I've got this bad boy working now but the reverse mod doesn't do anything. I feel pretty dumb because it seems simple enough but could somebody explain how to wire up that mod. Maybe I'm missing something.
http://www.tonepad.com/getFile.asp?id=5
Can somebody tell me what the dotted line means in the schematic showing the switching of the reverse mod? Does this mean G & H are always connected?
Thanks,
Bill
Hi,
the reversse mod is done by wiring a 2 pole double throw switch,you have to disconnect G and H, and connect the switch this way:
C--O O--D
G--O O--H
O----O
I hope you understand my ascii artwork :)
all the best
Maneco
Thanks Maneco,
That did it! This pedal just keeps getting better and better. Now on to the filter range mod. :lol:
Bill
Steve Giles asked me to post this on his behalf:
I can't post on Aron's forum from my laptop - please tell the guy that the reverse sweep mod is just passing the CV through an additional spare inverter on the 4069, (although I was using a 4049 at the time)followed by a pot to mix normal and inverted CV, nothing more, nothing less!
To this I would add the following:
The MXR-EF sweeps the filter by changing the mark/space ratio applied to the switch sections in the 4066.
Huh?
The effective resistance value produced depends on how much time the switch spends closed/conducting as opposed to open/impeding. As it spends more time closed, the effective/average resistance value drops.
What the addition of the invertor section does is simply reverse things, so that the switch is now told to close at the same point it would have normally been told to open. If it was closed 40% of each cycle and open the other 60% of the time, it is now closed 60% and open 40%.
Although the mod "works", in some respects EVERY sweep reverse needs more than a simple inversion to work optimally. Bear in mind that sweeping upwards rarely goes from the complete bottom of the range to the absolute top of the range. If you simply ask the filter to sweep from the top of its range downwards, you have no guarantees that it will sweep down far enough from the starting point to shape the frequency bands critical to the sound you want.
Even if it does sweep down far enough, when you start from the top of the range, that much sweep in that little time often sounds poor compared to the same amount of sweep going the other way. (Have a cat/kitten follow a quick hand movement upwards. Now move your hand downwards the same amount and speed. You'll find it "tracks" upwards movement very nicely, but is confused by downward movements, most likely because it is hardwired to notice birds and such leaping off the ground. Envelope followers seem to work much the same way.)
Ideally, every reverse sweep really needs to have a tunable start-point, and will probably need a sensitivity adjustment, so as to produce the appropriate amount/range of sweep for its given direction. The sensitivity adjustment is already built in. All that remains is to use a 3PDT toggle which could select a compensating resistor, or else some sort of tunable "start point", which the mark/space ration would be reduced/increased from.