Sven's Guitar Site
Some Effect Basics
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I guess every guitarists how is playing electric guitar owns at least one effect or makes use of the effects biult in the amp like the spring reverb or the distortion etc.



There are alos serveral kinda of effects available on the market - stomp boxes and rack mount units. The rack mount effects are usually more expensive. Rack mount units are kinda made for the "professionals". They can be mounted in a 19" rack and are usually wired up at their back side. That looks definately cool ;)



Today there is an increasing number of digital effects available, since the "digital signal processors" (a microprosessor made for signal processing) and analog to digital (ADC) or digital to analog converters (DAC) are getting really cheap.



Some of the "old fashioned" analog effects have become vintage effects, they have a destinct sound and after everybody has gone digital, they have become popular again.



The draw back of analog effects is the degradation of the signal, that means that some noise is added to the signal. Usually, digital effects are clearer. Usually those digital effects have analog inputs and outputs. Thus the signal has to be converted twice: from analog to digital and after being processed back to analog again. That adds some noise, but usually, you canīt hear that. It takes pretty expensive devices to measure that degradation - usually the signal to noise ration (SNR) is better than 80dB (that`s 10 times less noise than a tape recorder produces). What can be a problem is a too hot input signal. Both analog and digital devices will start clipping. That sounds bad, since most effects aren`t made for distortion. Digital clipping really sucks.



The difference between digital and analog signal processing is very obvoius when you listen to analog and digital delays. In a delay, delayed signal is attenuated and fed back to the input again. This results in kinda echo. The input signal is repeated sereval times and the volume of the repeated signal is getting lower. Thus the signal passes the delaying stage of the circuitry several times, so the degardation is added up. Digital delays usually sound clearer than analog delays.



There are a variety of effects... some effects are influencing the frequency, some work time based, some are kinda filters and some distort. Here a brief description of the most impotant ones:

Distortion effects are pretty simple, they amplify the input signal over a certain level. The following stages can`t follow that anymore, so the signal is clipped. An extrem distotion would make a square wave out of a sine wave. The harder the clipping the less good the distortion sounds. Tube devices have a softer clipping, so they usually sound better than transistor based (solid state) devices. There is a nice little trick to get something like a softer clipping in transistor devises - they put a diode into the feedback loop of an OpAmp and get a logartihmic charateristic of the distorting stage (like in the Ibanez Tube Screamer). That`s not bad but can`t be compared to a real tube distortion.



Another sort of effects are filtering devices. An example for that kind of effect are equalizers. Filters are attenuating certain portions of the frequency band of the input signal and are amplifying other portions. There are two kinds of equalizers, graphic EQs and parametric EQs. Graphic EQs are those who have a certain number of faders each influencing a fix frequency. The position of the fader kinda represent the filter function (therefore "graphic" EQ). Parametric EQs have a number of groups of knobs. Every group of knobs is controlling a frequency band. One knob determins the frequency band, one is adjusting the level of that frequency band and (sometimes) one is adjusting the Q(uality). The higher the value of Q the narrower the frequency band that is influenced by that group of knobs. Graphic EQs are more familiar to many people, but a parametric EQ is more powerful (IMHO).



Some pre amps and even some guitars with active electronic in them have a mid(range) booster. That increases the level (boosts) of a certain frequency band (like 400Hz to 800Hz) about 6dB (or more). BTW: dB means dezibel, that is the unit of amplification. 6dB means the output amplitude is twice as high as the input amplitude. 12dB is four times, 20dB is ten times, 40dB is 100 times. That is a logarithmic calculation.



Another basic effect is the chorus. It modulates the frequency of the input signal and mixes it to the original signal. The result sounds like there is more than one instrument playing (not exactly).It's nearly unpossible to tune two guitars to exactly the same pitch. What a chorus does is like adding another guitar, that playes in exactly the same timing, but the pitch is slightly tuned up and down while playing. Some chorusses even have a knob for the pre delay. The chorussed signal is a little bit delayed (some milli seconds) to the input signal.



Detuners are slightly detuning the signal a certain amount. That`s usually some cents. A cent is a 1/100 of a semi tone. up to 5 cents are considered to be in tune. Detuners are usually digital effects and are sounding more natural than chorusses.



Pitch shifters add a signal to the input that is shifted up or down a certain amounts of semi tones. That sounds like two instruments are playing one in the original key and one like a 5th or an octave or what ever interval higher or lower. Octaves are no problem, since the addaed signal is in the same key. A 4th ot 5th still sounds kinda neutral (nevertheless interestin). All other signals can sound pretty odd.



Harmonizers are kinda advanced pitch shifters. You have to dial in the key you intend to play. The 2nd (or even 3rd) signal that is added by a pitch shifter stayes in the same key, so it doesn`t sound that odd.



Phasors and flangers belong to the same group of phase or frequency based effects. A phasor modulated the phase. A flanger is called flanger, because in the old days, that effect was achieved by touching the flange of a wheel tape.



The delay belongs to the time based effects. It is used for kinda echo sound. The input signal is mixed with a delayed signal, the delayed signal can be fed back to the input of the delaying stage again and the number of repititions are depending on the attenuation of the feed back. If you are using a stereo set up, it sounds pretty good just to add a signals delayed for some milli seconds to the original. In this case there is no signal fed back to the input.



The reverb is another time based effect. You can achive sounds like playing in a small room, a larcge room, a hall, a cathedral, a cave and many more. The spring reverb, that is built in the most guitar amps is pretty poor compaired to a real reverb unit. Anyway, it has a distinct sound and it`s better tha no reverb. Descibing the way a reverb works is pretty complex and I guess, I would have to get too technical (I have studied that stuff). Most reverbs have several modes like "Room1", "Room2", "Hall" etc. so they are simple to use. Some have up to 30 parameters to be adjusted like the size of the reverbant room, the hardness of the walls, the frequency degradation etc. Those are for more professional users.



A volume pedal is another "effect", but it doesn`t require any further explanation.



The wah-wha is kinda one band parametric EQ. It amplifies one frequency band and the frequency is determined by the position of the pedal. The result is pretty obvious. When you push the pedal, it sounds like "wahhh". It kinda imitates the human voice.



Noise gates can be kinda useful in addition to distortion units. Since distortion units base on amplification, they also amplify the noise in their inputs like the humming from the pickups etc. A noise gate just detects the level of the input signal and when it`s getting less than a certain level, the output is muted. That`s useful for recording. Nayway it can result in some unnatural sound when you start playing. You might hear a humming when you finger the first chord then it`s silent again and the gate "opens" when you start playing.



Another sort of amplification based effect are copressors and limiters. A limiter limits the volume to a certain level. A compressor compresses the dynamic (volume) range of the input signal. That results in kinda softer attack. Those devices are often used in professional audio processing.



I guess, that are nearly all effects I have ever used.



There is a recommended way to wire up your effects. The wah-wah should be the first effect in the chain, then comes the distortion unit, after that all frequency or phase modifing effects (choruses, detuners etc.). A delay should be placed after those effects and the last unit in the chain should be the reverb. The volume pedal sounds good either befor the distortion or after the distortion.


Anyway, this is just a recommended way of wiring up your effects, there is no reason not to try out other configurations.



If you have the chance to try a stereo effect setup, don`t miss that. Chorusses sound way cool that way and stereo reverb is awesome, too.



When ever I got a new effect I have made the same mistake, I have dialed in a too high effect level. Effects are like salt which makes a soup taste good, you have to use them carefully, too much screws up the whole tone. Too much chorus sounds really ugly and too much reverb blurs it.



Another problem with the tone adjustment is, that the sound seems to be different when it is played solo or when it is played in a band environment. I got into the habit of trying out a tone by playing along with some music (usually one of my midi files). A so called "smiling face" equalizing (high bass and treble, but low mids) can sound really cool, but when you try it out on band practice, it sounds pretty thin. IMHO the mids are an important part of the sound. It`s like the body of the sound. The lows make the punch and the highs are like the destinct voice of a sound.

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Last modified on Friday, 2. January 2009