Is my idea feasible?

[still-young]

Hello, for my Engineering HNC I have to do a project, and I'm planning to make an effects pedal for mine. It has to be relatively complex; my current idea is a pedal that you can switch between chorus, phaser and flanger, with an expression pedal that controls the rate. (I had another couple of ideas, a Delay, Chorus and Reverb pedal with an expression for delay time; or a bass wah with autowah built in and switchable ranges for the wah). They might sound overcomplicated, but I don't want it to be too simple as it's a HNC. I'd prefer to do one of the first 2 as I'm not a fan of Wah really. Whichever I do, it's primarily going to be for bass. Are they doable?

[still-young]

Ooh, what could do I do differently with a ring modulator? Like a wah pedal style one? I love ring mods, I forgot about them.

[antonis]

Are they doable?

Everything is doable...!!!
(not by me, of course..)

Maybe you should first decide for the "complexity degree" of the project..
(i.e. indepentend circuits switchable by a humble SPST switch or interacting complicated circuits switchable by continuous variable analog electronic switching..)

[ElectricDruid]

my current idea is a pedal that you can switch between chorus, phaser and flanger, with an expression pedal that controls the rate.

In general, you could solve this by building three pedals and switching between them. The expression pedal part I'd try and do by adding voltage-control to the "rate" part of each circuit and then using the expression pedal as a CV source. But I have a lot of background with analog synths so thinking in terms of "CVs" and voltage-controlled-X's is what first comes to mind for me. There are plenty of voltage controlled LFO designs in the world you could use. There would be other ways too, I'm sure.

A pedal that switches between chorus and flanger would be *relatively* easy to do, since chorus and flange are so similar in the way they're produced. In this particular case, you might not even need two separate circuits - you could use just one and tweak it. The Phaser still needs to be a thing on its own though.

HTH,
Tom

[digi2t]

Ooh, what could do I do differently with a ring modulator? Like a wah pedal style one? I love ring mods, I forgot about them.

Already done. Look up Snarling Dogs Mold Spore.

[Tony Forestiere]

Ooh, what could do I do differently with a ring modulator? Like a wah pedal style one? I love ring mods, I forgot about them.

Already done. Look up Snarling Dogs Mold Spore.

Paul would tell you to "Plagerize" "Do some research". 

[Transmogrifox]

Is DSP within scope of project or must it be analog?  You could make the project suitably complex by making a board with a DSP, CODEC and some ADC's (for control inputs).

The advantage of the DSP is you can have the expression pedal modify the effects in any imaginable way...even morphing between different FX...adding envelope control.

As RG says "A Simple Matter of Programming".  Honestly there's so much code out there for phasers, flangers and choruses the hardest part of the project would be doing drivers for the ADC's and CODEC.

If you do this analog then it appears you have good suggestions.   It's a feasible idea...simple in concept but a good amount of time with a soldering iron.

[still-young]

It doesn't have to be analogue, but anything digital/coding goes completely over my head, I don't have a clue what I'm doing. Is it difficult?

Glad to know the idea is feasible though. I am attracted to doing something with a ring mod too now, but I want it to be different. Is there anything different I could do?

Thanks for the help so far guys.

[Transmogrifox]

It doesn't have to be analogue, but anything digital/coding goes completely over my head, I don't have a clue what I'm doing. Is it difficult?

It's a steep learning curve but feasible.  My senior design project at university was implementing acoustic direction sensing (using 2 microphones to estimate the direction of a far-field sound source).  We modeled the algorithm with MATLAB and implemented it on an Analog Devices DSP demo board using assembly language.  I found assembly, even though it is more tedious to write, is more intuitive to an analog/hardware mind.  It was several years after that I invested the time to learn how to use C & C++ effectively.  Getting to where I could create my own guitar effect from scratch was about a 3-month process.  I started by compiling and running an open-source guitar FX processor on a Linux box, then reading the code until I could understand it.  Then modified the code to change things...then I was ready to make something from the ground up.

Glad to know the idea is feasible though. I am attracted to doing something with a ring mod too now, but I want it to be different. Is there anything different I could do?

Thanks for the help so far guys.

I once had a ring mod-ish (it was a PWM chopper-modulator) on a breadboard.  I had it so I could assign envelope control to either (or both) modulation depth and frequency.

One time messing with it I built an envelope filter on the board and realized if I ran the envelope filter into the ring mod with the ring mod frequency set at around 750 Hz I got a robotic "yah yah" effect instead of the "wah wah" sound usually you get from the envelope filter.

The envelope modulated ring frequency was pretty wild too.  The oscillator was based on this:

You can replace R6 with a PNP transistor with emitter resistor and use the base to drive it as a constant current source.  That allows you to adjust the oscillation frequency over a very wide range. 

My circuit had these parts:
A) PWM generator just like schematic above.
B) Ring frequency oscillator (same sawtooth generator but with the transistor current source for frequency mod)
C) Voltage-controlled triangle oscillator.  Similar to sawtooth generator, but also a voltage-controlled current source replacing D1 for controlled discharge rate.  The CV was chained to the 2 transistors in a complementary current-mirroring setup to make the rise and fall rates move together (I think I may have also experimented with an offset circuit to make it possible to go asymmetric).
D) Envelope generator which I could use to drive either oscillator amplitude control and/or frequency control.

The triangle oscillator portion was optimized for low frequency operation.  It could go from sub-Hz up to about 100 Hz.  Great for tremolo or sub-octave effects.  The plain ramp oscillator was optimized for higher frequency stuff, like up to 10kHz, but I think I was able to still get 10Hz oscillations out of it.

Either way you can add the two oscillators so you can combine a tremolo throb with crazy ring stuff, or sub-octave and "DTMF" sorts of sounds.

Finally that audio-frequency oscillator was fed into the PWM modulator from above schematic (ignoring part values).  The PWM modulator was adjusted to operate at around 220 kHz if I remember correctly.

Then I used a chopper modulator as the voltage-control element.  Although what I used was different, I could easily have simplified and done the same thing with RG's chopper:

The "switch" would be an analog switch like SSM2404 which doesn't have excessive clock feed-through.

The nice thing about the polarity reverser is that 50% duty cycle at frequency well above audio range results in nulling the signal (output is silenced).  That way you can do full AM modulation like a true ring modulator or you can do more like a tremolo and run from 0 to 50% duty (or 50% to 100%) or even just fix the PWM with a pot and use if for a volume control that has the ability to give you non-inverted or inverted output.

So if you want something different, see what you come up with by combining those building blocks.  What I had on my BB was really wild.  I wish I had taken the time to build it into a box.

[BubbaFet]

I'm reminded of a 'Dilbert' comic from long ago....

and I am reminded that we all have to start somewhere...

http://dilbert.com/strip/1999-02-17

[still-young]

Thanks for the great reply Transmogrifox, really really helpful.