Iv seen a few posts referring to a Scoop Mod for the Univox Superfuzz, seem to replace the switch with a tone stack? anyone got any info on this as it sounds interesting.
No. The Superfuzz has two tone settings. One is a fixed scoop, and the other bypasses the scoop filter, and subs a 2-resistor network to lower the level to approximately the same as with the scoop.
The scoop filter has a .1uf cap going to ground. If you insert a resistance between that cap and ground, it "lifts" the midscoop so that it isn't as deep. I've found that there's not much audible effect of that resistance being much higher than 6-8k or so. The major audible changes could be easily obtained with a 2k-5k pot. If you're able to render the midscoop essentially ineffective with that pot, then there is not much point in having the second "flat response" setting., though some may like it for reference purposes
Alternatively, here's an idea. The .1uf cap sets the corner frequency where the dip in the middle starts to happen; i.e., it helps define what "the middle" is. What if you wired up a smaller-value cap in parallel, like .022 or .01uf? Both caps would be connected at one end to the junction of the 10k and 22k resistors. At the other end, each cap would be connected to an outside lug of a 10k pot. The wiper of the pot would go to ground. Rotating the pot in one direction or the other would make the series resistance for one cap higher and the other lower. This would yield two different flavours of mid-scoop and variable midlift. I think I might try that out.
Thanks mate, stunning and really appreciated! :-*
OR replace the resistors with 50k pots. I have that on my breadboard currently with 4.7n and 47n caps. Lots of versatility. Sort of like Bass and Treble controls, but from the middle out rather than the ends in. ;)
Mark, do you, (or anyone else) know of a good reference that explains that kind of notch filter? My searches for technical info on notch filters always just returns twin-T circuits.
Simple, Easy Parametric and Graphic EQ's, Plus Peaks and Notches
GEOFEX has a nice article about notch filters. See above. :icon_smile: