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An important subject I want to discuss is noise. This because using effect pedals will have impact on the noise level of your rig and especially when using vintage effects. With the term noise I generally mean the signal noise ratio (SNR); the signal we do want to hear in relation to the signal(s) we don't!

What is noise?

Text by Ad van Dongen


There are several types of noise having different effect and causes. I have roughly classified them as follows:


1. HUM = a constant low frequency humming sound corresponding with the AC line voltage frequency of 50 or 60 Hz.


Main possible causes of hum are:

- not- or bad stabilized power-supply

- (current) overloaded power-supply

- inductor (single coil pickup or wah) picking up an AC magnetic field

- bad ground connection or shielding  

- nearby electroluminescent lamps (Neon & TL)


2. HISS = higher frequency constant noise, a sizzling sound. This is a random spectrum of all frequency; called white noise and is comparable to sound of sea waves.


Main possible causes of hiss are:

- bad transistors

- high frequency ripple of switching power supplies

- bad BBD chips (chorus & delay effects)


3 .CRACKLE = irregular medium frequency noise. It sounds like a fire place burning dry wood.


Main possible causes of crackle are:

- bad transistor, especially germanium types have this problem

- bad signal cable


4. Radio Frequency Interference (RFI) = receiving radio audio signals, mostly AM band on your guitar rig.


Main possible causes of RFI are:

- bad signal cable

- guitar pickups

- gain setting too high


5. SQEEL = a resonance of one specific frequency that can increase in volume and or frequency rapidly when not in control.


Main possible causes of Squeel are:

- not wax potted guitar pickups

- high gain setting of your guitar rig

- high treble setting of your guitar rig


6. MICROPHONIC'S = knocking sound when knocked on or moved. Can also result in feedback


Main possible causes of microphonic's are:

- not wax potted pickups in combination with high amp setting

- coil in Wah inductor

- bad guitar cable

- bad vacuum tube(s) in your amp