Cheap OD pedal to Fuzz ?

[Guytone64]

Hi, I have an inexpensive OD pedal which I never use now (Fame UCD) and I was wondering if there are a few mods I could make to turn it into a decent Fuzz pedal ? I'm guessing (perhaps wrongly ?) that many of the components of an overdrive and a fuzz are common to both so is it just a matter of swoping out a couple of bits here and there ? Any help gratefully received as I know next to nothing about electronics !

Some photos attached to show the outside and inside . . .

Cheers

Fame UCD

Inside Fame UCD

[Ichabod_Crane]

Joyo JF-02. It should be a Fulltone OCD clone.
We have to try turn it into a Fuzz. I'm sorry, but I don't know how we could. Maybe changing the clipping and the amount of gain?

[thetragichero]

http://zadvitsky.com/index.php/projects ... e-diy.html

goes through the ocd circuit. component numbering is probably different

I'm still learning the actual electronics behind it all, but as somebody who learns from tweaking things i would try:

changing the clipping mosfets/diodes to leds to try to slam the second op amp stage. changing the c7/68nF cap to allow more bass through (my assumption is increasing the value, but i could be mistaken. something like 100nF lowers thecutoff frequency to around 700hz)
add anti parallel diodes inn the feedback loop of the second op amp stage (I'd use leds), change r10/150k to 470k, change c9/220pf to 150 or 100pf).... hey this is almost looking like what i enjoy for an op amp big muff!

cool thing is that this is a relatively inexpensive pedal so even if you screw it up it's not like you ruined something rare or vintage

have fun modding, otherwise why bother!

[Frank_NH]

http://zadvitsky.com/index.php/projects ... e-diy.html

goes through the ocd circuit. component numbering is probably different

I'm still learning the actual electronics behind it all, but as somebody who learns from tweaking things i would try:

changing the clipping mosfets/diodes to leds to try to slam the second op amp stage. changing the c7/68nF cap to allow more bass through (my assumption is increasing the value, but i could be mistaken. something like 100nF lowers thecutoff frequency to around 700hz)
add anti parallel diodes inn the feedback loop of the second op amp stage (I'd use leds), change r10/150k to 470k, change c9/220pf to 150 or 100pf).... hey this is almost looking like what i enjoy for an op amp big muff!

cool thing is that this is a relatively inexpensive pedal so even if you screw it up it's not like you ruined something rare or vintage

have fun modding, otherwise why bother!

I would just change R11 from 39K to 3.9K in the second op amp stage. That ought to make it good and fuzzy. It may also cause it to squeal, in which case you could modify the capacitors in the second stage to roll off some high end. Good luck and let us know what works!

[Guytone64]

Folks, thank you very much for your input here ! As I said earlier I understand little or nothing about electronics but I can use a soldering iron and I'm willing to give anything a try, even if it's just to learn from my mistakes ! So in theory it IS possible to change out a few components and end up with something Muff / Fuzz like ? I'll have to do some more research to find out what bits I'd need and where to source them but as was rightly pointed out the worst I can do is ruin the current PCB but I'd still be left with the enclosure, switch and buttons so no great loss

If anyone else out there has any suggestions / advice and the time to reply I'll be happy to hear from you.

Cheers

[Guytone64]

[/quote] I would just change R11 from 39K to 3.9K in the second op amp stage. That ought to make it good and fuzzy. It may also cause it to squeal, in which case you could modify the capacitors in the second stage to roll off some high end. Good luck and let us know what works![/quote]

OK, I found the famous R11 (magnifying glass was useful here !) and thankfully it seems quite accessible. Where would one find the capacitors in the second stage please ?

Anything else I'd need to do or is it as simple as just changing these 2 parts ?


Ta

[thetragichero]

when I'm working on a clone of a famous pedal, i print out the schematic (like i linked in the first post) and relabel the components with the numbers from the clone
r11 is 39k (from memory, driving down the highway), so look for a resistor that is orange white orange

[Frank_NH]

I should note that my reference to R11 was based on this OCD schematic:

http://zadvitsky.com/index.php/projects ... e-diy.html

Also, 3.9K is just a starting point - you could socket the resistor and try different values. If you're modding your pedal by desoldering the existing parts and soldering in new ones, you may have trouble if you want to swap parts in and out multiple times given the fragility of circuit board traces.

If it were me ,I'd breadboard the circuit first, make sure the mods were what I wanted then modify the pedal. Of course, if this is just an experiment and you're not worried about the pedal, then go for it.

[Guytone64]

Thanks Frank, I need to study electronics 1.0.1 this weekend to figure out all these parts etc because it all pretty new to me. I've changed caps on my guitars but apart from that I know next to nothing about how these things work !

Eugene

[roseblood11]

One idea: Add a switch that disconnects the Mosfets from Vref. The second opamp will do the clipping now. Try different opamps, maybe OP275 (as in the Black Cat OD-1 "Freddie Fuzz"), AD712, rail-to-rail models or very old ones like 1458. But first, replace the opamp with a socket...

[thetragichero]

maybe it's just the circuits I've run them in (my own paste ups of popular circuit blocks), but i LOVE the way old op amps (1458, 2904, etc) clip. only issue i run into is that they seem to eventually decide that being slammed with the V+rail is not cool so they stop amplifying.