Author Topic: Modding the DOD FX 52  (Read 148 times)

bifurcation

Modding the DOD FX 52
« on: December 05, 2018, 02:34:49 AM »
Hey all,

I'm a super noob to modding, but I've just dug up a DOD FX52 and am thinking of tweaking it into a more interesting pedal.

I've dug through every FX52 thread I can find, but most of them are pretty vague or are using a different layout than what I see in my pedal.



In general I think it would be fun to make the pedal more extreme and noisy, perhaps with a more pronounced midrange and bass.

I think I've figured out that the diodes near C6 are the clipping diodes. I was thinking of swapping those out for LEDs, but I'm also trying to to figure out how to wire in a switch to maybe swap out the tone capacitor between bright and wooly and I thought it would be cool to add an oscillation switch and try to add a "dead battery" pot to give the option to make it more "splatty."

I'm a little in over my head, but I'm hoping folks might have some advice to tweak the FX52 into a noisier, weirder pedal.

Thanks!

bifurcation

Re: Modding the DOD FX 52
« Reply #1 on: December 05, 2018, 02:50:22 AM »
... I mean in general, I'm wondering if one could both add some more quality parts while dialing up the nastiness of the FX52. You know, to drift it into DOD Carcosa territory and maybe add the chaos of the Fuzz Factory "stability" control.

bluebunny

Re: Modding the DOD FX 52
« Reply #2 on: December 05, 2018, 02:59:00 AM »
add some more quality parts while dialing up the nastiness

It's a fuzz, not hi-fi.  :icon_twisted:  Expending effort on swapping in "quality parts" would be a waste, imho.  It's like putting gold-plated handlebars on your Harley: it's still gonna fart like an ox...  (And is meant to do so!)
Ohm's Law - much like Coles Law, but with less cabbage...

bluebunny

Re: Modding the DOD FX 52
« Reply #3 on: December 05, 2018, 03:01:17 AM »
BTW, here's a schematic.  Might help with ideas...

Ohm's Law - much like Coles Law, but with less cabbage...

bifurcation

Re: Modding the DOD FX 52
« Reply #4 on: December 07, 2018, 03:57:08 AM »
Thanks Bluebunny!

I really can't overstate my ignorance with modding pedals.  :-\

I'm assuming these are the clipping diodes (and this is where they are on the board.) Maybe I'll just unsolder these and try out different stuff (LEDs, etc...)


I wish I could figure out what these missing diodes are for:



I heard DOD used the same board for some different pedals, I'm wondering what adding parts here would do?

bluebunny

Re: Modding the DOD FX 52
« Reply #5 on: December 07, 2018, 04:49:15 AM »
Yes, I think you've spotted the clipping diodes.  It's a little difficult to work out when you can't see the underside of the board (except through the top), and everything is very spread out, so co-location of components only goes so far.

I would say that the empty diode slots are for clipping in the feedback loop of the first half of the LF353 (they appear to be in parallel with the 3M9 resistor).
Ohm's Law - much like Coles Law, but with less cabbage...

bifurcation

Re: Modding the DOD FX 52
« Reply #6 on: December 07, 2018, 01:47:51 PM »
I would say that the empty diode slots are for clipping in the feedback loop of the first half of the LF353 (they appear to be in parallel with the 3M9 resistor).

Ohhhh, cool. Maybe I'll try wiring some diodes/LEDs and see what that does.  :)

bloxstompboxes

Re: Modding the DOD FX 52
« Reply #7 on: December 07, 2018, 05:55:09 PM »
The FX52 is actually the same circuit as the classic tube, Supra distortion, and one other i think that escapes me now. I did one a couple years ago and really like the classic tube for a bit. They just changed some values here and there. I put up a layout here then too, but left out a resistor or cap by mistake. Easy to add in though.

Here it is: https://www.diystompboxes.com/smfforum/index.php?topic=112861.msg1042992#msg1042992

As stated there, I recommend a toggle for symmetrical and asymmetrical clipping.

Floor-mat at the front entrance to my former place of employment. Oh... the irony.

bifurcation

Re: Modding the DOD FX 52
« Reply #8 on: December 07, 2018, 06:46:51 PM »
Awesome, thanks!

bifurcation

Re: Modding the DOD FX 52
« Reply #9 on: December 08, 2018, 04:43:44 PM »
Another stupid question...

Studying the boards for the FX52, FX53 and FX55, I see that the little diode area on the bottom of the board is used on the FX53 and FX55 (thanks again Eric for the dropboxes with the schematics,) but not on the FX52.

So, the dumb question: I guess I always assumed that more inverted diodes means more distortion/fuzz. No? I always assumed the Classic Tube and Supra were mellower pedals than the Classic Fuzz?  ???

bluebunny

Re: Modding the DOD FX 52
« Reply #10 on: December 08, 2018, 05:19:31 PM »
Those empty diode positions are in the feedback loop of the first LF353 opamp.  They will begin to conduct at their forward voltage, VF.  When they do this, they're like a dead short.  And a dead short in an opamp feedback loop gives a gain of 1, i.e. no amplification (aka. a buffer).  So for some of the time (i.e. some of the waveform), the opamp isn't amplifying, so it doesn't sound extreme or loud or ...  Let's call it "mellow".  :)

The behaviour of the diodes at the output of the opamp (which is where the other ones are installed) is quite different.  And somewhat "harsher".
Ohm's Law - much like Coles Law, but with less cabbage...