Guitar type Tuner


I’m trying to make a tuner for guitar and analog oscillators. The main problem is I’m trying to find the best way to make a sweet spot that registers as ‘in tune.’ Right now I am always sharp or flat and in tune is rapidly flashing. The only way I get the solid green light is with dialing it in digitally.

Suggestions and feedback are welcome.


Updated 8-5-2018

I guess this is open beta.

Audio Tuner proto 3.audulus (60.5 KB)

Please download this version, I put some slew limiting on the display so it flickers less, and I added an internal trim pot to allow for different tolerances.

I would love to know if you can use this to tune a eurorack oscillator or a stringed instrument like a guitar.


I have downloaded and tested the prototype and have tested it with my Minibrute2S patched through the ES-8 in my eurorack and monitored the tuning through speaker to UltraTuner app on my iPhone.
I put a value indicator on that internal trimpot and found that a value of approximately .870 there was midpoint of when the notes indicator would switch. It tracked properly across 5 octaves.
BUT it shows Blue LED for flat when it should be green and I’ve no clue where to make an adjustment for that to be Green and in tune.


@Ron_H Thank you for the feedback!

It is possible that the sample rate influences the tracking or that the analog oscillator of the mini brute 2S isn’t perfectly calibrated. I used the tuner in a synth jam to keep my DPO in tune and I noticed that it definitely tracks a little off from 1 volt per octave.


Probably could have also checked it earlier with my Keystep and a VCO (checked 1v/oct tracking with my scope beforehand) …trim still set the same but it seems to want to almost turn on that green ‘in tune’ LED. Adjusting the Flicker filter just don’t quite get it there.


This seems like a significant tool for Audulus. Would love to see this get nailed down.



Audio Tuner proto 3.audulus (60.5 KB)

Ok, I added a noise gate on the input so that the display doesn’t freak out on the noise floor of an audio input. Adjust as necessary.

I’ve tested this quite a bit with eurorack oscillators, but not yet with actual guitars. But it’s getting there. Once I can reproduce the Blue LED bug and borrow a guitar to tune, I’ll move the thread to Modules.


A good tuner will probably also have some LPF’ing in the audio path to emphasize the fundamental?

Might even be able to make it dynamically change the cutoff depending on the input value so you can really hone in on bass notes while opening the filter for higher notes when you want to tune there.


Good call with the LPF in the signal path, I will give that a go.


Most commercial tuners either “guess” at the note you’re trying to tune or have you set it manually and then use some type of notch filter centered on the desired frequency to suppress all the harmonics.


Would that be a notch filter on the fundamental?


I should have said band-pass not notch. A band-pass centered on the fundamental helps to reject the harmonics and other resonances. My hammer dulcimer is box of resonant strings and finding a tuner that works is a real challenge. Also bear in mind that a plucked string changes frequency slightly as it decays so “in tune” is somewhat a matter of opinion.


I like how the hammer dulcimer test really upped the anti here. “No…not…the…dulcimer!”

The thing is, if you end up making a really good tuner its totally worth it, as almost everyone here would use it often in one way or another I bet.


I love my hammer, but it’s a bitch to tune. 72 strings and when you hit one they all resonate to some degree. Add the body resonance, and you can imagine what the tuner input looks like. I’m currently using a BOSS TU-15 which works fairly well. The best iOS tuner I have found so far is insTuner. I’ve tried a bunch and this one seem to be the best at isolating the string I’m trying to tune. Has all the bells and whistles as well. Different temperaments, a selection of display styles, ability to choose the input channel etc. PST (Precision Strobe Tuner) also deserves a mention. A different approach to the display, but also very good.