#1
I'm looking to make/find a pitch shifter that can replicate Tom Morello- Style pitch shifting without buying a whammy. I've looked into several models on generalguitargadgets.com, and none of the sound samples seem to be what i'm looking for. I've also read about the Boss PS-5, but i don't really want to spend that much money.

Anyone have any experience with their own pitch shift pedals?
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#2
Dude, GGG doesnt have any pitch shifters. Phase shirfters are Phaser pedals. You wont be able to build a Pitch Shifter because its digital. So you will have to buy it.
#4
Octaves can only go to the same note as you play but one octave higher, or one octave lower (different pedals for each if you want analog). Pitch Shifters can change a note into any other note, not just the same note.

Also, analog octaves (the kinds you can build) are mostly fuzzes with octaves. Analog, theres not an easy way to get a clean octave.
#5
A pre-made pitch shifter would be the best, as Morello uses anything from fifths to octaves to two octaves.
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#6
Quote by call1800ksmyazz
Octaves can only go to the same note as you play but one octave higher, or one octave lower (different pedals for each if you want analog). Pitch Shifters can change a note into any other note, not just the same note.

Also, analog octaves (the kinds you can build) are mostly fuzzes with octaves. Analog, theres not an easy way to get a clean octave.


do you know of a hard way to get a clean octave? if so do tell, ive been looking into them lately..
#7
^-Not exactly. I went into searching a while ago. I found a supposed Clean Octave Up but I never got it working. I ended up going for the Bobtavia which is a modded Octavia. Most octaves use a small Audio transformer.
#8
Quote by call1800ksmyazz
^-Not exactly. I went into searching a while ago. I found a supposed Clean Octave Up but I never got it working. I ended up going for the Bobtavia which is a modded Octavia. Most octaves use a small Audio transformer.


Isn't it nice to see GB&C electronics people finally acting civil? I learnt Ohms Law at TAFE today, I think I'm almost ready to start building amps
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#10
Civil? Hmmm..... What was the outcome of all that stuff with the stickies btw? (if I'm allowed to ask without being censored)

Anyway, it is possible to build an analog pitchshifter, but whether it's cheap or not depends on whether you have the tools etc. A few months ago I wanted a whammy pedal but didn't want to splash that amount of cash (although I bought one eventually).

To transpose a note by an octave, you have to double the frequency, ie A @ 440Hz becomes A at 880Hz. The digitech whammy uses a digital processor with a very high clock speed to digitize almost every part of the input signal. Some parts, like high frequency overtones, are lost because they can't be completely captured. The processor analyses the input and works out the frequency. It rebuilds a new signal in real time. First it starts with a basic sine wave of the correct frequency, then uses linear extrapolation to add parts from the original signal to the new one, resulting in a tone that is pretty close to the original.

The best way to do this in analog is to use a frequency to voltage circuit. This is what synths and early keyboards used. It measures the frequency and outputs a voltage that is proportional or has some relationship. If you wanted to do this yourself, you'd have to limit it to chromatic changes. This voltage is then fed into another circuit that adds a certain amount to it, depending on what interval you've set it at. This goes to a voltage to frequency converter which outputs a new signal. This only really works if you have a perfect sine wave to start with. With a guitar signal, which has many overtones present, you have to use heavy companding with a dynamic filter inbetween. Of course you only get a pure sine wave at the output, which won't sound much like a guitar. You need to add another variable compander at the output to make the envelope sound like that of a guitar.

If you don't want pitch shifting, just a simple octave up, you need to use a voltage multiplier. Traditionally these would use a high speed triangle wave clock to modulate two input voltages through standard opamps. Howeverit won't work for a changing signal like a guitar's output, since the frequency quickly outpaces the clock's. The simplest way is to use JFETs to multiply the input by its inverse, giving you an almost perfect octave up. It also works for distorted signals so it can go anywhere in the signal chain, and has the cool side effect of bringing out things like the harmonics from your pickups. Its way better than a standard fuzz/octave that uses a transformer in that you aren't getting the modulus of the signal (which has double the frequency but is distorted).

If you want any sort of diagram of any of this, just say and I'll give it a go.
Dave
#12
Quote by call1800ksmyazz
^-Not exactly. I went into searching a while ago. I found a supposed Clean Octave Up but I never got it working. I ended up going for the Bobtavia which is a modded Octavia. Most octaves use a small Audio transformer.


Not the Octavia. I'm talking about the Roger Mayer one.

I'm building one right now, but my soldering iron broke down (how the hell does that happen anyway?), so it will be a while before I can continue (I tried my dad's 40 watt one....no success).
#13
Quote by Wyld Stallyn
Civil? Hmmm..... What was the outcome of all that stuff with the stickies btw? (if I'm allowed to ask without being censored)

Anyway, it is possible to build an analog pitchshifter, but whether it's cheap or not depends on whether you have the tools etc. A few months ago I wanted a whammy pedal but didn't want to splash that amount of cash (although I bought one eventually).


If you want any sort of diagram of any of this, just say and I'll give it a go.
Dave



yes, make it so
#14
If you want any sort of diagram of any of this, just say and I'll give it a go.
Dave


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#15
A good clean octave up effect is the electro harmonix POG-Polyphonic Octave Generator. It is very pricy ($300) but it can do one or two octaves up, and one octave down. If you havent seen it, is basically a bunch of slider switchesWhere you can mix together your guitar signal, octave up 1, octave up 2, octave down 1, and detune switches for each one. You can select as many or as few of these effects as you want at a time. As the name suggests, this thing is polyphonic which means it can handle chords. I've demoed it at the shop, and it has a very natural sound to it. It can make you sound like a bass, a twelve string guitar, an 18 string guitar, a tenorguitar, a soprano guitar, an organ (all octaves on half mix), or some cool synth sounds. It can sound really crazy if you play a twelve string guitar into it. Like is said, pretty expensive, but as soon as I get some money together, I'm getting it.
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#16
Quote by SG Man Forever
...It is very pricy ($300)...
...I've demoed it at the shop, and it has a very natural sound to it. ....


hi SGMF,

$300 seems dirt cheap for what you've described.

i saw a write-up on a POG awhile back, but i thought the cost was much higher. maybe they reduced the price.

seemed like it was worth looking at.

i think you convinced me.
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#17
This man is a GOD. I applaud your knowledge.

Thanks, I think.
yes, make it so

Thy will be done...
Anyway, here's a quick schematic of how you could make a perfectly clean octave up. There's a few buts missing, like maybe a buffer at the input and output, but it works in theory. I'm sure R.G.Keen had a schematic that used the same principle, and it probably had all the extra bits thrown in.

Starting at the input on the left:
signal goes through a pot and capacitor to make sure there's no dc offset to it. Then the first jfet produces two versions of the signal. First is just a copy of the original, second is inverted or shifted by 180 degrees. These signals go into two more jfets which amplify and multiply the signals together, giving you a perfect octave up at the output.
Obviously using the standard transformer or diode fuzztave circuit that Kerry mentioned gives a more vintagey sound since that's how it used to be done.
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#18
WOW
that sir is awesome, its now officially on the 'to do' list

and it should work for what i want, i already have as much vintage fuzz sound as i need, the octave is the final bit ive been looking for.

now, as for a buffer, do you think using a tubescreamer input/output buffer would mesh nicely?
#19
Yeah, I think really any standard buffer on the input and output should work. You'll probably have to play with the input level to stop it clipping, and maybe roll off the tone afterwards.
#20
About that POG, though, I might Recommend you try the HOG too. it's like the POG but more.
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