Octave Up

[fuzzo]

Hi guys,

Maybe I'll make an octave up pedal (without fuzz) with different controls . But which one can give the best sound ? 

AOP : http://www.lynx.bc.ca/~jc/superFullWave.html

or old design with Biploar transistor as we can find in Roger mayer Octavia ou Gring ringer ? the famous transistor with diodes on emetter and collector.

Also, and , I think the most important thing, I would like to incorporate a tone control that works like the guitar tone. When I kick my ultimate octave I like to turn down the tone to attenuate the highs and have some kind of smoother and agressiveless octave up sound. So,  How I can add a similar control ?

I thought add it before the gain stage, the guitar (and so, its tone control)  being before all effect. A simple low pass filter with correct values or something more complex  ?

[MikeH]

Clean octave up is pretty much impossible to make happen DIY.  They almost all have at least a little fuzz.  RM octavia is very much a fuzz.  Breen ringer, while cool, has a little more of a ring mod type sound than an octave pedal.

You won't find it here, but if you scour the web thoroughly you'll find a schematic for the zvex johnny octave, which is my favorite.  It's still a little fuzzy, but the octave is more prominent and doesn't get lost in the fuzz as much.

[fuzzo]

Clean octave up is pretty much impossible to make happen DIY

yeah I know. I don't want a pure clean octave like a whammy does (not so clean too) but a vintage octave up like the foxx tone machine or the green ringer. I remove the fuzz part to put with any ditortion or fuzz pedal I want . In my idea taht will be like that :

Gain stage (to pass to a "regular" octave up to a screaming octave up (like if you boost it))  Tone (to reduce highs and have a smoother sound) --- octave up part (Op amp or transistor ) --- volume knob .

I'll draw a schemo that can help to see what I'm taliking about.

[rousejeremy]

Prescription Electronics makes a pedal called the Clean Octave Blend.

I haven't been able to find any sound clips, but I did build one using a Torchy vero that didn't work.

i could post the vero and you could compare it to the schematic on another forum which can be found online to see if it's any good.

[Br4d13y]

the push me pull you by escobedo is one of the best, check that out, its quite clean

[fuzzo]

Prescription Electronics makes a pedal called the Clean Octave Blend.

I haven't been able to find any sound clips, but I did build one using a Torchy vero that didn't work.

the schemo :
http://analogguru.an.ohost.de/001/schematics/Prescription_COB.gif

I want to do something close but with a tone pot to alter the octave color, have a agressive octave up sound  or smoother octave (as when you play on the neck pickup in removing all highs, "little sister" by QOSTA).  With that, maybe, I'd add a boost before the octave part to boost it and have this kind of sick and freaky octave up (Thing I do with my fulltone ultimate and a boost before).

For the clean (or blend ) pot , I though about it but I don't know if that will be really usefull.

[rousejeremy]

Prescription Electronics makes a pedal called the Clean Octave Blend.

I haven't been able to find any sound clips, but I did build one using a Torchy vero that didn't work.

the schemo :
http://analogguru.an.ohost.de/001/schematics/Prescription_COB.gif

I want to do something close but with a tone pot to alter the octave color, have a agressive octave up sound  or smoother octave (as when you play on the neck pickup in removing all highs, "little sister" by QOSTA).  With that, maybe, I'd add a boost before the octave part to boost it and have this kind of sick and freaky octave up (Thing I do with my fulltone ultimate and a boost before).

For the clean (or blend ) pot , I though about it but I don't know if that will be really usefull.

Here's the vero, maybe someone with a good eye can compare it with the schematic?

Sorry if I'm stepping in on your thread a bit but I built it yesterday and can't get it working, when I connect the power, the whole thing grounds out. 

[fuzzo]

no problems, I saw your message on freestompboxes. This veroboard is really messiness.

So, I drew a shemo of what I would :



nothing really complex. But what does the 100K resistor connected to the diode's anode to the V+ ? I saw the same thing on this schema :

http://www.sonelec-musique.com/images2/electronique_transposeur_octave_up_002.gif

If I well understood, that serves to set the negative and positive part of the signal.

[fuzzo]

I'm still looking for a tone control to add in my project

Do you think the bend or mix control can be useful ?

[monkmiles]

Hi guys,

Maybe I'll make an octave up pedal (without fuzz) with different controls . But which one can give the best sound ? 

Did you end up getting anywhere with this project? I know what you're talking about and would be interested myself in one.

[fuzzo]

Hi,

I tried the JC maillet octave up schematic (the one using AOP) and I wasn't really happy with it. so i came back to the vintage and started a Green ringer with "gain" "tone" et volume control I'll add . (and the null mod )

[Mark Hammer]

One of the things that limits how "clean" octave-up devices can be is the crossover distortion introduced by the use of the series diodes needed to derive individual half-cycles.  In the COB schematic you linked to, yo can see D1 and D2 near the output.  Nothing will get past them unless it surpasses the forward voltage of the diodes in question.  That means that the sides of the waveform will be chopped, resulting in an alteration of the harmonic content of the signal, even after one "stitches" the two wave-halves together again.  That bottleneck occurs on virtually every octave-up unit I've seen that uses a phase-splitter.

Another bottleneck, addressed in part by JC's nulling mod, is that of matching the levels of the two half-cycles.  In order for us to perceive the frequency as having been doubled, the number of equal-amplitude peaks has to double.  If the number of peaks is doubled via rectification, but every second peak is slightly lower in amplitude, it tends not to get heard as doubling.

Finally, there is the extent to which the circuit gives preference to what is probably a fundamental, versus what is probably just a harmonic.  If I were to double all the harmonics in frequency, it would just sound fizzier, not an octave higher.  It is the network betwen Q1 and Q2, but more particularly the network between Q3 and Q4, that makes the octave so robust in the COB, and in the Foxx Tone Machine.

[fuzzo]

thanks for that explanation Mark !

But the fuzz distortion in foxx tone or Roger mayer octavio accentuate the octave up in compressing the sound, no ? 

[Mark Hammer]

The Foxx has a pair of clipping diodes after the octave-generating portion, so yes it compresses the sound.  I don't remember what the Mayer pedal has.

[fuzzo]

Actually , the Roger mayer has a similar design, espacially the kind of notch filter between both transistors.

Well, I started working on Green ringer PCB, I'll finish it and see what I can do . The first thing I'll do is to add a gain stage at output to increase the level and have a volume control. I decided to add the tilman jfet booster (J201) which looks good.

[cpm]

i've been messing with rectifier:
http://www.edn.com/article/CA6339250.html
very simple and effective

it will benefit from some input gain and lowpass filtering, also find some fizzing on inaccurate low level, messing with decay of notes, so i think some kind of input threshold would be useful. On the green ringer and the like there is some threshold from the diodes drop.
I find a series back-to-back schottky diodes on the input does the trick, the sound is more solid, but then there is some crossover distortion

[doubleg]

Prescription Electronics makes a pedal called the Clean Octave Blend.

I haven't been able to find any sound clips, but I did build one using a Torchy vero that didn't work.

i could post the vero and you could compare it to the schematic on another forum which can be found online to see if it's any good.

I built this octave pedal last week after reading this thread using the following schem Fuzzo posted: http://analogguru.an.ohost.de/001/schematics/Prescription_COB.gif

Instead of using a vero board i used this Rad Shack board http://www.radioshack.com/product/index.jsp?productId=2102845 and did my own layout using autocad.
(if anyone is interested i could post the layout, it's kinda crude but it made sense to me).

After working out all the bugs (I completed the board friday nite, took until Tuesday to get all the gremlins ) i have a few thougts about this particular octave pedal.
(only deviations i made from the schem-I used a 500K instead of 250K pot for the blend, as thats all i had lying around. also a couple of the larger resistor values I deviated due to having to add up values- however assuming +/- 5 percent tolerance of the resistors, i am theoretically within tolerance).

Anyways- thought 1:  Sounds best in front of a distortion.  the pedal itself can dial in it's own retro distortion sound, but if you play on a clean channel, once you get above the 12th fret or so on the high e, the volume drops big time. (not sure if this is inherent to the design or if i may have fried either one of the transistors or diodes?) im still dialing in the sound, but it seems if you lower the octave pot to about 40-60 percent( which lowers the distortion gain) ; nudge the blend pot slightly down- maybe 1/8 of a turn, and set the output volume to taste; run into the distortion of your choice, it seems to track more evenly as you play up and down the fretboard.

Thought 2: If you turn the blend all the way off (no octave effect) it can actully make a good clean boost.  Which presents a mild quandry for my rig.  I run a Sans-amp Tri-OD pedal straight into the poweramp in of my amp, I do not use the amp's pre-amp section at all. If I run a boost before my distortion, all it does is saturate the gain more instead of raising the db. level. So i run a boost after the sans amp and before the power amp to kick up my solos. After i built this pedal and noticed its boosting potential i had hoped to kill 2 birds with one stone-errr-pedal and use run this as my boost, and then when i wanted the octave effect just tweek a few nobs. Unfortunately it sounded like crud that way, if i dialed it a certain way than i would get the volume dropoff on the high notes, dial it another and it sounded like mud with fizz trails at the end.  So it looks like i'll have to stick with the separate boost pedal and put this one before the Sans-amp in my pedal chain.

Thought 3: I kinda wish i had soundclips to compare my build to, to see if the performance of my pedal is what i should be expecting or if i should try tweaking it some more.  All in all though, it was a fun build (my second build in all) and it was a good learning experience.

[Top Top]

the push me pull you by escobedo is one of the best, check that out, its quite clean

I'll second this. With the gain control down, you can get a pretty clean octave-up, and a lot of other cool sounds (sitar-like). It doesn't sound like litteral clean note doubling, but definitely not a "fuzz."

Playing chords up near the 12th fret with a low gain setting makes a really cool harmonic bell-like sound. I use this thing all the time when I record... such cool sounds.

[fuzzo]

I finished and I'm tweaking a bit my green ringer. I put a jfet boost to increase the volume output. A wired a 25Klin + 83n tone control linked to the second transistor's base. Works pretty good, the put the treble out like the tone control of guitar does , maybe reducing the cap values . At max (no treble) the level is reduced so the gain stage at the end is really useful.

Also I boosted it with a Gus NPN boost, good too ! a kind of fizzy tone with sustain (where the "clean" setting gives a really clear octave up efffect ) . Now I've to find what kind of booster I can add .

I would a gain control that gives no boost at 0, the stock sound coming from the guitar. I'm thinking about  building a jfet boost with a blend knob like gain, to mix between clean signal and boosted signal

What do you think about that ?

[brett]

Hi

I would a gain control that gives no boost at 0, the stock sound coming from the guitar. I'm thinking about  building a jfet boost with a blend knob like gain, to mix between clean signal and boosted signal

A simpler approach might be to build a common-source JFET booster, with a variable amount of AC bypass.  e.g. J201 with Rd=2.4k, Re= 1k pot (wiper to 22/47/100uF bypass cap).  That should give about 0-15dB of boost.  You could add a bypass cap (0.01uF, fc=7kHz) on the drain if you want to roll off some highs, or a small input cap before the pull-down resistor to roll off some bass (470pF for a 1M resistor).
cheers