 12k, 15k or 22k.
On the other hand, if you change coupling caps and resistors, clipping diodes' caps and tone stack parts you'll notice a big diference.

mac
mac@mac-pc:~$ sudo apt install ECC83 EL84

azrael

Okay, cool. Thanks for saving me the unnecessary work, guys. :)