This article may be useful if you hear a buzz, whine, hiss, chatter, or any number of other noises that have been known to affect audio equipment like Quad Cortex. 

The most common roots of the problem could be bad wiring, defective ground installation, or just a noisy electronic environment. Whatever the type of noise you’re hearing (and whatever the cause is), here you will find a few tips to improve the quality of your signal. 

Some noise is inherent, such as when you turn up gain knobs or increase input levels. It’s part of the audio-hardware and the best way to improve it is to tweak the audio settings or re-order the device blocks in a better way.


Background Hiss

Quad Cortex has been engineered with an emphasis on performance for several real-world scenarios, including using it in conjunction with external equipment (amplifiers, monitoring systems, PAs, etc.) For this, an ungrounded, isolated power supply provides the best noise/grounding performance.

This means that the Quad Cortex receives its ground/earth reference potential from whichever piece of equipment it may be connected to, which greatly reduces the likelihood (or even the severity) of ground loops/hum.

In the case of two electrical systems being connected, slight variations in their ground/earth reference potentials can result in a ground loop. These variations are quite common in audio systems, and the surfaced ground loops manifest themselves as an audible (and quite familiar!) 50Hz/60Hz hum.

If the Quad Cortex is used with headphones (without any other equipment connected), some instruments’ pickup interference can modulate QC’s ground/earth line, which will result in perceived hum. This is particularly true with passive, single-coil pickups.

However, it is possible to provide a ground/earth connection to the Quad Cortex by connecting another piece of equipment to remove/reduce this noise. This can easily be done by using any of the inputs or outputs found on the rear of the QC and said external equipment does not need to be powered for it to provide the reference needed to eliminate interference.


Ground Loops

A ground loop occurs when there is more than one ground connection path between two pieces of hardware. The duplicated ground paths form the equivalent of a loop antenna that picks up interference currents very efficiently. 

The main cause of unusual audio noise is the "ground-loop", simply because it’s so easy to create. The most common manifestations are a loud buzz or hum coming through the speakers or headphones. It typically occurs when one or more pieces of hardware are plugged into the AC (Alternating Current) at different locations, then connected together by electrical (versus optical) signal cables whose shielding is connected to the ground.

In the simplest terms, this creates a single-loop antenna that just loves to catch various types of noise via electromagnetic induction. 

How to solve it? 

Anything that breaks the loop will remove the noise immediately, and the easiest way to do it is to power the Quad Cortex and audio hardware through a single AC socket. Simply plug all your audio equipment into a single power strip, surge protector, or power center and plug that into the wall outlet.  

Powering connected hardware from the same AC socket eliminates most ground loops. If you still get noise, check if the electric installation at home has its own ground connection.

Also, external hum-eliminators reduce ground-loop noise safely.


Headphones Hiss

Under certain circumstances, the headphone's output can amplify the hissing noise coming from the Overdrive block, Amp blocks, and different gain stages in The Grid. 

How to solve it? 

An easy way to increase the volume difference between the noise floor and the output level is by decreasing the HP LEVEL to -5dB then compensate with the Volume Wheel. This can be improved even more by adjusting the Headphones Mix in the I/O Settings


Electric Noise when Quad Cortex is turned Off

There is a chance to hear noise when Quad Cortex is turned off and the powered monitors connected to its XLR outputs are still working. 

How to solve it? 

Turning off first the monitors or amplifiers connected to Quad Cortex is a good practice. 

For smoother switching, the XLR Outs use optical switches to lift the ground, and the default mode when these are not powered is open, so the grounds are lifted when the power is turned off.

If you’d like to keep your monitors powered on and connected to Quad Cortex when it is not in use, using the STANDBY feature will solve the issue as the ground state will remain. Press the Power Button to access the Power Functions and select [STANDBY]. All audio outputs will be disabled and the screen will be turned off. 

STANDBY mode also had the advantage of having immediate boot-up.