Wah capacitor sweep range

[spoontex]

Hi,

I'm planning to build a wah with capacitor sweep selector. Like this RMC.



This use 9 DIP selector. What capacitor values I should use?

DIP 6: 5n6, 8n2, 10n, 15n, 22n, 33n

DIP 9: all 5n and combine them ( parallel capacitors )

What do you think?

[ElectricDruid]

Given that they're changing the frequency, I think the values need to be arranged musically; e.g. octaves or half-octaves or similar.

Adding 5n's in parallel gives a linear increase in capacitance, which isn't what you're after.
5n to 10n goes down an octave. 10n to 20n (two more caps) goes down another octave. Then *four* more caps are required to go down the last octave.

4n7, 10n, 22n, 47n is a rough sequence of octave values, the E3 series.
If you add in E6 values, you get something like half-octaves:
4n7, 6n8, 10n, 15n, 22n, 33n, 47n.

HTH

[spoontex]

Given that they're changing the frequency, I think the values need to be arranged musically; e.g. octaves or half-octaves or similar.

Adding 5n's in parallel gives a linear increase in capacitance, which isn't what you're after.
5n to 10n goes down an octave. 10n to 20n (two more caps) goes down another octave. Then *four* more caps are required to go down the last octave.

4n7, 10n, 22n, 47n is a rough sequence of octave values, the E3 series.
If you add in E6 values, you get something like half-octaves:
4n7, 6n8, 10n, 15n, 22n, 33n, 47n.

HTH

awesome!! thanks.

and the fine tune? what the hell is it?

I found this on the Analogman website:

FINE TUNE - The two trimmers (5th & 6th) let you subtly fine tune the primary SWEEP DIP settings.
Turning the trimmer to line up with the "leg" (solder point @ 9:00) adds bass. Turning the trimmer to the
3:00 position adds treble. While these tuners can be turned 360 degrees, only the half-turn from 9:00 to 3:00
is required to make the transition from bass to treble.
SWEEP - The 9 pole DIP switch expands or compresses the sweep range of the RMC3. The switches are set
up in a sonic progression. Switch #1 equals the maximum sonic value of FINE TUNE. Switch #2 is the sonic
equal of Switch #1 and FINE TUNE together... and so on. This overlapping stairstep sequence lets you select
the depth and width of the RMC3's actual frequency sweep. The higher the number switch(es) selected, the
wider and deeper the sweep will be.

But I don't konw what exactly do this two trimmers.

[ElectricDruid]

No, I don't know.

Six trims on a wahwah is pretty wild. There's only a handful of parts in the whole circuit, so about a third of them must be trimmers!

I'd have a look at the standard Crybaby inductor wah circuit (assuming that's what this is based on) and then see what they might have made variable. For that "fine tune", there can't be many options.

[spoontex]

No, I don't know.

Six trims on a wahwah is pretty wild. There's only a handful of parts in the whole circuit, so about a third of them must be trimmers!

I'd have a look at the standard Crybaby inductor wah circuit (assuming that's what this is based on) and then see what they might have made variable. For that "fine tune", there can't be many options.

I totally agree with you. I asked only for curiosity.

Thanks.