Dunlop - Octavio

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

Very nice work, congratulations Alex!
Can you draw all the mods that you made on a schematic of Tycobrahe?

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dai h.
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Post by dai h. »

can someone explain the difference (around the gain pot) with the commonly circulated version? Is it just basically a way of getting more control (if a linear taper is used, I suppose that is a easier/cheaper way of getting more control of the octave/fuzz threshold rather than Mark H.'s idea of using a rev. audio taper--not that that is a bad idea)?

re: the sound clip, if someone told me (the first portion) had the same sort of circuit Hendrix used, I would be inclined to believe it. Reminds me of the sound clips of the Chicago Iron IIRC.

Thanks for posting the experimentation and sound clip Alex!

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Alex Frias
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Post by Alex Frias »

Well, I'm a very interested in "octavers" and this one really impressed me, but it's a real pleasure to know our efforts could be of any help for others.
Thanks for everyone who is invoved in those so interesting threads.

In relation to the "boost/gain engine" I must add that was one the best I achieve in terms of performance. But as I used a linear 10K pot, it' may be better yeat.

Anybody could offer this info about the pots used on this box?

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RnFR
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Post by RnFR »

regarding the pots- i'll try and give it a check tonight. sorry it's takin so long! :blackeye
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Alex Frias
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Post by Alex Frias »

Don't worry! You are always a great helpfull person! :applause:

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drewl
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Post by drewl »

I have one of these that the owner wants a dc jack installed.
Obviously with positive ground it needs a seperate supply.
For you guys that added the dc jack, how are you powering it?
Standard "Boss" type adapter?
I was impressed, it sounds pretty good. The octave seems to be more present on a wider range of notes than any of the Tychobrae clones I've built.
I'll have to compare them side by side.

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azrael
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Post by azrael »

^Standard boss. Just look at the wiring on generalguitargadgets for a PNP pedal.

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Alex Frias
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Post by Alex Frias »

I've compared them and the Dunlop supposed clone exceeds it in many aspects, in my opinion...
The exact nature of the transformer remains unknown. Our friend RnFR soon will reveal us the exact pot values.
However I'm very happy with the results as it is now.

Regarding the DC jack. I've used the same wiring as regular pedals like BOSS, etc. Obviously taking care the fact it's inverted polarity and using a separate power supply sharing it only with other positive ground projects I use in my pedalboard, like Fuzz Face clones. A couple of protecting components may be added, as the Dunlop itself has no one as it's intended for battery use only. A cap and a diode may do the job.

I still need to do a very large power supply to feed all my projects in use. Some even use 12 volts (my Electric Mistress clone) and symetric +9/-9 (my CA Ring Modulator, Maestro S&H filter). Something like a voltage doubler using MAX1044 may be a solution too.

I plan to install a 3 way toggle switch (DP3T -> ON-OFF-ON type) to give it three possible effects in a very inexpensive way:

1 - A "body mod", wich makes it more synthy and not so "wild". It adds a couple of high frequency rolloff caps-to-ground at the input (.047uF) and the trafo secondary/input (.1uF) point, after the 22uF cap.
2 - Nothing, just to use it as it is
3 - A LED from the output diodes to ground, it enhances a bit the crappy "sitarish" sound found on Tim Escobedo's Psychtar and Jawari projects.

As I don't love the distortion created without the octave effect in this project, I have no plans to put a switch to cancel one of the diodes output, as seen in some units of this type. But it's a valid option to others.

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drewl
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Post by drewl »

Want me to measure anything while I have this apart?

As far as my Tychobrae clone, the one was a kit from GGG I think, I put the switch in to cancel the octave and subbed in different transistors until I got it to sound like a good fuzz when not in octave mode.

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Alex Frias
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Post by Alex Frias »

It's really a matter of taste, I prefer to use other gadgets, like Fuzz Factory, to get the nastiest fuzz sounds and leaving the Octavio for what it does better, in my opinion. So I decided not to add that possibility.

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Post by soulsonic »

Alex, you should experiment with smaller coupling cap values going to the primary of the trafo. When I was experimenting with the Octavia circuit on breadboard, I found that smaller values there does much to clean up the splatty low-end and get a clearer octave.
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Alex Frias
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Post by Alex Frias »

Thanks for the tip! I tried some smaller values in my Tyco clone and like it in some way, confirming what you said about it. But definitely I like that mex of the octave up effect added but retaining the bassier body of the tone this kind of circuit gives. At the lower part of the scale you almost get an octave down effect. But who knows another toggle to swap caps at the input of the trafo... just to do some specific aplitations...

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drewl
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Post by drewl »

While testing this out I noticed DC voltage on the output, because it has no output coupling cap.
According to an earlier post this is normal for this unit.
Anyone else find that odd?
No unwanted effects?

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gigelmargel
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Post by gigelmargel »

I've just modified my Tycobrahe Octavia to Dunlop Octavio and it's far away better (more useable pots).
It has only two little problems:

1. I used for gain pot a 10k linear one and it has a dramatically action in the last 10-15%...I will try to use a 4.7k or 2.2k logarithmic backward wired
2. The volume pot (500K) increase very much at the end...why?

Thx a lot all of you for your fantastic work!

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floobydust
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Post by floobydust »

I am going to make one, but I'll try some different types of vintage Mullard-Philips .1uf caps for the input cap. A lot of mine are still good. :hmmm:

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Alex Frias
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Post by Alex Frias »

I'm still using 10k lin for the boost/gain and 500k log for the volume. Possibly 5k or 4k7 may be better for the gain/boost, anyway I am ok with those for basic setting...
I will wait for the info about the Dunlop pots, at now it's very useable and can't leave my main pedalboard.

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gigelmargel
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Post by gigelmargel »

Alex Frias wrote:I will wait for the info about the Dunlop pots, at now it's very useable and can't leave my main pedalboard.
Me too :)

I hope we will get the values of the pots soon :)

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floobydust
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Post by floobydust »

gigelmargel wrote:
Alex Frias wrote:I will wait for the info about the Dunlop pots, at now it's very useable and can't leave my main pedalboard.
Me too :)

I hope we will get the values of the pots soon :)
Theres one at a local GC. I think I'll just pick it up tomorrow and post the pot values here.

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Alex Frias
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Post by Alex Frias »

BRAVO!!! :applause:

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gigelmargel
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Post by gigelmargel »

I beg someone who have an Octavio to open it and to tell me the value of the pots.
Anyway, I replaced the 10k gain pot with 4.7k and 1k and it seems to me that 4.7k sounds better.

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