tremolo guitar effect feasability??

Hi, this is my first post - please excuse my newbness. I have only had my Arduino Uno for a day and have got it running/blinking - joy:). I have zero experience with microcontroller chip, but a little bit with analogue guitar pedals. So the first thing I can think to do with it is to possibly build a tremolo effect. The ability to precisely and easily control that blinking led is a very cool thing indeed :)

One way that the tremolo effect is achieved are spinning motor/speaker but more common these days in guitar amplifiers and effects pedals is with a optocoupler (or LED and LDR in a little tube/heat shrink to block outside light)

So my idea would be to build up a circuit on a bread board consisting of an input phono jack-hot signal to a LDR - straight out to an output jack which gets plugged into a guitar amp. The LDR sensor would obviously be coupled with an LED (maybe wrapped in black heat shrink) whose blink rate will controlled by the arduino. I would want to be able to add a couple of pots to control the blink rate i.e speed the LED comes on and off, and another to control how much light the LED produces?? The idea being that the signal will pass through the LDR (light dependant resistor) only when the LED lights. I could look at adding input/output buffer for the guitar signal-but will keep it simple to start with.

Does this sound feasible?? can anyone point me in the direction for controlling an LED with pots???Is there a good simple project out there on the web for doing this? I'm going to try it out this weekend - hope to be able to post some results. If anyone is interested let me know:)

Has anyone seen this done with Arduino?? I have built similar with 555 timer which requires more parts to control the LED but works well.

II geuss then it would be good to save presets and add a lcd to display settings etc - thats way down the track though and I,m probably biting off more than I can chew at this stage. cheers Steve

Sounds doable.

I have all of the parts for this and I am planning on building it as well. My idea is PWM to control the intensity of the LED (with analogwrite) and use that to control the photoresistor. Leaving the signal path entirely analog for the guitar.

Keep me updated. You can email me as well at my user name at gmail.

Good luck.

Wouldn't it be easier to use a digital potentiometer to make the existing signal from your effect chain a sin/saw wave? I too make guitar pedals and have thought about using my Arduino in a pedal, but haven't come up with any good ideas yet.

biocow: Sounds doable.

Thanks - thats exactly what I'm looking for.

Schmidtn: Wouldn't it be easier to use a digital potentiometer to make the existing signal from your effect chain a sin/saw wave? I too make guitar pedals and have thought about using my Arduino in a pedal, but haven't come up with any good ideas yet.

That makes a lot of sense. My very basic approach is coming from analogue only as I really don't know enough about Arduino yet. This version of a tremolo would just be analogue, and the Arduino acts as a big expensive 555 :)

As you point by using sine/saw wave your really have the ability to come up with new sounds-maybe in the realms of an autowah??. yeah I saw that dude from Make magazine on youtube who had modded a Big Muff pedal by doing similar - this sounds cool

Even playing around with just about any guitar pedal and substituting digital pots - just think of the "potential" :0) (Ok that was a baad pun) But to my way of thinking, a microcontroller would then give you ability to re-call settings as presets coupled with an lcd display-instead of having to twiddle all the knobs to get a sound - lets face it that isn't that practical on stage. Imagine with the use of digital pots - you could recall snapshots (presets) instantly-which might just be a few lines of code in your sketch!!!

I definitely think theres a lot that can be done with Arduino and analogue guitar effects - now I just gotta figure out how to do it. cheers

I was thinking of that video earlier but didn’t go digging for it.

Hey that was pretty neat, kind of what I was thinking but he actually did it.

So are you avoiding digital for tone reasons? I know a lot of people are all analog this and true bypass that but to be honest I don't get what all the hubb bubb's about. I run digital pedals into a tube amp every day and think it sounds nice.

I know this thread kind of petered out, but I'm still working on mine. If you watch the make vid, you can hear all sorts of weird remnants from the digital pots. You want to use audio grade digital pots and then it gets a bit tricky to make them do the right thing and not add extraneous noises to the chain.

Insofar as recalling setups, etc... there are some interesting chips from molten voltage that do different LFOs and tap tempo. Very cool and reasonably priced:

Their newest thing, does a lot

I could see using the arduino in concert with these, but I still have my project which is still in progress. :.

I've just got an arduino uno, and my first project is to build a similar tremolo. I'd seen the molten voltage PIC's before, thought they were cool, so I'm basically going along the lines of it.

So, what I'm using the arduino for is the LFO waveform synthesis. The actual audio path will remain analogue, probably with TL072 op-amps like the tremulus lune, although TI were very kind to send me samples of their TLE207's (drop in replacements with lower noise factors) so I could use those. I figured I would use an opto-coupler with the transistor section shunted to ground so it would be more like modulating a digital potentiometer.

So far I have working:

tap tempo input - tap a button and it figures out the tempo you're tapping at. PWM waveform output using the timer2 interrupt function ( (can go over 1kHz, if you can tap that fast...) Supports arbitrary waveforms - just load them into the program as 256 comma separated 8-bit integers. I use matlab to generate them... Tempo modifier - I've hooked up a pot to one of the analog inputs which allows you to select frequency multipliers of 0.5, 1, 1.5, 2, 4. Could obviously go to much larger factors. Waveform selector - using another pot on the analog input you can select the waveform, sine, triangle, square, perhaps swells, random, beat functions (ie four square waves where the amplitude of the first is greater than the rest for accentuation) additional digital sync outputs - flash an LED, drive an opto-coupler for switching other fx that can take a tap-tempo pedal (such as the boss dd-7)

I've not hooked it up the tremolo circuit yet, but on my scope the waveforms look great (well, you need to filter them first obviously, check the link for a good schematic for a 12kHz low pass filter). Whats nice is that the output is controlled by the timer interrupt function and not the main loop function, so you can use the loop for control without fear of the waveform losing sync.

I will, once I get it to v1.0 post all code etc and probably an instructable...

I think I will have another go. I got my basic tremolo working which I code named the "under the hat" tremolo - cause when I wanted to hear the trem effect I just put my cap over the arduino/breadboard :)

I used this code - with 2 x 10k pots controlling the led which was on one side of the breadboard (board has 2 rails)

On the other side of the breadboard was the LDR and jacks.real simple - BUT......

int potPin1 = A1;
int potPin0 = A0;
int ledPin = 9; 
void setup() {
  // declare the ledPin as an OUTPUT:
  pinMode(ledPin, OUTPUT);  

void loop ()
  analogWrite (ledPin, analogRead (potPin0) / 4);
  delay (analogRead (potPin1));
  analogWrite (ledPin, 0);
  delay (analogRead (potPin1));

There was a bunch of noise coming from the pulse that made it kind of annoying. Trem effect was kind of like an old 70s amp with built in trem that I once owned - nice and subtle. after a while I shelved it as I couldn't get rid of that noise - making it useless for recording/or live etc.

Anyways I found this from Dano at Beavis and theres some clues about using a filter to get rid of the noise - so I think I will try again...

Was wondering how any of you other chaps went?? Anyone got this workingproperly???

I need to know which product is the best from the ones listed on the site?