DOD FX-17 overhaul

[benallison]

Ok, I got this volume pedal, DOD FX-17, for it's small size (pedal board real estate is at a premium).

There are a few problems with it though:

1) Volume only kicks in about halfway through the range of the foot pedal which is already pretty small. Any mods to give the pedal a true audio taper from toe right down to heel positions?

2) It's a little funky before overdrives and distortions, and while it adds no noise on it's own, it adds plenty with gain pedals in the chain. Any ideas if something can be dome about this?

I use the pedal for volume swells only, and addressing these issues will make it more useful. Thanks!

[ayayay!]

Look up Paul Morossy's stuff about that pedal over on www.diyguitarist.com

[benallison]

His site has great info, but all his mods concern the wah side... nothing about evening out the volume sweep range or helping it play with dirt pedals better 

[jayp5150]

Doesn't it have a maximum volume trimpot?

I'm going off of memory... I may be wrong.

[benallison]

No. The trim pots control the upper and lower frequency limits of the wah.

[letsgocoyote]

i just got one of these recently too, and i find the both sides of it lacking.  i'd definitely like to fix the taper!

[Paul Perry (Frostwave)]

I just had a look at the circuit ( a difficult to read .pdf, redrawn by Paul Marossy) and the two trimpots affect the control voltage that is derived from the footpedal section.
The resultant control voltage goes to BOTH the wah section (LM13700) and the volume section (CA3080).
For a rough hack, I'd increase the resistor going to the control pin (pin 5) of the CA3080. BE CAREFUL, if this pin shorts to + rail, it's fried. Do not decrease the resistor either.
The diode in series with it should affect the linearity of the volume as well, you could try putting another diode (maybe Ge) in series with it.
I'd like a link to a more legible copy of the circuit, if anyone knows of one.

[benallison]

Paul, thanks for checking the schem!

I wished I could makes sense of these concepts better...

I'll play with the trim pots and report back.

[Paul Perry (Frostwave)]

Just checked the pdf again & it is perfect, my computer (and myself !) were having problems. 
Note that the center frequency can be shifted up or down by changing the two .01uF caps hanging off the LM13700 sections.

[benallison]

Ok, I mucked around with the trim pots and they TOTALLY mess with the "volume" part of the pedal... which blows because settings that are ideal for the volume ramp are not ideal for the wah range – which defeats the purpose of having it be a 2-in-1!

Anyway...

So my volume issue is solved... the volume ramp is usable now.

Still, it adds noise when my dirt boxes are kicked in, but the tone doesn't change too much. I can get used to a bit more white noise; since I'm using it for ambient volume swells into a delay, a little noise really doesn't hurt, and sometimes actually sometimes helps. I guess I'll throw it in to a true-bypass loop when not in use for now.

I'm probably going to replace it with a George Dennis at some point...

Thanks all – special thanks to Paul for reading and deciphering the schem!

If any one still has noise-removing-tone-improving mods, I'm all ears!