wierd ring type thing... or Armstrong Green Ringer

[Scott Gravenhorst]

I have since deleted the thread, but the orginal URL:

http://www.ee.ualberta.ca/~charro/cookbook/audio/guitar/grnring1.gif

This is called an "Armstrong Green Ringer" by the inventor.  I can't
remember who it was, but someone wrote that it looked like a fullwave
rectifier, that is, assuming the "mystery part" is an NPN transistor
operating like two common anode diodes.  After much farting around
with it due to lack of exact components, I managed to make it work.
Or rather I made *something* work.  I used a 15 volt supply instead of
9 volts and I used 2N3904 and 2N3906 instead of the trannies called
out, so I had to change most of the resistor values.

For the "mystery part" I tried transistors I had laying around,
including MPF102 JFET.  These parts either allowed no output at all or
halfwave rectification.

However, using the EB junctions of two 2N3904 trannies or two common
cathode 1N914 diodes worked equally well as a fullwave rectifier,
verified by oscope.  When presented with a sine wave, the output
frequency is doubled and some extra harmonics are audibly obvious.

For what it's worth...


-- Scott Gravenhorst