replacing cheap DOD switch with a real one?

[vseriesamps]

Hi everybody

I do a lot of geeking out with my DOD FX52 Classic Fuzz. I've had a lot of luck improving the tone but brightening the pedal, inserting a lopass filter or changing out the diodes.

Is there any way to replace the cheezy, cheap black plastic switch with a real one, like a switchcraft or something? Clearly it would have to be moved to another box. I don't understand the circuitry of this type of switching.

Thanks all
K

[SnooP_Wiggles]

Sounds like you want to do a true bypass mod. steps:

1. wire the circuit to be 'always on'
2. get a 3pdt switch. put everything in a new box (drill holes etc)
3. wire it up
4. done!

Sorry but i got no idea about the finer details.

[travissk]

Awesome pedal . You might want to read my last paragraph first for an easier option that involves roughly the same cost but much less effort.

But to answer your question, sure - Boss/Ibanez/Dod pedals of that type use FETs (Field Effect Transistors) to accomplish their switching logic. Good for producing pedals in massive quantities, but some people don't like the quality of the switches.

It's certainly possible to replace the switch: what you have to do is find a Dod schematic for that range of pedal. Avoid the old mechanical switching ones (250 overdrive, 440 envelope filter), and if possible avoid the newer style of switch. The new style might still be ok, however, as the circuitry should be similar. If that's the case, FX-anything should be ok. Here are two distortions on the site:
http://www.diystompboxes.com/pedals/dodfx53.jpg
http://www.diystompboxes.com/pedals/dodfx69.jpg

Then what you want to do is isolate out the buffering and switching part of the circuit. I haven't studied dod schematics extensively, because the ones I've been really impressed with (Juice Box and Classic Fuzz) don't seem to have schems out.  However, just by noting the similarities, look at the area that's separated out and in common. I'll use the FX53 schem because it's a little easier to read (smaller).

The area is located to the right of the schematic, 2/3 of the way down the page. The upper-left mini-circuit is just set up as a voltage divider for supplying V+ and (V/2)+, and the big circuit is then obviously "the effect."

Just in case you find another schem somewhere, here's a basic analysis: The basic switching logic uses that transistor with 10/11/12 markings to either allow current to flow or not allow current to flow. If that switch is not closed, then you have V+ going to a resistor and then to one terminal, the "gate", of the FET. Now, ideally no current may flow into the gate of a FET, so there is no voltage drop across the resistor. When the switch is closed, then the gate terminal of the transistor ("10") will be at ground.

I'm getting way too far into this just to answer the question (sorry!) but when that switch is connected to ground, the transistor will be "off" and when it's not the transistor will be "on". Therefore, we've found the switching part.

Now -this- part of the circuit ends ata node labeled "x", which is also present in the big circuit (top middle of the big circuit, bottom middle of the big circuit). The voltage at x will make the transistors Q1 and Q2 be either on or off. It looks like if Q1 allows current to pass, then the effect will be clean, and if Q2 is on, then you'll get that great fuzz.

Sorry if all that was background info that you've covered in an EE course or seen in other schematics

Basically: that little circuit will choose which path your signal takes, and you're going to get rid of that section of the circuit and replace it with a switch, preferably 3PDT. There are a lot of good articles on how to wire 3PDT's around here (link escapes me at the moment ), so you can use that to connect the effect up. I think you can short the connection handled by Q2 and open circuit the one that Q1 handles (you'll be true-bypassing your signal). I've never done this, so I can't comment on what to do and what not to do (everything has those pesky consequences), but essentially you'll treat what's left of the circuit as a complete effect that you can true-bypass.

That's for the Classic Tube overdrive. As for the fuzz, it might be hard finding which part of the circuit is the switching logic. However, just follow the leads from the switch and hopefully you can find X, Q1, and Q2.

Once you've found everything, hopefully the other forum members can tell you the best way to actually bypass the circuit.

Good luck!

-------------------------
Note:

As long as you plan on buying another box and a switch, I'd suggest buying two jacks and possibly another LED and simply making a true bypass loop box. You can leave the classic fuzz on all the time, and you won't have to tear up your existing pedal. I know they're cheap, but if it breaks due to a fall or something, you can just replace the pedal in the loop box and keep on going, rather than modding another one.

The downside is that you have another box on your board (it can be pretty small), and the Fuzz will always be draining current. Even if you use batteries, this shouldn't be much of a problem since the fuzz probably doesn't drain much current anyway.

[vseriesamps]

Wow, a forum where people courteously and quickly respond to relative newbie posts in great detail. Excellent resource!

I'll give all this a whirl - gotta order that switch - and let y'all know how it goes.

Keep it up!
K