Dunlop - Octavio

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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gena_p1
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Post by gena_p1 »

sinner wrote:
Alex Frias wrote:No, I think our friend RnFR is just a bit confused by so many Octavias, as Dunlop promotes ...

does the values are correct? R3 looks more like 1k8 to me...
R6 (between 22u and 5K1) is not 22K, it's 220K.

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gena_p1
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Post by gena_p1 »

And fuzz pot is alpha 24mm B5K.

Just finished repairing of one unit. Stupid device, came from another town, from another soldier. I though, it's piece of cake, - 3 transistors, 2 diodes, but I was wrong too much :)

With two multimeters, tone generator and oscilloscope i spent 5 hours in measuring and replacing components, cause signal does not flow even through 1st transistor (BC549b/mpsa18).
I tested 80% of details, all was working, power OK, wires working too. B,C,E voltage of bc549 was strange - 0-0.8V, 2.6V, 0-0.1V.
At last I began to shortcut everything, and after shortcut of R8 (47K), device resurrected!

What it was? Charged electrolytic capacitor locked down trannies, and formed deadlock?
I want to understand, cause device was not working in several days, and contained no battery inside, but magic axials didn't discharged.

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kymar
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Post by kymar »

And fuzz pot is alpha 24mm B5K.
And level pot is alpha 24 mm A500K with switch :D

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Ghandi
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Post by Ghandi »

hi there,
anybody tried that pedal with the TM011 transformer with the 1:3 ratio?

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Ghandi
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Post by Ghandi »

oh and are the last changes...
18k, 220k and 5k & 500K pot values verified?

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kymar
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Post by kymar »

Ghandi wrote:8k, 220k and 5k & 500K pot values verified?
fuzz pot is B5K, volume A500k
R6 is 220k and there is no 18k resistor
Ghandi wrote:hi there,
anybody tried that pedal with the TM011 transformer with the 1:3 ratio?
I change Q3 from BC549 to MPSA18
C8 from 4700pF to 1000pF
C5 from 22mF to 47 mF
Fuzz pot from B5k to B1k
R6 from 220k to 22k
remove C4 and R5
I found it sound more versatile

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Alex Frias
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Post by Alex Frias »

Is there anybody out there with another original unit who confirm the values seen here? I've changed the R6 to 220K and got a worse result in sound and performance...

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marjodp
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Post by marjodp »

Can anyone tell me original dimensions (W x H) of a original pcb?

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Liquitone
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Post by Liquitone »

Ghandi wrote:hi there,
anybody tried that pedal with the TM011 transformer with the 1:3 ratio?
Yes, i build mine with a TM011, but with a 47uf instead of 33uf cause I didn't have them at the time.
I used BC 109C for Q1. I never tried a real one but I think it sounds pretty ok.

Here are two songs I used it on during the leads,
sandwiched between a germanium booster and a plexi-drive, guitars tone and volume dialed down;
http://soundcloud.com/liquitone/love-re ... head-oct25
http://soundcloud.com/retrospective-2/she-wants-me

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andregarcia57
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Post by andregarcia57 »

ok

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Post by Axeman.Bodie »

Hello fellow pedal enthusiasts,

I'm attempting to copy the parts of the Dunlop Octavio exactly in attempt to rehouse the copy in
a smaller more pedal friendly case, as well as allow it to be powered by 9v DC. Most of these parts are standard,
except the transformer, a 3.6 : 1+1 I believe to be created by MCE Magnetics. I can't seem to be able to purchase this
exact part anywhere and no pedal sites seem to even sell transformers like that.
Any ideas?

Also any tips on switching a positively grounded pedal to be powered by a 9v supply would be greatly appreciated!
The Transformer
The Transformer
The Board
The Board

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alexradium
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Post by alexradium »

i did a Madbean project for the standard adapter,i guess it was the Retrograde,something like that
otherwise you have to use a Roadrage project with a max1044 to get a negative voltage.
As a tranny you could use something like this
http://uk-electronic.de/onlineshop/prod ... 5a36a6a90e

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Bside2234
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Post by Bside2234 »

Alex Frias wrote:I think it looks like a better aproximation:

[ Image ]
A friend of mine wants me to build him one of these so I traced it based on all the pictures I can find and then compared it to what you guys got. I pretty much came up with the same thing. There are a few things that
I would like to verify/clear up:
1. Referring to the posted schematic here: Q1 (which is actually Q3 on the circuit board) shows the emitter going to R9/1K and the collector going to the R4/220K, R11/220E junction. I think this is drawn backwards. The pictures/trace
show the collector to R9/1K and the 220K and 200E to the emitter. Here's the datasheet: https://www.onsemi.com/pub/Collateral/BC550-D.pdf
2. Do we know that actual diodes for D1 and D2?
3. Is there a ground plane on the PCB? I can't see any traces for point TP1. I think this should be connected to Battery + via a ground plane maybe. Curious as the rest of this supply seem to have traces.
4. The diodes are connected to the what side of the transformer? Primary or secondary?
5. The actual pot values. I read they were measured in circuit as 12K and 126K but then there are posts where they say they are 5K-B and 500K-A.

I'm working on doing a full trace and proper schematic for this but need these points clarified then I'll post what I have.

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lespaulnmarshall
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Post by lespaulnmarshall »

Hoping not to really hijack the thread, but I recently got a Dunlop octavio. My Fulltone Octafuzz is quite a bit louder. I was just wondering if that is normal and if there is any technical explanation behind that? Thanks, Maurice

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lespaulnmarshall
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Post by lespaulnmarshall »

lespaulnmarshall wrote:Hoping not to really hijack the thread, but I recently got a Dunlop octavio. My Fulltone Octafuzz is quite a bit louder. I was just wondering if that is normal and if there is any technical explanation behind that? Thanks, Maurice
I should add that I always run the pedal with the boost/fuzz all the way down and the volume turned up. With the volume maxed on the octavio it's probably around the same level as the fulltone at 2 o clock.

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floobydust
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Post by floobydust »

It has less gain and more treble than the Tycobrahe, due to the 22uf capacitor to transformer rather than the 33uf.

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