Updated May. 17, 2022

AC Noises Urla

The AC Noise Urla is an uncompromising new stompbox from one of the most interesting pedal companies to emerge as of late. It’s an uber-tweakable CMOS fuzz in front of a dual resonant filter, with separate footswitches for each.

At a time when most pedal builders seem to jump through hoops to figure out how to make fuzz pedals more responsive, the Italian folks at AC Noises challenge the trend, giving us a digital fuzz that, since it produces ones and zeros, creates an output consisting in square waves with no adjustable gain. This means that when you play this circuit, you don’t get subtleties, you just get a consistent screaming fuzz (“Urla” means “scream!” in Italian).

Fortunately, a Blend knob lets you reintegrate some of the clean signal, which helps moderate the insanity and bring back some dynamics.

The resonant filter section is a faithful replica of the analog filter section of the glorious Korg MS-20:s an High Pass filter connected in series with a Low Pass one, both adjustable with their relative controls of Cutoff and Peak.

The three big knobs on the top of the pedal allow you to precisely set the level of fuzz, filter, and clean signal, while the toggle switch lets you control either filter’s cutoff value with an Expression pedal, for effects from wah-like to synthy.

Have a listen to this insane pedal in the videos below.

AC Noises Urla, Builder’s Notes

“Urla” is an Italian verb which means “scream” in second person imperative (tu, urla = you, scream).

A loud, aggressive and experimental device which consists in 2 effects in 1 pedal unit, the URLA is a CMOS fuzz in front of a synth-based dual resonant filter.

CMOS fuzz

A CMOS chip works with digital logic (1, 0).
Compared to the transistor based fuzz circuits (both germanium or silicon), in a CMOS fuzz there is no “in-between”, no “dynamic range”, no “vintage tone” or anything like that. There are just 1s and 0s, so no matter which kind of waveshape you put into it: the output will always be square wave with no adjustable gain neither since the square wave is as distorted as it can get.
The URLA obviously makes no exceptions and it provides an overdriven, brutal, glitchy and gated fuzz sound with a decay that dies abruptly (but still allowing to sustain each note thanks to a bass boost stage that we put at the very beginning of the signal path).
It offers 2 controls: VOLUME and BLEND.

VOLUME (fuzz)

Adjusts the output level of the fuzz.


As the name suggests, this control allows to blend the fuzz sound with the original signal placed in front of the URLA. Clean guitar tone is probably the most basic example in that sense but no doubt the bravest sonic adventures could find plenty of different as exciting solutions (e.g. as “wall of sounds” enthusiasts, we do love to place a shimmer reverb in front of it or some modulation as well to create different kind of textures). Being a fully analog jFET blend, it goes from almost completely DRY (counterclockwise) to 100% wet signal (clockwise).


This is the second effect placed in the internal signal chain of the URLA and it consists in a faithful replica of the analog filter section of the glorious Korg MS-20, simply our all times favorite vintage monophonic synthesizer.
It’s an HIGH PASS filter connected in series with a LOW PASS one, both adjustable with their relative controls of CUTOFF and PEAK. Also, we added a dual potentiometer to control the VOLUME of both, which is pretty useful in order to dial with other output levels in chain (including the internal FUZZ placed in front).

VOLUME (filter)

Sets the output level of the dual filter.


These knobs allow to decide where the frequencies (high ones by LP, low ones by HP) have to be cut. No doubt they’re the most exciting controls of the URLA.
We placed those on the external sides of the pedal’s surface exactly because of that: you’ll love messing up with those as much as possible by exploring the wild excursions of both. In fact, depending on the place of their relative PEAK knobs, they can go approximately from 0hz (so you’ll mute your signal completely when at least one of their respective knobs are fully closed) to 15kHz.


While cutoffs allows to remove frequencies (harmonics) from the incoming audio signal, their respective resonances allow to have an additional controlled amplification of the cutoffs frequency, creating a secondary peak form and coloring the original pitch.
The resonances of the original Korg MS-20 are well known for their pretty wild and loud nature due their tendency to create a microphonic feedback at extreme settings. URLA makes no exceptions, so USE THESE KNOBS CAREFULLY: depending on the cutoffs positions (especially the one related to the LP since it’s the last one in series) they really make your amp scream and/or boost low ends massively when set at high levels! For that reason, we highly recommend to keep the filter volume as low as possible when starting to dial with this effect.


We’re not going to lie: if you’ll not play the URLA with an expression pedal (by using a TRS cable) to control the cutoff of your favorite filter (HP or LP it’s up to you: just place the EXP toggle switch where you prefer), you’ll probably miss more than the 90% of the fun.
For that reason, our friend Luca Romanelli from Mastro Valvola (the same guy who wrote the code for the RESPIRA’s shimmer) designed an expression input which works correctly with ANY expression pedal on the market.
But there’s more: when the expression pedal is plugged into the URLA, you can still set the minimum (the starting point of the parameter you want to control with the expression pedal) by adjusting the relative cutoff knob.

As aggressive as experimental-friendly, URLA is our tribute to all the industrial, noise and alternative artists/records that made our world a better place to live.

Switching System: true bypass managed by soft switch + programmed relay.

Power: 9v center negative. Current draw: 100 mA minimum