arpeggiator pedal wanted..feasible?

[Paul Perry (Frostwave)]

A customer asked for this, but it's obviously a DSP problem.. so I said I'd mention it here, in case someone from a big company (hint hint) wanted to make it
Anyway...

"Hey Paul.  I've had this in my mind for a few years.  It's basically an
Arpeggiator pedal for guitar.  When a note is played on the guitar, it
repeats it numerous times at different specified pitches.

The pedal would have:
1.)  5 or more notched sliders that control the pitch - the more the better
2.)  Stop button for each pitch slider---arpeggiation will stop on the note
wherever the first bypass button is pressed
3.)  Volume level knob for each pitch slider
4.)  Overall Tempo slider to control how slow/fast the repeated
notes/arpeggio should be
5.)  MIDI, expression pedal inputs (maybe control tempo or overall
pitch?), and even storable presets would be cool although I haven't
thought about these features too much

I suppose this could be used for keyboard or loops, etc.....  An envelope
follower/filter effect would be a good feature also.

Visually, the closest I see it looking like is the new EHX HOG pedal.  I
have a Robotalk pedal that does a arpeggio, but it is very, very limited and
the arpeggio itself cannot be altered.

I would kill for this pedal!!!!!!!!!!!!!  lol"

[chokeyou]

its too bad the yamaha magicstomp confines the user to preset boxes. They pulled the harmonizer thing off pretty well with it, we need to start a magicstomp hackers group

[A.S.P.]

E-H 2880 ?

[RaceDriver205]

That 2880 is a nice piece of kit.
Doesn't the robotalk use a Sample&hold filter?
Pitch shifting is a realm this forum has not really approached yet, as this forum is predominantly about ASP effects. All the modern pitch-shift effects around are DSP based (the HOG, the PS-5), and there is very little DIY DSP information around. If anyone ever makes a VCPS (voltage-controlled pitch shifter) IC, that would be incomprehensively awesome.
That said, im working on a layout and design for the elm-chan simple DSP module, which reads an external voltage upon reset and pitch shifts an incoming signal a proportional amount. It may be possible to get it to repeat the measurement, but the fella who designed it is chinese and the notes are in engrish. If it works ill be sure to give him an email thanks, and ill be sure to "share the winnings" 

[Processaurus]

I've thought of hacking my boss super shifter to do this, because it sounds so cool in the harmonizer setting when someone twiddles the interval rotary switch while someone else is playing.  Theres an expression pedal input, that uses the TRS thing (+3.3v out on the ring, 0-3.3v back on the tip that the pedal reads to decide how much to shift the pitch).  Someone could plug a sequencer in there easily.  That would be the easy way out.  But I'd much rather hack the rotary switch, because its quantized, and in key because of their programming for the "intelligent" harmonizer function.

So I just popped the hood on the thing, and the 12 position rotary switch is actually a pot, with 12 detentes. 

It sure looks like its being used as a simple stepped voltage divider, putting out a control voltage, that I imagine is getting read by an ADC.  Heres the readings I took with my multimeter

position, starting fully counter clockwise, followed by voltage, followed by interval:
1.        0v  -2oct
2.     .22v  -1oct
3.     .55v  -6th
4.     .87v  -5th
5.   1.19v  -4th
6.   1.50v  -3rd
7.   1.84v  +3rd
8.   2.17v  +4th
9.   2.49v  +5th
10. 2.80v  +6th
11. 3.12v  +1oct
12. 3.34v  +2oct

The million dollar question (or at least $50 question) is if the microprocessor is happy getting voltages in between these, like if it rounds to the nearest one to quantize the pitch shift, if I were to attempt to disconnect the wiper from that pot, and insert an external 0 to +3.3v CV.  A tiny little external ZV style 8 step sequencer would be butter.  It'd be chickababy.  So would a S+H circuit.  I'm real excited about this idea, unfortunately I may not have the time for a couple months to hack it properly.  But someone should.  I think the chances of an experienced modder killing it are fairly slim, I'd definitely were an anti static wrist band with something this expen$ive though, and be extra sure to not short stuff out when powering it up when it was apart.

[Processaurus]

I thought I'd add that the mix control and key control on the PS-5 are the same way, each just sends a CV to the processor.

[SeanCostello]

http://www.diystompboxes.com/smfforum/index.php?topic=45497.0

I drive my Boss RPS-10 from a Roland SH-101, to get arpeggiated guitar sequences (although I haven't ended up recording with it, as it sounds a little too obviously "fake" for my purposes). The Boss RPS-10 is still fairly cheap in the US, and you can find a cheaper audio source to act as an arpeggiator. The RPS-10 is looking for an audio input, so it doesn't need to be an analog synth with CV outs or anything relatively esoteric.

As far as DIY pedals, you could use a Blackfin from Analog Devices, and create the audio path in VisualAudio. I am porting a pitch shifter from the SHARC over to the Blackfin in the next few weeks (I implemented linear and cubic interpolated delay lines last week, which was the main obstacle for the pitch shifter, flangers, choruses, etc.).

Sean Costello

[toneman]

Hey all,    just seeing this topic....
As i understand it,  on a keyboard, U can "arpegiate" between several held down keys .
How to do this for a guitar???   Try Roland VG8, or GR33.
The GR33 can arpegate between any/all of the 6 strings that are detected and pitch-recognized.
How to do this for a (non)Roland guitar???
I have NO idea and can offer nothing ...except ---  Good Luck!! 

[swt]

i did a really crude arpeggiator with a rocktave with ic and cap mods and a sequencer. it's analog!! ...did i said crude??

[toneman]

Hi swt,
But, is that *really* an arpegiator??
Since the Rocktave is only a one-note-at-a-time box, what notes were U generating for the arpegiator to play?
Was the sequencer U mentioned the actual arpegiator 
Maybe U actually have a "hammer on pegiator".... i just invented the term   
In doing hammer-ons, a lot of the time, U use an open string as a sort of "drone".
Then U push at a fret with a finger of the left  while picking, if necessary.
With a hi gain amp, U don't need to pick, but just do the hammering.
Always, the open string acts as a "drone".
That's the only way i can describe it.
If U used the 2 outputs of the Rocktave, divideby2 & divideby4, and, of course, got the Rocktave to track the
open note AND generate the lower octaves, U could multiplex all three signals with a sort of sequencer.
This would be a type of arpegiator, but would only arpegiate the octaves.
Is this kinda what U are doing/refering to??

[swt]

It is an arpeggiator, or at least sounds like it. you know there's a mod involving different caps and ic, for different intervals other than octaves for the rocktave divider from paia/anderton. so i've used tone god's sequencer to switch between those gates/intervals, and playing one note make whatever notes you choose from different switches/seq. there's some time/pop/who knows involved, 'cos' it was breadboarded just for fun, so noise, etc was interacting with the digital part of it, but it worked!.

[2wm]

i know this is an old thread but maybe someone is interested in brainstorming on this idea still.
i want an arpeggiator pedal that's programmable like this. i think it can be done without dsp.
i just don't know how to interface this circuit exactly.

http://www.casperelectronics.com/4017-gate-sequencer/

my thought was maybe to use a delay with infinite repeats and sequence the delay time. or maybe
a pitchshifter/delay. the 4017 chip can go up to 10 steps, it can be chained to another 4017 and
you can tie the reset pin to an output to vary the steps. maybe to more common musical numbers
like 2, 4, 8 or 3. you could use the outputs to drive relays or leds for optocouplers. and you can
vary the speed on the oscillator. i'd want to be able to do anything from slow repeating patterns
to video game style arps. one problem i see is matching the oscillator of the sequencer to the timing
of the delayed signal.

now sequencing the volume of the steps would make it much more complicated. i guess you could
have two 4017's running at the same clock speed with another set of sliders. or maybe just an lfo
running at the same speed controlling an optocoupler to vary volume but you'd have much less control.
or you could spend an evening thinking too much about this idea like i have.

--2wm

[2wm]

oh, and i think you'd want to gate the input signal heavily to prevent it from sounding like
a wall of noise.

[Processaurus]

That PS-5 thing worked, by the way.  It's great.  Right now I just have it hooked up to a trs jack, to use with the crummy boss ev-5, but I'm imagining hooking up a sequencer to it at some point.  I notice it takes it an instant longer than the other intervals to get up to the +2 octave.

[2wm]

i just bought a used boss rps-10 off ebay. it's got a keyboard control jack for the pitch shifter function.
so you just run an audio signal in to change amount of up or down pitch shift. i don't know how clean of a signal
you need but i'll experiment as soon as i get it to find out. maybe just a simple oscillator with a step sequencer
will work. how well does the ps-5 track with the expression pedal? i was thinking about doing something similar
with the rps-10 as i have an old volume pedal i bought to use as an expression pedal.

[galad]

you guys should read the whammy remote via MIDI thred...i describe how to do something like this with a digitech whammy

[MaxAllstadt]

There's only one unit I've ever seen that can work as an arpeggiator pedal with multiple programable steps.  The Boss GT 6-B bass multi-effects unit.  Use the funtion they call "auto-slap"  They discontinued the feature in the 8 series and the 10 series.  It only seems to exist on one model they ever made.

Auto-Slap gives you a 24 step sequencer with a four octave range, and multiple rhythm options.  Basically, if you pluck a note, auto-slap will play not just an arpeggio, but a melodic phrase.  You set each note in the sequence individually in the user presets. 

You have to know how to translate half-steps into intervals, because the way you set each pitch is by choosing how many half-steps up or down from the plucked note.  The parameter is from -24 to +24 half steps.  You can set each note as a soft note, a hard slapped note, a rest.  You can also set the note value from whole notes to 16th note triplets for each individual note.

I used it to create long and wide ranged arpeggios based on a giant lydian chord.  Another fun trick is to cross-map the expression pedal so that moving the pedal moves you through a few user presets.  I built a controllable arpeggio by making five user presets, each of which only shifted between two notes.  Each of the five stack up on eachother, and I can sweep through them with the pedal.

I have no freaking idea why they killed the feature.  Auto-Slap was crappy for creating auto-slapped bass phrases, but it's the best arpeggiator in a floor unit that you'll find.  Used ones can't be all that expensive either.