Described below an effects order is a result of our experience and serves to achieve the best tone (assuming that the effects are used with proper signal level). At the front (between the guitar and the amp input) should be placed the following effects (starting from guitar side): wah-wah, compressor, various kind of distortion, overdrive and fuzz effects. In the FX loop or just next to distortion should be placed the following effects: phaser, flanger, chorus, tremolo, octaver, pitch shifter, delay, reverb.

Many guitar amps features the FX loop for connecting the effects. Usually it is the serial loop (see the dictionary) and for sure the delay and reverb type effects should be connected to such loop. In case of using the stompboxes connected to the looper it is needed to use together with the GSC-2/3 the looper controlled via MIDI e. g. Midi 4x LOOP M4L. Thanks to that we avoid the grounding loops problem and it is possible to place the effects near the amp.

MIDI – it is the interface for music equipment usage. It enables transmission of commands, messages and other occurrences between connected devices. Practically two kinds of commands are used in guitar’s controlling systems: Program Change (change the program) and Control Change (change the control parameter). Interface sends the commands in one direction from MIDI OUT to MIDI IN. Thanks to the transoptors it doesn’t cause the ground loops. Most of 19” rack effects features MIDI IN input that enables to control them. MIDI foot guitar controllers (e.g. GLAB GSC-2/3) feature MIDI OUT output and can be programmed to send the Prog. Change and Contr. Change commands. Thanks to addressing via MIDI CHANNELs one controller can control number of devices (up to 16).

MIDI CHANNEL – No. of the channel (from 1 to 16) on which is sent given command. Receiving device can receive the commands on every channel (OMNI mode) or on the previously chosen channel. In some devices the receiving channel (MIDI IN CHANNEL) is set independently from sending channels (MIDI OUT CHANNEL).

Program Change command (PrCh) – MIDI interface command transmitting the No. of program (preset) to recall (from 1 to 128). The example of using Prog. Change command is recalling the preset/sound in the multi-effect controlled via MIDI

Control Change command (CC or CtrlCh) – MIDI interface command transmitting the No. of controller (from 0 to 127) and the controller’s value (from 0 to 127). Receiving devices treat the controller’s number as the chosen parameter and they treat value as setting/adjustment of the parameter. The value of the controller can work in continuous parameter mode from 0 to 127 (e. g. volume adjustment), in limited range (e. g. delay time in delay type effect from 5 to 127 x 10 ms) or even control ON/OFF type parameter (e. g. from 0 to 63 – effect off and 64 to 127 – effect on)

MIDI THRU – it is MIDI transmission output socket with a copy of the signal which comes to device’s MIDI IN input. Thanks to that one talking device can control number of MIDI devices. In some devices it is possible to set the MIDI OUT output on MIDI THRU software mode.

Input buffer in the GSC-3/2 controller enables signal power gain (without voltage change) and it has impedance identical with a tube amp (1 Mohm).
When activating the buffer the guitar is loaded only by the guitar cable and by the buffer.
Comparing to the guitar the buffer has manifold bigger ‘power’ so the element after the buffer ( e.g. cable connecting GSC with the amp or active effect) will have no influence on the guitar tone. Such influence normally occurs when the cable connecting the GSC with the amp is quite long (e.g. 6m) and when it has big parasitic capacitance (high tones will be attenuated). It would occur also when the first effect in the signal chain would have low input impedance (if you don’t use the buffer your guitar tone will change).
However some guitar effects will sound better when the buffer is turned off. It is recommended to check if the given effect sounds better with or without the buffer.

In order to build the guitar systems without the hum you have to know how the ground loop arises and when it will be the ‘hum’ cause. ‘Hum’ is the sound which occurs after amplification of the voltage induced in cables by the disturbing electromagnetic field. Disturbing EMF is generated near to supply transformers, and sometimes even near to supply cables with the flow of big current (e.g. 50A). The bigger the transformer power (and its size and weight) the bigger the disturbing field.
Fortunately intensity of this field drops considerably along with increasing the distance. For example the typical 100 Watt tube amp supply transformer mostly interferes in space up to 1 meter around itself but in 2 or 3 meter distance the field is almost completely omitted. It is easy to check it with the single coil pickups guitar.
But what is exactly the ground loop?
The ground loop is any fragment of our system in which the ground wires (signal or power cables) make the closed loop (in other words the coil).
If such a coil is enclosed by disturbing electromagnetic field there appears in it the current induced by that field. This current puts on the signal cable ground the voltage which generates audible hum. It is particularly heard when we use the high gain (overdrive channel). There is also another rule – the bigger ground loop size the bigger hum we hear.


How to avoid the ground loops?


Firstly, building the systems you have to do it avoiding appearance of the ground loops. Especially those which are related with the amp as an amp has always the supply transformer inside.
The best way is to draw your installation scheme to see at once where the ground loops are.
You have to remember that inside of some devices there are used the isolating elements in order to avoid the potential ground loop. For example every of MIDI connections is not the galvanic one because just after the MIDI IN connector there is an opto-isolator which provides the isolation. Similarly to the relay type outputs (SWITCH OUTPUT) in the controllers (e.g. G Lab GSC) where the isolation is provided by the electro mechanic relay. More complicated is situation with the multioutputs power supplies for guitar effects even though many of the producers indicate exactly where the isolation occurs (e.g. G LAB PB-1). In many devices there are the switches named GROUND SELECTOR or GROUND LIFT that serve to eliminate the ground loops and are also necessary because lack of the connection with the ground makes also the hum problem. You have to remember also that ground loops appear also due to the supply cables containing protective wire (Protective Earth named „grounding”). Guitar tube amps posses a connection between signal ground and protective wire which you have to remember about. That’s why connecting the guitar simultaneously to two amps by regular A/B/Y switcher creates the ground loop and hum.


Please notice that not every ground loop makes the ‘hum’ herable. If it is small size (e.g. between the devices in pedal board) and there are no bigger transformers (>10W) in pedal board and around it, you will not hear that a ground loop exists even on the high-gain.


If we use an amp and stompboxes the ground loop arise mostly from connecting to common supply the effects placed between the guitar and an amp input and the effects connected to the amp effect loop.


You have to pay attention with preamps and other devices (rack effectors), which features a power supply with ground (PE connector). If the PE wire is connected with signal ground (as it is in many preamps) and our amp or power amp also has a connection between PE wire and signal ground there will appear a ground loop (more or less hearable). Good solution in such case is to use low resistance (of shield ground) signal cable.


An example of a ground loop which appearance is not always hearable is connecting to the amp FX loop the effect. You will not hear the hum of the ground loop with high signal level on the loop (it is not always so) and which signal (SEND and RETURN) cables connected to the effects are placed as near as possible one to another (the best way is to stick them every 20 cm with plastic band clip on the final stretch near the amp).


Basic rules of building the guitar system: the effects system situated between the guitar and the amp input from the system with the effects connected to the effect loop (there shouldn’t be connection between them e.g. by the power supply or looper),
2.the connection of earth with the signal ground should be only in one device (usually in the amp). In some devices e.g. power supplies or “bigger” effects the supplying wire has the protective contact but mostly it isn’t connected or connected thru the resistor (from 10 to 50 ohm) with signal ground, use the effect power supplies with isolated outputs to supply the particular effects, supply from the same voltage source (if necessary) only the effects and other system elements that are in the same fragment of the system (e.g. on the effect loop), keep the distance between or to isolate the metal cases of the JACK connectors to prevent from the accidental connection with other ground – especially that from footswitches and amps controlling signals.

The example of setting G Major as a MIDI 1 device on the channel no. 1,
choosing presets from user bank.


1. Press G Major MIDI/UTIL button and set:

MIDI Chan 1 – MIIDI channel no. 1

MIDI PrgCh On – receiving Program Change type commands

Prg Bank User – choosing presets from the user bank


2. Using the MIDI cable connect GSC MIDI OUT output with G Major MIDI IN input.


3. Check if the transmission channel in GSC controller is set to no.1 for the MIDI 1 device.


4. For individual presets it is needed to program certain numbers which are sending to MIDI 1 device.

Typical problem of many guitars equipped with humbackers is too high level of bass from a neck pickup comparing with a bridge pickup. If a guitar is connected to DVO or GSC (or any other device with the input impedance 1 MΏ) it is recommended to correct this guitar electronic circuit according to the diagram below. Bass correction is maintained by the additional C3 capacitor. Its capacitance have to be adjusted to the required cut bass level (e.g. from 2.2 nF to 4.7 nF). On the diagram below, comparing with a typical circuit, there are also corrected capacitances of C1 and C2 (defining the range of treble adjustment) from the value 22 nF to 2.2 nF or 4.7 nF.


Many guitars (with two volume pots) are equipped with an electronic circuit enabling them to mix in any proportion signals from pickups (even lowering to zero the volume of one of the pickup do not mute the guitar). Such a circuit cuts treble while the guitar volume is lowered (as much cut as longer is the guitar cable) and changes the guitar tone when its volume is reasonably lowered (the resistance of the pot „short circuit” the pickup). To solve this problem it is recommended to modify the circuit according to the diagram above. If after performing this step the effect of cutting treble still exists, then the reason can be long guitar cable (e.g. longer than 10 meters) or high parasitic capacitance of this cable (over 100 pF/meter).

An electric guitar is a source of very high impedance (from 75 kOhm to 150 kOhm) comparing to other devices like dynamic microphone or keyboard instrument (less than 1 kOhm). To not drive under or change the guitar signal, the guitar cable should have the lowest possible parasitic capacitance and the amp or other device connected to the guitar should have high input impedance. Typical tube amps’ input impedance is the level of 1 MOhm. Very often the guitar pedal effects’ input impedance is much lower and majority of them even switched off by their main switch still affect guitar signal. It can affect lower amplitude of the signal, change of the generated sound and noise generation or distortions. The influence depends on electronic circuits applied in the particular effect and the most reliable method to eliminate it is to skip effects not used currently. The idea of a effects loops switcher (looper) is coming from this need. Loopers can be grouped into 2 groups: simple (each loop has got its own switch) and programmable (for each switch are programmed effects loops which should be active). Programmable effects switches give possibility to quickly access to the programmed preset (pressing just one footswitch). The GSC offers dual mode of working: using presets footswitches can be selected programmed set of active effects and then used effects can be simply controlled.

Controlling all equipment by pressing just a button is required while live performances. Only such a solution gives possibility to play some songs (specially when there is just one guitar in use during a song). Lack of a solution to control the whole equipment by just one switch limits a guitar composer.
The GSC provides controlling possibilities similar to floor multi-effects but using regular devices (stomp boxes, amp) and more sophisticated ones (MIDI effects). Such a solution provides better sound quality and wider opportunities for a composer. The GSC in the beginning can be for many guitar players hardly to accept but after some experience they will find it as the best solution.

The guitar cable has got a parasitic capacitance. Capacitance depends on the length of cable and its structure. Even higher class cables have got at 6 meter length so big capacitance that it affects guitar signal (reduction of high frequencies).
This influence depends on “guitar electronics” (should not be considered for active “guitar electronics”) and is the most significant for guitars equipped with 500 kOhm volume control potentiometer. This influence depends on volume knob position (the biggest is in the medium position). For this reason the length of the guitar cable should be limited (suggested length is 3,5 to 4,0 meters). Very short (1,5 m) and higher class cable affects in significant boosting high frequencies.


Using the GSC enables to use short guitar cable (a cable 4 meters long allow to move inside a circle of 6 meters diameter in front of an amp).

The GSC enables to connect a mouth-organ microphone to an amp in switched mode: guitar or microphone (the guitar signal is automatically muted when the mouth-organ is in use and vice-versa).
To enable this connect mouth-organ microphone to one of the LOOP RETURN input and program a preset with this activated loop to which the microphone is connected.
The GSC enables to switch an amp (and eventual effects) to achieve required mouth-organ preset in a particular song.