Fulltone - OCD  [traced]

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Goop_buster
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Post by Goop_buster »

Thanks JHS :D

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Post by freedreamer »

i guess markm's version is not like this....

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Post by briggs »

https://www.aronnelson.com/gallery/v/Mar ... 5/album76/

It looks like it to me.


--------


admin edit 11/09/07
Fulltone OCD parts layout
Fulltone OCD pcb transfer file

schematic further on in the thread
the above old link is dead.
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Post by cbriere »

there are error on the posted circuit from JHS
please indicate schematics of the OCD++ layout

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Post by JHS »

The OCD++ is "my personal version" of the OCD wiith some minor mods and refinaments added, nothing more. I prototyped all 3 versions of the original and this circuits suits me best.

If you intend to build one of the original circuits I recommend to take Mark's layout and build his OhCeeDee. Only drawback, it has not the original LED-control circuit and you'll get a pop if you use a LED indicator and true bypass wiring, the original OCDs have no tone-sucking pulldown R.

If someone claims there are any errors in it please correct the schem and repost it ...

JHS

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Post by kagaxdx »

The OCD++ is "my personal version" of the OCD wiith some minor mods and refinaments added, nothing more. I prototyped all 3 versions of the original and this circuits suits me best.
:roll: So... where's the true OCD schem?
Why we can't have a look at it?

Thanks anyway for showing us your version for the OCD...

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Post by JHS »

The org. schems are for my eyes only and I don't have the permission to post it.

If you want an org. schem (w/o the LED circuit) generate it from Mark's layout, you need max. 5 minutes for it. Fulller already posted the basic differences of the 3 versions. I think it's not to difficult to change 1/2 pot values and a cap value in the schem to generate schems for all 3 versions.

98% of my schem is nearly identical and if you use ML_ceramics and tantal electrolytics the circuit shown in my schem delivers the OCD sound. Even with SM/Styro and MKT caps it comes close and the sound wil be a bit warmer.

JHS

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Post by markm »

JHS wrote:The org. schems are for my eyes only and I don't have the permission to post it.
Is the OCD another "trade schem" like the KLON was? :?:
How can I get involved in schem trading like this?
Seriously!
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Post by cbriere »

can you comfirm how the Switch is wired? (on the markm layout)

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Post by JHS »

I have 3 schems of the OCD (V1,V2,V3), the guys who traced them own the units and they are verified. I promised not to distribute the schems, hence that's the reason I don't publish them.

33k and 22k is correct, 33k is the HP-mode and 33k with 22k parallel you'll have the LP-mode. You can connect the empty pole of the switch to the junction of the 33k/22k like it's done in the OCD, but this has no effect on the sound.

The LP mode sounds really good, the HP-mode sounds to peaky and thin for me, I think I will mod the HP-mode on my clone and therefore swap 2 new Rs in.

JHS

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Post by markm »

JHS wrote:I have 3 schems of the OCD (V1,V2,V3), the guys who traced them own the units and they are verified. I promised not to distribute the schems, hence that's the reason I don't publish them.
What if you re-draw them?

The LP mode sounds really good, the HP-mode sounds to peaky and thin for me, I think I will mod the HP-mode on my clone and therefore swap 2 new Rs in.
I agree.
Very Peaky!
My Layout is the OCD, what version......I don't know.
It is renamed to protect the innocent and to fit forum rules.
Other than that, it is what it is! :lol:
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Post by snoof »

according to the link to Fuller's site posted earlier, it's V1. Pots are 500k, 25k, and 100k.

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Post by briggs »

Mosfet clippers. I've really got to get myself some 2N7000 thingys
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Post by cbriere »

i'll just put some Mosfet clipper to replace the diodes on my BOSS DS-1 , saves me alot of time not have to build the whole thing.
BS170 should be OK?

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Post by analogguru »

i'll just put some Mosfet clipper to replace the diodes on my BOSS DS-1 , saves me alot of time not have to build the whole thing.
BS170 should be OK?
Save your time, when you want to do it like fuller did.....
That´s not mos-fet-clipping, that´s normal diode clipping even with mosfets
The inside-protection diodes are not mosfet-diodes, they are normal and will conduct long before the mosfets will conduct.

Have a look here:
https://www.diystompboxes.com/pedals/schematics.html

(scroll down for Shakah braddah III) to see how it should be done.

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Post by modman »

wow, we went round in a circle, I remembered some old post on the OCD and dumped at the beginning of this thread. Please reread the thread on the mosfet stuff.
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Post by MKB »

FWIW, I built a VLOD recently, and it sounded flat and poor. I then made the OCD modifications in the link JHS posted to the VLOD, and also the mods on the Fulltone site, and the difference was fantastic. I haven't played a real OCD, but the modded VLOD is so good I don't really want to. I used BS170's in place of the 2N7000's though. The real secrets perhaps are the fet clipping, capacitor types and the op amp (TL082). They make a HUGE difference. The dynamics are indeed there. With the guitar volume down it sounds almost identical to when it is bypassed, but crank the guitar volume up and it very nicely starts distorting.

Another secret is to keep the gain below 12 o'clock. The modded pedal sounds fuzzy and bad if the gain goes above that. If you want high gain, boost the pedal with a clean boost, it sounds great that way.

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Post by bajaman »

Hi MKB - thanks for your comments
How much difference is there between using a TL072 or TL082 :?:
i always understood them to be the same - just that the 072 was a lower noise version - am I wrong here :?: Anyone know :?: comments etc most welcome :wink:
bajaman

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Post by MKB »

bajaman wrote:Hi MKB - thanks for your comments
How much difference is there between using a TL072 or TL082 :?:
i always understood them to be the same - just that the 072 was a lower noise version - am I wrong here :?: Anyone know :?: comments etc most welcome :wink:
bajaman
I tried recent production versions of the TI TL072 and TL082 in the circuit, the TL082 definately improved the transparency of the sound, which is the main benefit of the circuit IMO.

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