And... Eureka!
One of the things that folks don't like about the Vox Pathfinder is the usability of the drive "channel". Turn it on and you more distortion than overdrive. To the point where, if Google is fact, the "LED mod" is the most popular mod on Pathfinders: where the LEDs that are used to clip or distort the signal, are removed.
I don't like the default distortion effect and have been looking for a middle ground: to have more adjustment in the gain control between high gain clean, crunch, and distortion.
I think I have found my middle ground. YMMV.
The combination is the following:
1. Swap the volume control for an audio taper pot, replacing the factory linear taper. "Part is Parts" has the right one that will fit the factory chicken head knob.
2. Solder a 1M resistor in parallel with R7 to reduce the gain in the second stage pre-amp. This gives more adjustability to the gain pot.
3. Increase the clipping voltage of the LED pair.
For #3, LEDs apparently clip at 1.6V or more (I've not managed to measure myself, but if Google is fact...). So the trick there, if you want to have more adjustability in the gain control and therefore more headroom, is to add more diodes in series with the LEDs to increase the clipping voltage.
My choice was a pair of germanium diodes which I got from Frys (part number NTE110MP). They had about 230+mV (measured) in clipping voltage. So putting them in series would increase the clipping voltage by that much. For even more headroom, one could use another set of diodes in series or a silicon diode.
Anyway, in addition to the germanium diodes, I added in a 220pF cap in parallel. This is, in theory, supposed to removed some of the high frequency fuzz. Not really noticeable, to my old ears, but the 220pF value was chosen because I thought the original 100pF I used didn't work that well.
Finally, I added a 100ohm resistor in series with the LED+diodes+cap. This is supposed to mellow the effect.
The outcome of all these changes is a much more usable drive mode. More crunch and a very marked reduction in fuzz and fizz.
Pics of the mod are attached.
IMHO, this is better than removing the LEDs all together as you still have an option to go all out in metal distortion mode.
I'll be putting everything back together again and using this over the next few days.
EDIT: Put in lower res pics