Fulltone OCD versions and mods:
http://fulltone.com/PDfFiles/OCD%20complete%20Mods_small.pdf
Official file from Fulltone site...
regards, Jack
Where's the goop??
sometime in september 2006 jhs wrote...
Quote
For a 100k pot for volume the tone pot should 10k and 10-33n, for a 500k pot for volume the tone pot should 100k and 33-100n.
If the tone control on the OCD (100k/100n w 100k for volume) is set to zero the tone is very dull and for me nearly useless.
??? learning by doing or learning by listening ah reading!?!
oh, and the recomentation for the 10k pot + 33n cap was for the 100k vol pot. :icon_rolleyes:
does anybody of you guys know when the seriell #9474 passed?
and by the way I don't think that the 1m gain poti will sound that good.
cheers
ghandi
I played that pedal..and let me tell you that a thousand of the od posted on this forum are 1000 times better..that one sucks
Now, that everyone knows that it's a slightly modded VL OD there is no reason to goop it any longer.
This third version mod was developed by a FX-modder and published in another forum a few month ago.
The same with the 500k vol mod for the 2nd version.
I like the first version better, way more open sounding and IMHO V1 is much better for clean boosting and light crunch. The third version is a real mid humper with reduced high and bass end and IMHO not good for boosting a clean sounding guitar or for light crunch.
I don't recommend to change the vol to 1M, w the 1M it sounds more like a fuzz pedal when maxed and very compressed and furthermore the 1M makes it hard to dial in gain nuances when the gain is set low.
When the tone pot (it's a simple guitar tone control wired to the vol pot) is closed the sound is IMHO dull and useless and a small R in series with this pot is a good mod to prevent this effect.
JHS
Quote from: JHS on January 05, 2007, 07:48:48 AM
Now, that everyone knows that it's a slightly modded VL OD there is no reason to goop it any longer.
Hi, sorry for the noob question. Does VL OD mean Voodoo Lab Overdrive?
Dave
Quote from: 96ecss on January 05, 2007, 08:12:19 AM
Hi, sorry for the noob question. Does VL OD mean Voodoo Lab Overdrive?
Dave
Yes
Hi JHS, just two questions.
1. Looking at original mods pdf photos, it seems the clipping section is realized with 3 MOSFETs (for a classical asymmetric distortion). Is it a right supposition?
2. In the photos I see also two 1N400X type diodes, one on the left (probably for supply polarity protection), one on the rigth. Do you know the use of the right one?
VL=Voodoo Lab
The 2nd diode (any Si-diode like 1N914/4148/... will work) and the 3rd trannie belong to the LED-circuit. The led is wired in series with the collector R of the trannie and the footswitch shorts the LED when the FX is in bypass mode.
JHS
This is quite an interesting thread, I was under the impression that the OCD was an original circuit developed by Mike Fuller.
So the OCD pedal is in fact a VooDoo labs pedal?
Are there links for the circuit diagrams etc?
Do you suppose Mike Fuller is a member here?
Yours Sincerely
Mark Abbott
Hey Mark!! i know you from the trainwreck and d*mble forums. I have that schem...can't remember the link i got it from...but can email it to you if you want.
Here's a link to the VLOD schem.
http://www.freeinfosociety.com/electronics/schemview.php?id=1208
ooops, hit the wrong button... wrong reply thread... :icon_eek:
Quote from: Mark Abbott on January 06, 2007, 05:26:57 AM
This is quite an interesting thread, I was under the impression that the OCD was an original circuit developed by Mike Fuller.
So the OCD pedal is in fact a VooDoo labs pedal?
Are there links for the circuit diagrams etc?
Do you suppose Mike Fuller is a member here?
Yours Sincerely
Mark Abbott
Word around the grapevine says Mike does browser through here a bit. :)
I can't think of one fulltone pedal that has been an original design, no disrespect to Mike - he's very good at marketing! :)
Honestly though, 95% of the "boutique" builders (is there really such a thing anymore?) are just building modified versions of existing pedals and to be fair, there isn't much that hasn't bee tried in some shape, form, or fashion in the distortion/overdrive/fuzz arena. I mean, there's only so many ways to skin a cat. :)
bw
Quote from: wampcat1 on January 06, 2007, 03:35:20 PM
I can't think of one fulltone pedal that has been an original design, no disrespect to Mike - he's very good at marketing! :)
Agreed but with all the bad things you can say about Mike and his product designs the one thing he still does that other builder still don't do very well is making the pedal tough. Tour worthy. I give him credit for that alone.
Andrew
Quote from: JHS on January 05, 2007, 07:48:48 AM
Now, that everyone knows that it's a slightly modded VL OD there is no reason to goop it any longer.
Not doubting that it is a tweaked VLOD, but if you count the caps and resistors seen in the ungooped pictures, there are a few more parts in the OCD than in the VLOD, even if you count the HP/LP switch and associated components, and the tone control and cap. Also I built a VLOD and it sounds nothing at all like the OCD; the clarity of the OCD is staggering. I strongly suspect the OCD has some more stuff going on in there. Also there do not seem to be any series diodes with the MOSFET clippers. It sure would be interesting to see a schematic though...
Here's my VooDooLabs OD vero layout from early 2005 from Justins schem:
http://aronnelson.com/gallery/Martys-layouts-and-photos/VooDoo_Labs_OD?full=1
Gain should be a 500k ( all I had ten were 470's )
It's a cracking little OD circuit,
Mod away !!
Marty.
I would like to know which Mosfets are being used. I have tried almost a dozen and they all sound different. Different clipping thresholds, capacitance, transconductance, etc.
I don't know, but he may be using the second method posted here at AMZ. It works well with a low threshold Mosfet, but the std. BS170/2N7000 clipping threshold is a little high. The IRF510 is even higher, potentially maxing out the op amp first???. http://www.muzique.com/lab/zenmos.htm :icon_cool:
I don't know the OCD circuit, but it seems a little bit different. From the mod page if changing the gain pot to 1M gives more gain then that tells me that the pot is in the feedback loop, and not hanging off of the inv input. If it was set up like the VL then a 1M pot wouldn't increase gain - it would lower it at the lowest settings. Just a guess.
Later, PaulC
Quote from: MartyMart on January 07, 2007, 09:32:30 AM
Here's my VooDooLabs OD vero layout from early 2005 from Justins schem:
http://aronnelson.com/gallery/Martys-layouts-and-photos/VooDoo_Labs_OD?full=1
Gain should be a 500k ( all I had ten were 470's )
It's a cracking little OD circuit,
Mod away !!
Marty.
Thanks for the layout, that's the one I built. I made some of the mods listed here and elsewhere to try and get the clarity of the OCD, no luck. Also, that would make sense what WGTP posted, the second clipper in the AMZ article; nice and simple and does the job with no series diodes. The main problem to my ears with the VLOD is the lows seem artificially clipped along with the highs (not too fond of that sound). Maybe the OCD has some sort of frequency dependant clipping, maybe clipping the highs while leaving the lows relatively unclipped. I was going to try adding an additional 4.5v divider for the clipper voltage reference and using a smaller bypass cap to roll off the clipping at lower frequencies.
Then again, maybe the OCD simply isnt a VLOD knock-off :icon_question:
So far we have had people insisting that its a TS, a Dist+, a Sparkledrive, a VLOD etc etc etc with absolutely nothing to confirm the claims. Until someone I trust comes up wth either ungooped pics of comp&trace, and a schematic, Im not holding my breath. I have no doubt it is a modded <whatever>, but as I didnt like the one I tried out I can wait.
Comparing the schems, the OCD is 90% VL OD and 10% mod (some part values, Gain control and RC-network is similar to the FD2).
The type of mosfet has nearly zero influence on the sound, only the internal protection diode is used for clipping. It's not the AMZ- or Mosferatu method, there are no additional diodes, the 1N914 are replaced w mosfets, that's all. The diodes clipp only at high gain levels and add some compression, you can leave them out at low gain (the dynamic range is better w/o diodes). Most of the sound and character is generated by the TL 082 chip, its the crucial part and the tantalum caps produce the clear highend and raunch.
All in all I woul'd not call it overdrive, it it nearer to a good distortion.
There's a lot room for improvements. The reaction to the guitar vol is quite bad like on the VL OD but this can be cured with a LPB-1 or other similar booster set to unity gain in front of the OCD.
JHS
hey jhs,
i allways wonderd what that little caps are?
do you think that are tantalums?
i thought that might be high quality ceramic caps!?
oh and on an old mod side mr. f told to replace the 100n cap in the fb with a 47n mylar.
cheers
ghandi
Quote from: The Tone God on January 06, 2007, 04:18:47 PM
Agreed but with all the bad things you can say about Mike and his product designs the one thing he still does that other builder still don't do very well is making the pedal tough. Tour worthy. I give him credit for that alone.
Andrew
Anymore I think the most interesting aspects of a lot of the boutique gear are the paint jobs and roadworthiness/construction. Electronically speaking, there's a lot of slop out there. Not speaking of the OCD or Fuller's work per se, as I haven't seen it and have very little interest in it anyway.
Oh, and the protection-diode clipping thing was done by Aron around 8 yrs ago with his Shaka 3.
All right, but the VL oD has no tone control?
What kind of tone control is used on this one,
Proco Rat or TS style? other....
Perf layout for a Voodo Labs Overdrive with mosfet clippers coming :icon_mrgreen:
IIRC there was a thread a month or so back which discussed the clipping diodes NOT going to ground, but to 1/2v. and the effect this had on the clipping, perhaps being "softer". :icon_cool:
If the diode in the mosfet is being used rather than the mosfet, that seems somewhat misleading.
Quote from: WGTP on January 08, 2007, 12:02:08 PM
IIRC there was a thread a month or so back which discussed the clipping diodes NOT going to ground, but to 1/2v. and the effect this had on the clipping, perhaps being "softer". :icon_cool:
That will depend on how well the Vr rail is filtered. I found with my tonesource (another thread) that with Vr purposely underfltered (4.7u as in the brownsource schems) and critical parts of the circuit grounded to that, it will soften up the highs in a nice way. Whereas the more typical 22u or 47u filter cap (which I'm usually inclined to use) sounded a lot harsher.
Hmmm
In the DOD OD250 ('77 version) there is no cap in the Vr.
Can someone explain the role the cap plays in the Voltage Reference?
Thanks
John
Quote from: Basicaudio on January 08, 2007, 01:44:16 PM
Hmmm
In the DOD OD250 ('77 version) there is no cap in the Vr.
Can someone explain the role the cap plays in the Voltage Reference?
Thanks
John
It provides voltage stability and a "solid" AC ground.
The tone control is a guitar style one. O-cap is a tantalum, cera cap for the 1n, rest is multilayer ceramic, maybe tantalum for the 100n in the RC network. I think Sila Mica or PIO caps where much better in terms of tone and headroom but 4 of them and the board is full.
IMHO the part and build quality on Fulltone's FXs is boutique-standard. I like that Fuller don't mount the footswitches to the board like some other B-makers do (it took a hell of time to change a crappy switch in those FX).
Connecting the diodes/mosfets to VREF will give better headroom with less compression, a different breakup and a bit topend sizzle in the VL OD and OCD. To say this is better than connecting to ground or putting them in the FB-loop is a bit unfair, the rest of the circuit is important too and connecting diodes to VREF will not work in every OD/Dist. equal good as in the VL OD.
The design of bias devider has a lot effect on the tone, a 2x10k with a 10uF sound less trebly with a sloppy bass. Increasing the 10uF to 47 or 100uF produce better highs and a tighter bass. Sometimes I increase the 10k and parallel decrease the cap value.
A additional 10-100n from + to gound increase the treble response a bit too, but also filter out the hiss implied by the protection diode (that's the reason while the small cap is there).
Adding another 100uF from + to ground will make the FX even more trebly. To decide to take a 10uF or 47/100uF in Vref is sometimes not easy and often depends on the type of IC and the slewrate. Often I decide after a listening test to increase/decrease the caps in Vref to tailor the tone to my liking. IMHO the best way for most FX is to use a IC in the bias-devider to stabilize the circuit against load down influences and to generate a rel. sym. Voltage on the IC-rails.
The Xotic stuff f. ex. use a 10uF cap in the bias divider to soften the tone of the hifi-sounding IC.
JHS
Quote from: Doug_H on January 08, 2007, 01:30:39 PM
Quote from: WGTP on January 08, 2007, 12:02:08 PM
IIRC there was a thread a month or so back which discussed the clipping diodes NOT going to ground, but to 1/2v. and the effect this had on the clipping, perhaps being "softer". :icon_cool:
That will depend on how well the Vr rail is filtered. I found with my tonesource (another thread) that with Vr purposely underfltered (4.7u as in the brownsource schems) and critical parts of the circuit grounded to that, it will soften up the highs in a nice way. Whereas the more typical 22u or 47u filter cap (which I'm usually inclined to use) sounded a lot harsher.
I'm not sure if you could get by underfiltering the reference on the VLOD, as you might couple some of the output of the first stage(through the clipping diodes) to its input, as it uses the same reference. But if you add another Vr for the clippers, you could do anything you want with them. BTW, not that this means anything at all, but if you add a second Vr divider and cap to the VLOD, the parts count starts getting suspiciously close to what you see in the OCD pics.
I just added a second Vr string to my VLOD build and stuck the clipping circuit on my breadboard, hope to try out some clipping stage experimentation tonight. I also confirmed what JHS said about the diodes not having much of an effect (at least on a scope), if the level at the clippers start getting much over 0.7V or so, the second op amp stage starts to clip.
Another interesting point is that with the gain pot in the inverting leg to ground of the first stage as in the original VLOD, you have the 470K Rfb and a 220pF across it. That gives quite a rolloff. If you set the inverting leg to ground at 4.7K and then add the gain pot as Rfb (as indicated in the OCD mods on the Fullertone website), that would raise the rolloff frequency quite a bit at low gain settings. I'm going to try this as well to see if this helps add clarity to the VLOD.
Quote from: Basicaudio on January 08, 2007, 01:44:16 PM
Can someone explain the role the cap plays in the Voltage Reference?
Another way to think of it is as being like an emergency battery or reservoir of current such that there is always enough to accomplish the biasing should another part of the circuit create sudden demands on the battery.
The battery has a role akin to the wall current. In the "good old days", when there might not be all that many electrical appliances plugged into the wall, many of them lacked either power regulation/filtering or any attention to current-consumption. So, when your mother or grandmother or the tenant down the hall in your 3-storey walkup decided to use their Singer sewing machine, every sudden momentary surge in current consumption from the motor on that beast would translate in power line noise and static showing up on your radio or TV. If the compressor pump on the fridge came on during the critical play of the World Series, you might have to miss a few pitches. With everything sharing the same power, whenever one thing plugged into the same AC line needed lotsa current in a hurry, it would create an impact on the current available to other things plugged into the same line.
The cap between Vref and ground serves the same role as a well-regulated supply now does for all those appliances in your house: it helps them get through any momentary alterations in the available current supply by smoothing and storing current from the power source.
Now, of course, if you happened to be the ONLY appliance on a desert island, then nothing ought to interfere with your access to current, right? Right. When we have something like a modulation pedal where the LFO has current needs that are sometimes incompatible with the audio path current needs, Vref needs to be extremely well-smoothed and stabilized so that the two portions of the circuit don't fight each other and yield ticking. In the case of the DOD250, though, the circuit is only one lowly op-amp, so in a sense nothing is fighting anything else for mastery over the current.....I think. There may well be some conflicts between what the V+ pin needs on a moment to moment basis and what the Vref pin needs, so while the 250 circuit likely could function without that cap, perhaps it performs a little better with it under certain circumstances.
OMG
one of the oldest rules in EE:
"a circuit is only as good as its power supply"
the output cap is a 2,2uF electrolytic,
the 220pF caps seem to be standart ceramics and everything else seems to be multilayer ceramic.
wouldn`t a tantalum output cap bring more transparancy to the exit?
jep,
more transperency and a bit more raunch,
the whole pedal will sound even warmer and more transparent
if you would use some nice film caps and silva mica's for the 220pf.
I think the two 220pF caps would make the most differnce.
ahh: I fought so!
Anyone want to help me trace this sucker?? I have one here on loan, and I got lots o' pics i've taken. I'm not much on tracing double sided boards, but I can provide pics/info to someone willing to give it a go.
>The type of mosfet has nearly zero influence on the sound, only the internal protection diode is used for clipping.
Hmmmm wonder where he got that from?
Yeah, that's what I thought also Aron.
Quote from: aron on March 15, 2007, 03:11:05 PM
>The type of mosfet has nearly zero influence on the sound, only the internal protection diode is used for clipping.
Hmmmm wonder where he got that from?
Actually I have to admit :icon_redface: I sent him a drawing and info on using MOSFETs as diodes before Aron did his pedal. I don't even remember why we were emailing back and forth at the time, it was before I built the GlassPak and was experimenting with using MOSFET diodes on a tubescreamer circuit. He said I should be careful about just 'giving' ideas away like that because I could actually profit it from it if I played it right. I didn't really care much about it then though. If he used this info for the OCD, I have no idea, but he did have 'prior knowledge'.
--john
>Actually I have to admit icon_redface I sent him a drawing and info on using MOSFETs as diodes before Aron did his pedal.
But John, you used you didn't use the _internal_ diodes. That's the big difference between your MOSFET use and mine.
Quote from: aron on March 16, 2007, 03:50:24 AM
>Actually I have to admit icon_redface I sent him a drawing and info on using MOSFETs as diodes before Aron did his pedal.
But John, you used you didn't use the _internal_ diodes. That's the big difference between your MOSFET use and mine.
I didn't use the internal diodes in my pedal, doesn't mean I didn't try it, experiment with it, etc. Also, you didn't -know- you were using the body diode until after a rather lengthy discussion on the forum (was it ampage?). :icon_wink:
There were more people than you that tried this, but in the MOSFET diode connection, it is really sensitive to the MOSFET you use and each and every person assumed they had the extra diode in wrong and flipped it over (so it uses the body diode) and decided that was 'better' because it was a more pronounced, harder distortion. My point being, several people followed the same path as you pretty much independently, they just didn't post any schematics.
Slightly off topic, I just dug through my junk box last weekend and dug out a tubescreamer board I did Jan 1, 1998 that uses the body diode of MOSFETs for clippers. In the feedback loop AND to ground after. I also have one that uses JFETs wired as diodes. I also found several amp simulators I did with JFETS from 95 and 96. I have a Fender version, 2 Marshall 18 watt (EL84) versions, one that even uses an output transformer (it took a lot of work to get the biasing right and still have gain) and one that doesn't. But I have a feeling that if I came out with a pedal that uses any of this decade old development I did, I would be accused of 'stealing' from schematics published here just in the past year. I find this growing trend of "I published it first, therefore I own it" attitude rather disturbing.
--john
Do we know for sure which way the OCD is using the mosfets?
John has been very helpful lately with explaining the various ways to use mosfets, and I for one greatly appreciate it.