Fulltone - OCD  [traced]

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evaninsky
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Post by evaninsky »

I'm confused and could use some help....

I built an OCD based on ver. 4. It's AWESOME but I'd like a bit more high end sparkle. it seems that Fulltone changed the volume pot from 100k to 500k (ver.1 to ver. 2) and the cap from .1mf to .047mf (ver. 2 to ver.3)

they report that both these mods result in softer highs and more mids. doesn't lowering the tone cap's value increase the highs or do I have it backwards ?

I'd like to restore a bit of the high end... which (or both) of these changes should I restore ??

please help guys !!

BennyB
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Post by BennyB »

BennyB wrote: Some voltage measurements: (with the chip out)
Battery: 9.2
Pin 1: 4.15
Pin 2: (with the drive all the way) 4.15
Pin 3: 4.39
Pin 4: 0
Pin 5: 4.15
6-
7-
Pin 8: 9.2

Sorry to pester, but are these okay voltages?

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Seiche
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Post by Seiche »

hey,

i just build an ocd from the vero layout above. The Volume and Tone Pots work, though the volume is not "lots" more when i turn it up all the way.
What concernes me is that the drive knob doesn't do anything at all. I don't get any grit, just a clean boost. What could be the problem? I tried troubleshooting it with the schematic (i tried to exchange drive 1 & 3, as in the schematic it is noch really clear which is which) but no luck.

Has any experienced something similar?

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Post by Seiche »

nevermind, i went over all the solder-spots and cleaned the vero strips as to not accidentally connect one to another and it works now! [smilie=a_goodjob.gif]
I haven't tried the real thing (same with the Tubescreamer i built the other day) but I am really impressed! that thing screams! I like the LP mode better for now.

cheers guys [smilie=18_13_1.gif]

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Post by Seiche »

Okay now after some testing and twiddling, i have one thing that annoys me.
My favorite setting for a nice crunch is the LP mode with gain and tone roughly on 10-11 and the volume on 2 o'clock. But whenever i dim the gain all the way i get this very slight bit of grit creeping in. Now i tried to fiddle a bit with the clipping stage and took out the ge-diode (no dicernible difference) took out one of the jfets and put the ge back in (a little cleaner, still that bit of grit), put an LED inplace of the ge-diode (no dicernible difference), took out both jfets and the diode, still the same sound as before.

what's going on? maybe i made a mistake wiring up the veroboard?

hakanenlauri
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Post by hakanenlauri »

Hi there everyone.

I recently undertook a couple of new projects one of which is the Stratotrasto version of the OCD (Rev 4). I have now bread boarded it but have some issues with it. First and foremost, when the drive pot is all the way up (-ish), the distortion gets this very stuttery tremolo-like quality. Also, the volume pot doesn't really add that much volume to the sound as opposed the bypass sound. And, pulling one of the transistors (or both) out doesn't have any effect on the distortion sound. Shouldn't it?

Any ideas on this?

Thanks in advance,
Lauri

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Post by RomYch »

Hi guys!
Here's my OCD:
OCD_lay.jpg
OCD_sch.PNG
http://ifolder.ru/21647572 - LAY in Sprint-Layout 5.0
I slightly modified scheme. Added output buffer and the millennium bypass.
Now this is my favorite device!!! :D

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Post by siore »

Hi y'all.. if you're like me who's following the thread holding markm's layout together with tuemmueh's schematic... I thought this might help. I basically re-drew the layout. Values indicated are the ones on the schematic, I flipped the mosfet orientation, and... the resistors on the HP/LP switch I put in parallel.



Cheers!

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Post by siore »

Made a mistake in the re-draw, noticed it as I was drilling :slap: . Power supply pin on the IC was left hanging. Also cleaned up a little, some traces are too close for comfort. Sorry about this, I'll PM the mods to have the wrong one removed.
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telecaster
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Post by telecaster »

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.
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Post by joeboo88 »

Hi telecaster, the pcb layout is different layout from the vero i used a few months ago, mine sounds like the you tube videos of the OCD.
(I'm Not bragging, actually i was amazed i got it to work first try)
I think there are a lot of variations to this layout, sorry to add to the confusion.
When i built mine i read the whole tread, because that helped me learn what i can expect with each version and what possible mods there was (at The Time).Also what problems other guys found while building.
I think i read somewher that the LP was supposed to be quieter than the HP. I accepted this and this proved right when you watch the
videos. One the video'rs Andy from proshopguitar video said that the LP was supposed to imitate a fender amp, and the HP was supposed to emulate a Marshall. I dont know if i believe that but what the hay.
You should read the thread and and look at all the schematics and layouts then decide which one to use.
Good luck :D
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Post by telecaster »

Hi Joeboo, I'm well aware of the other versions of this circuit, that's why I built it to V3 specs. I like the sound of that version best.
I have also read this entire thread, and referred to it many times, good advise though.
My post was simply to express my experience and observations with this circuit. I think it sounded great and plan to build another just like it, without the switch next time. :)
KindaFuzzy - Looks like a blue nail polish and nutella sandwich.
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joeboo88
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Post by joeboo88 »

Hey telecaster, after i wrote this, i reread your post and realized you probably did all that, sorry.
Anyhoo, good luck with the new one...I like using this pedal a booster, gobs of volume. take care 8)
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Post by 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.:thumbsup
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Post by siore »

telecaster wrote: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. :thumbsup

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Post by 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.
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Post by Barcode »

siore wrote: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...

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Post by siore »

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

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Post by 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??

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Post by Seiche »

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

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