Fulltone - OCD [traced]

[telecaster]

No problem Joe, I didn't take it the wrong way. I know you were just trying to help. This is a great sounding pedal.

[siore]

Hi siore, I built mine using Marks old layout to version 3 specs. I notice you have a 100r for R14 and Mark used a diode. I built mine with the diode and it worked fine. I wondered what that diode was for. I also used a jumper to correct the switching. HP was louder than LP, is that how yours is? I liked HP better, other than that I didn't notice any major tonal differences. I would build another without the switch. It did sound very good at 1-2 o'clock gain setting, past 3 o'clock the sound was more compressed, almost like a light fuzz sound. Very usable.. I gave that pedal to a stoner rock friend of mine and he loves it. I may have to make another one with your corrections, thanks.

I just went with the schematic where it's a 100r filter resistor. From what I understand, a diode can also be considered as a variable resistor, so I think it also works for lowering the noise floor at the power supply, which is what I assume the resistor is there for. Though I've etched the PCB's and sourced the parts, I haven't gotten to soldering yet. I'm also working on a rebote delay and some enclosures still curing, so it'll be some time. I'll take note of your observations, and see if I get the same.

[siore]

Ok I built it. Works ok, but the IC orientation is backwards, and so is the drive pot (attaching final layout). One mode (HP/LP?) is indeed louder than the other, but is less compressed sounding.

[Barcode]

Ok I built it. Works ok, but the IC orientation is backwards, and so is the drive pot (attaching final layout). One mode (HP/LP?) is indeed louder than the other, but is less compressed sounding.

I've built the original MarkM layout, the IC orientation is spot on... Mine worked fine on the first try, once I realized the tone knob needs that ground connection on lug 1...

[siore]

Yep I meant I didn't re-draw it right (IC orientation), but it's fixed now.

[Seiche]

okay i just sat down with the OCD again (that i built from the vero) and tried several variations of clipping. i can't really get it to sound good on chords and strumming. lead is really good, notes sustain and are cutting through really well. but the whole thing is a little too compressed for my taste and i would like to get rid of the fizzy-/sizzleness. does anyone have any idea how to achieve this? maybe it's not simply in the clipping stage but rather in the circuit itself??

[Seiche]

maybe i should add that i play an epiphone casino with p-90s and they have a lot of output.

[telecaster]

I find that the more i turn up the gain, the more compressed it gets. I keep the gain around 1 to 2 o clock, sounds more open that way.

[Barcode]

maybe i should add that i play an epiphone casino with p-90s and they have a lot of output.

Guessing that is most of your problem...

try tweaking R2 to a higher value, that will reduce the signal going into the opamp and maybe smooth out your issues. Then if you find a value you like you can put it on a switch and have a single-coil/humbucker switch.

[Seiche]

I find that the more i turn up the gain, the more compressed it gets. I keep the gain around 1 to 2 o clock, sounds more open that way.

yeah thats what i use max, but the sizzle already annoys me when i turn the gain down to 0

try tweaking R2 to a higher value, that will reduce the signal going into the opamp and maybe smooth out your issues. Then if you find a value you like you can put it on a switch and have a single-coil/humbucker switch.

thanks! i will give it a shot, maybe i should also try experimenting with diodes with higher forward voltages also, leds for example, instead of the mosfets to get more headroom? the maximum gain is much too much for me also, i prefer stacking lower gain ODs for more distortion.

Guessing that is most of your problem...

but they sound so great usually!

[Barcode]

I find that the more i turn up the gain, the more compressed it gets. I keep the gain around 1 to 2 o clock, sounds more open that way.

yeah thats what i use max, but the sizzle already annoys me when i turn the gain down to 0

try tweaking R2 to a higher value, that will reduce the signal going into the opamp and maybe smooth out your issues. Then if you find a value you like you can put it on a switch and have a single-coil/humbucker switch.

thanks! i will give it a shot, maybe i should also try experimenting with diodes with higher forward voltages also, leds for example, instead of the mosfets to get more headroom? the maximum gain is much too much for me also, i prefer stacking lower gain ODs for more distortion.

Guessing that is most of your problem...

but they sound so great usually!

Let us know how it turns out!

[Seiche]

hmm, i substituted a 10k resistor for R2 (i socketed it), not much of a change except maybe in perceived volume, but i'm starting to think there is really something wrong with my build. the fizzy decay is always present, it's exactly the same in duration (3-4sec) no matter where i set the gain (the gain goes up, but the fizzyness remains the same, it's hard to explain). It's there if i change the clipping diodes for leds, etc, or take them out completely. And no matter what i substitute for R2 (2k2, 5k, 10k).

the ic voltages on my unit are as follows (why haven't i checked them earlier ):
1. 7.31
2. 7.31
3. 6.99
4. 0
5. 7.31
6. 7.31
7. 7.31
8. 8.91

they seem weird don't they?

[Seiche]

it actually sounds very much like this (notice the fizzy decay when he lets the first chord ring out with the ocd engaged)

maybe that's normal, but i don't like it. anyone else have that problem?

[geiristudio]

Will this layout be able to run on 18v properly ?

[hbo]

Will this layout be able to run on 18v properly ?

If you use caps rated for 25v or more you should be fine.

[geiristudio]

Okay, thanks!

[geiristudio]

Hey one idea. I really like the low gain setting or the LP setting so I was wondering what to do to hardwire it at that setting and loose the switch ? I use the vero layout posted above.

Thanks in advance!

[bubstance]

You can just remove R12, swap R10 for anything around 13.2K and not bother with the switch.

[geiristudio]

You can just remove R12, swap R10 for anything around 13.2K and not bother with the switch.

Thanks man! I really appreciate it!

[ebuprofen]

build another OCD (like 5th or 6th ) and this one is oscillating have absolutely no idea what is wrong.
used the same pcb with every OCD I build, only in this one used 220p cap made by Wima, not SilverMica, the whole difference.
when GAIN is min, no oscillation, when raised a bit and to the end it start to squeal with high pitch.
replaced the GAIN pot, no difference, what could be worng?