Fulltone - OCD  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
jymaze
Resistor Ronker
Posts: 374
Joined: 06 Mar 2011, 23:19
Has thanked: 86 times
Been thanked: 167 times

Post by jymaze »

On first intention, just put a jumper instead of the 18k resistor in the first opamp feedback loop (the one in series with the 1Meg pot). The minimum gain will then be merely a slight boost.

geiristudio
Breadboard Brother
Posts: 127
Joined: 02 Jun 2011, 16:40
Has thanked: 3 times
Been thanked: 21 times

Post by geiristudio »

jymaze wrote:On first intention, just put a jumper instead of the 18k resistor in the first opamp feedback loop (the one in series with the 1Meg pot). The minimum gain will then be merely a slight boost.
Alright, I'm gonna try that, thanks!

User avatar
ebuprofen
Breadboard Brother
Posts: 133
Joined: 03 Nov 2009, 07:51
Completed builds

http://ebupro.blogspot.com/

Location: Estonia
Has thanked: 12 times
Been thanked: 12 times

Post by ebuprofen »

hey guys, what would be a good value for pot instead of 22k resistor in HP mode? so I could adjust the amount of boost? 500kB?

yongki
Posts: 40
Joined: 13 Aug 2008, 21:20

Post by yongki »

Image

Branimir
Posts: 38
Joined: 20 May 2009, 15:25
Completed builds

Fuzz Face, Small Stone, Trem Lune, Fet Muff, Big Muff (green), Fuxx Face, Son of Screamer, Rat, Rebote 2.5, Opamp Big Muff, EA Tremolo, Easyvibe, Axis Face Si, Ross Compressor, Ross Distortion, DLS

Location: Zagreb, Croatia
Has thanked: 1 time
Been thanked: 2 times
Contact:

Post by Branimir »

Trying to find info...

What type of capacitors are use in OCD V4?
Electrolytics are tantalum? All of them? What about the others?
If you scoop, it sounds like poop!

batteryacidtea
Breadboard Brother
Posts: 109
Joined: 18 Feb 2009, 04:42
Has thanked: 57 times
Been thanked: 16 times

Post by batteryacidtea »

Theres just one capacitor (one of the 10uF's) is Tantalum, the others are eletrolytics. The tantalum cap is usualy highlighted in the schematics, I don't remember wich one it is, but is easy to find out

jymaze
Resistor Ronker
Posts: 374
Joined: 06 Mar 2011, 23:19
Has thanked: 86 times
Been thanked: 167 times

Post by jymaze »

Just a correction to the statement above:

Quote: "There's just one capacitor (one of the 10uF's) is Tantalum, the others are film capacitors."

The big polar capacitors of 10uF or more are electrolytics, except C7 that is tantalum (electrolytic here would be just as good).

Actually tantalum capacitors are the worst thing for signal (huge hysteresis) so even an electrolytic for C7 is better in that respect.

Branimir
Posts: 38
Joined: 20 May 2009, 15:25
Completed builds

Fuzz Face, Small Stone, Trem Lune, Fet Muff, Big Muff (green), Fuxx Face, Son of Screamer, Rat, Rebote 2.5, Opamp Big Muff, EA Tremolo, Easyvibe, Axis Face Si, Ross Compressor, Ross Distortion, DLS

Location: Zagreb, Croatia
Has thanked: 1 time
Been thanked: 2 times
Contact:

Post by Branimir »

Hm, I've never actually payed attention to capacitors, I used polypropylene capacitors, does film capacitor means polyester capacitor in this case, and does it really matter? 8)
If you scoop, it sounds like poop!

jymaze
Resistor Ronker
Posts: 374
Joined: 06 Mar 2011, 23:19
Has thanked: 86 times
Been thanked: 167 times

Post by jymaze »

Polyester are the cheapest of films caps so that is what is used usually (versus polypropylene, polycarbonate or polystyrene). It does not matter that much anyway for guitar application, just take the cheapest. At least, I would avoid tantalum for sure.

batteryacidtea
Breadboard Brother
Posts: 109
Joined: 18 Feb 2009, 04:42
Has thanked: 57 times
Been thanked: 16 times

Post by batteryacidtea »

jymaze wrote:Just a correction to the statement above:

Quote: "There's just one capacitor (one of the 10uF's) is Tantalum, the others are film capacitors."

The big polar capacitors of 10uF or more are electrolytics, except C7 that is tantalum (electrolytic here would be just as good).

Actually tantalum capacitors are the worst thing for signal (huge hysteresis) so even an electrolytic for C7 is better in that respect.
I was refering to the polarized ones, now I see I didn't answered the question properly. The pF values are ceramic, the nF values are greenies and the polarized caps are eletrolytic, just C7 (as jymaze stated above) is tantalum

Branimir
Posts: 38
Joined: 20 May 2009, 15:25
Completed builds

Fuzz Face, Small Stone, Trem Lune, Fet Muff, Big Muff (green), Fuxx Face, Son of Screamer, Rat, Rebote 2.5, Opamp Big Muff, EA Tremolo, Easyvibe, Axis Face Si, Ross Compressor, Ross Distortion, DLS

Location: Zagreb, Croatia
Has thanked: 1 time
Been thanked: 2 times
Contact:

Post by Branimir »

I never really payed attention to the caps, I just bought the ones that are available, okay so it's not critical to use that tantalum after all... Though I'm stupid, I have tried the V4 original and built mine and frankly, they sound the same, I just don't have them next to each other to A/B them properly.
If you scoop, it sounds like poop!

User avatar
Intripped
Cap Cooler
Posts: 553
Joined: 25 Aug 2009, 02:03
Location: Italy
Has thanked: 687 times
Been thanked: 215 times

Post by Intripped »

Just wanted to put some light on how exactly the clipping transistors and the germ. diode are connected.
I have a V4 here on my bench and I see that Source and Gate are connected together (trannies are 2n7000).
So we have S+G and D, where D corresponds to the striped end of a normal diode.

---->|---[S+G] [D]----
This represents how the germ diode and the 2n7000 are connected in series

howmuch
Posts: 35
Joined: 09 Nov 2014, 19:31
Has thanked: 8 times
Been thanked: 22 times

Post by howmuch »

Intripped wrote:Just wanted to put some light on how exactly the clipping transistors and the germ. diode are connected.
I have a V4 here on my bench and I see that Source and Gate are connected together (trannies are 2n7000).
So we have S+G and D, where D corresponds to the striped end of a normal diode.

---->|---[S+G] [D]----
This represents how the germ diode and the 2n7000 are connected in series
Thanks for posting some first hand evidence on the connections.
It still seems to be widely (and wrongly IMHO) accepted that the gate is connected to the drain (as in the schematic yongki posted above), even though people have hinted otherwise earlier in this thread.
So does your OCD have the same clipping configuration as the Joyo clone's corrected circuit I posted here - the "Circuit when D2 is in the "correct" orientation"?
Image

You've got ---->|---[S+G] [D]---- and the corrected Joyo is electrically the same with ----[S+G] [D]---->|---
Or put another way, on the schematic yongki posted above, move the gate connections from the drains to the sources?

User avatar
Intripped
Cap Cooler
Posts: 553
Joined: 25 Aug 2009, 02:03
Location: Italy
Has thanked: 687 times
Been thanked: 215 times

Post by Intripped »

howmuch wrote: So does your OCD have the same clipping configuration as the Joyo clone's corrected circuit I posted here - the "Circuit when D2 is in the "correct" orientation"?
[ Image ]

You've got ---->|---[S+G] [D]---- and the corrected Joyo is electrically the same with ----[S+G] [D]---->|---
Or put another way, on the schematic yongki posted above, move the gate connections from the drains to the sources?

YES to all

...and to avoid any further confusion, here is the exact clipping section:
Attachments
Untitled-2 copy.png

SamBloody
Posts: 2
Joined: 24 Jul 2016, 19:28

Post by SamBloody »

Hi guys!
Can you give me verified fulltone ocd pcb layout?
Thanks!

User avatar
storyboardist
Breadboard Brother
Posts: 96
Joined: 28 Dec 2013, 01:08
Location: Georgia, USA
Has thanked: 74 times
Been thanked: 197 times
Contact:

Post by storyboardist »

Here's my layout.

Image

287m
Breadboard Brother
Posts: 115
Joined: 11 Nov 2014, 23:51
Location: Heaven ~ Hell
Has thanked: 346 times
Been thanked: 61 times

Post by 287m »

Nice layout David :thumbsup
perfect for 1590B

so i present to 1590A Club masochist :mrgreen:
Image
reff sch https://4.bp.blogspot.com/-G_jLNr0ZECI/ ... cd-sch.png

SamBloody
Posts: 2
Joined: 24 Jul 2016, 19:28

Post by SamBloody »

Thank you,guys!

V1nce69
Posts: 36
Joined: 10 Nov 2013, 09:01
my favorite amplifier: Ampeg
Completed builds

Veroboards builds:
Throbak Overdrive Boost
Wampler Ecstasy
Creepy Fingers Doomidrive
Black Arts Quantum Mystic
Roger Mayer Voodoo Bass
Idiot box Blowerbox

Pcb builds:
Fulltone 69 (GGG kit)
Russian Big Muff (Musikding kit)
EHX Bassballs (home etched using Topopiccione layout)
BJFE BBOD (home etched, thx FSB)
Triangle Muff (Guitar PCB board)
Deluxe Bass Fuzz (home etched,gausmarkov.net layout)

Location: Lausanne, Switzerland
Has thanked: 34 times
Been thanked: 65 times

Post by V1nce69 »

Hi all,

I own an OCD #84590 with a pcb revision 1.4. Wanting to know how it works, I traced the complete pcb and made a drawing out of it. Here are a few pics and my drawing.

It might be of some interest.
OCD gutshot
OCD gutshot
OCD pcb top view
OCD pcb top view
OCD pcb bottom view
OCD pcb bottom view
OCD pcb bottom view - detail
OCD pcb bottom view - detail
OCD pcb 1.4 layout
OCD pcb 1.4 layout

User avatar
Intripped
Cap Cooler
Posts: 553
Joined: 25 Aug 2009, 02:03
Location: Italy
Has thanked: 687 times
Been thanked: 215 times

Post by Intripped »

nice work!
just a little note:
in your drawing, 2N7000 pins are named wrong

Post Reply