Rodent vs Rat "fiilter" control issue

[6stringer]

Greetings,
I've built several Rat style pedals using the Rodent design from the GGG website and have noted that the "filter" control does not do much at all.   As a comparison, I've just built a "Rat" pedal, using the design layout from Tonepad and the filter control has a very useful range of tone shaping.   I see that the two circuits are slightly different but don't understand enough to discern how the differences actually effect the design or to know why the "filter" controls work so well in the "Rat" and hardly at all in the "Rodent".   I see that others here have noted the ineffectiveness of the filter pot in the Rodent too.  I might say that that although the "filter" is ineffective in the Rodent, it is still a really great sounding pedal, I would just like to make the filter control more usable.  Any ideas?   As always, I appreciate your advise and knowledge (and willingness to help us more nooby (noob-like?) builders.
R

[Mark Hammer]

I've used the Rodent board and it works fine.  The Rata board layout at Tonepad looks fine to me as well.  So there may only be a couple of sources of problem here:

1) You accidentally used the wrong cap value and are trimming /filtering frequency content that your speakers can't reproduce anyways (i.e., the filter control works, but in a range you can't notice).

2) The pot taper is incorrect and much of the filter control range seems to have no audible effect as a result (i.e., it only seems to "work" at one extreme).

3) There is an etching error and something is shorting or else remains unconnected, yielding no actual change in filtering no matter where you set the pot.

[6stringer]

Thanks for the reply Mark.   Both of the circuits call for a 100k-A pot going to 1K5 resistor, then a .003 cap to ground.   I substituted a
.0047 cap in both pedals and it works great with the Rata circuit.  Do you have a suggestion for another value (other then .003 or .0047)
that might make the Rodent more effective?    I've built 3 of the Rodent pedals, one with a JD Sleep ready-made board and two
that I made myself from the same layout (learning how to make PCBs).  All three boards have the same issue with the "filter" pot, so
it seems unlikely that I built all three with the same flaw (like a poor solder join, etc).   Will mesauring the output (voltage) from the pot
tell me anything useful?
Thanks
R

[Mark Hammer]

The utility of using a 3300pf cap or something different will depend on your taste, guitar, and amp.  In some instances, it may well require a 4700pf cap (or higher) to yield a noticeable change in treble content. In other instances, a 2200 or 2700pf value may be enough.

Whether it is "enough" or not, you should be able to hear a change in tone at the extremes of the Filter pot.  After all, it has a rolloff at 32khz at one end, and 475hz at the other.  That ought to be audible....unless there is some issue with the pot.  But as you note, the same thing shows up with all 3 builds, so it is unlikely that the same issue inpiot functioning would repeat itself 3 times...unless you moved the same 100k pot from one build to another trying to see if it would work there.

[Seljer]

I built mine on perfboard but based it off the Rodent schematic/layout and the tone control works fine for me from day one, not sure how different the actual PCB is (but i'll be finding out soon when part arrive it and I rebuild it on a real PCB)

though the first time I tried to build it (first pedal ever, urgh) I also built it on perfboard ended up with some kind of crazy layout that oscillated like hell (though I was using a TL071 instead at the time). As well as the gain pot being in the wrong way (can't remember if the tone pot worked though).

[wampcat1]

just for kicks, solder in a .047uf cap where you now have a .0047uf (and what the schem calls for .0033uf). If you don't hear a change in tonality after this, see Mark Hammer's #3 (above).

bw