So I had last FX-X entry
(Modzky)`s prototype breadboard still lying there,
which actually had come forth from trying to de-crackle a certain (in-)famous boostortion, now abandoned,
when I thought: hey, before tearing it apart, let`s look what`s up with that other
(MarkM`s "Buckaroo") entry,
which could easily be breadboarded out of half of that modulation circuit,
although I don`t like building other people`s circuits...
Ripped out half of the circuit, swapped the BC550 (BJT) for a BF245 (FET) I had on hand,
replaced the fixed collector-resistor with a pot, and hooked up scope and amp again.
Nice ~10 x boost (@ 1M load), after the (crackling) appropriate "bias" (drain voltage) was found.
Wait: what happened when I accidentally touched the grid and another wire:
the sound went away, and didn`t come back.
It did come back slowly however, when I touched the grid again, while also touching the strings
with the other hand...
(it could also be brought back by several times rotating the pot, while it was more difficult now
to find the sweet spot).
hmmm: what`s that? floating volume control?
yes: when touching positive voltage and grid the drain voltage went one way,
when touching grid and ground, it went the other way.
Would stop moving, when letting loose.
What does the
schoolbook have to say to this phenomenon? Nothing.
But it was evident, that this grid was sensitive to "static" charges.
Looking further in the book,it seemed that
Fig.10 was close enough to try for a cigar:
and: yes, out came "The €-DE-FLOATER":
in form of an extra resistor between grid and ground.
No more runaway of the drainvoltage due to environmental influences...
(4M7 can be used for that extra resistor and the pulldown one, to stay on the high input impedance side...).
Thanks for the inspiration!
