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The ultimate Guitar Rig Building Guide Humfree wiring of guitar systems and avoiding other noises 1st Edition | Published on 20th May 2014

Prostage S.L. • Apdo 57 • ES-07560 Cala Millor [email protected] • www.prostage.eu

Table of Contents 1.

Introduction

3

2.

Noise

4

3.

Hum Caused by Ground Loops

6

3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11

Earth | Chassis | Cable Shield Star-shaped Wiring Triangle | Ring Wiring Two Amplifiers Isolating Transformers to Prevent Ground Loops Switched Grounds Ground Loops over Effect Loops 19-inch Racks: Ground Connection via the Rack Rail Wireless Receiver Potential | Potential Compensation Galvanic Isolation

6 6 7 7 8 9 10 12 12 13 13

4.

Hum by Interferences

14

4.1 4.2 4.3 4.4

Interferences via the Pickups | Environment Interferences from Nearby Power Supplies | Transformers Interference by Parallel Cable Runs Interference over the Local Power Grid

14 14 14 14

5.

Hum Caused by Faulty Equipment

16

5.1 5.2 5.3

Missing Shield | Missing Ground Faulty Power Supply Faulty Tubes

16 16 16

6.

Other Noise Types

17

6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8

Hiss Whistling Sound | Switching Mode Power Supplies Scratching Transparency | Volume Loss Clicking | Popping Noise Clinking | Ringing, Combined with Some Kind of Feedback (Microphony) Crackling | Sizzle Rising and Falling Sound

17 17 17 18 18 18 19 19

7.

Important to Know

20

7.1 7.2 7.3 7.4 7.5 7.6

Impedance Capacity Balanced Signals (Microphone Cables) The Pseudo-Balanced Trick Serial | Parallel Effects Loops Latency

20 20 21 21 22 22

8.

My Dream Guitar Rig

23

8.1 8.2 8.3

The Order of the Effects Typical Configuration of the "Dream Guitar Rig" All You Need to Consider Building a Guitar Rack

23 24 26

9.

Trouble Shooting

29

9.1 9.2 9.3

Help! It's Buzzing - What to Do Important Warnings Step by Step Instructions for Trouble Shooting

29 29 30

10.

A Few Words About Prostage and the Author of this Guitar Rig Building Guide

32 Page 2

1.

Introduction

Dear guitarist, guitar technician, Prostage customer Big refrigerator sized racks were absolutely “in style” in the 80's. Nowadays, pedalboards are most popular. But a rack still offers many advantages over a pedalboard: • Greater reliability: the devices are protected from flying beer cans and water bottles. Furthermore, no one can stumble over the connectors or devices. • Better sound quality: You have less sound losses due to shorter cable runs. • Stompboxes can be installed in the rack. If you’re using the Prostage XDS loop system or a self-built drawer, you have convenient access to the effects in the open drawer during the show. You don't need to kneel in front of your audience to adjust something. Also, WahWah and volume pedals can be controlled remotely. You can find more information about this on the last page. • Faster set-up before the gig, because the rack-system is wired ready for use and - apart from the speaker cables you only have to run a single MIDI cable to the front of the stage. Professional bands that tour a lot therefore continue to rely on rack systems. The “Ultimate Guitar Rig Building Guide“ will help you build your system free from noise. Building a guitar rig free of hum and properly wired is not easy. Hum can have many different causes. Therefore, it is important to know the causes and solutions. Many statements are applicable, of course, also on guitar rigs that do not use a rack. The information is kept largely unbiased of products and will explain the system structure in general. This guide is divided into two parts: In the "theoretical part" (chapters 2-7) you’ll learn how hum and other noise occur and what is their cause. This knowledge is important in order to understand and implement the approaches described in the "practical part" (chapter 8 & 9). Part of the theory is a bit technical due to the nature of the subject. It is not imperative that you understand the technical details 100 %. But you have to know and understand the consequences that arise from the facts. We are sure that this extensive guide will save you some headaches in your rig building adventure. If you, nevertheless, cannot solve your problem, please write us an email to [email protected]. We will be glad to help you.

Page 3

--- Theoretical Part --2. Noise Where there is electricity, there is also noise. This is a physical fact and cannot be wiped out even with the best guide. If there is no noise, there is no power too. Our aim is to keep this noise as low as possible, ideally below the hearing threshold. There are three key factors: • Arrangement, placement of each device • Correct wiring of the guitar system • Quality of the equipment used, respectively the components used As your guitar signal passes from the pickup all the way to the speakers, there are many places where it can capture hum and noise. The closer this happens to the guitar in the overall signal path, the worse it will be, because the noise will be further amplified by each following device. Thus, the effect units and cables in front of the guitar amp play a more important role than those in the send / return. The following diagram illustrates this:

Loudness

Preamp

Poweramp

ita

Gu

l

na

g r si

mp

e

eb

m

Hu

/

eA for

is No

p

oo

Send

Return

e

ois

m

Hu Gain

/N

m fro

sL ect

Eff

Volume

Page 4

Particular attention in this context is given to distortion pedals. The distortion which we all love is produced by a component (e.g. the tube) when it is overdriven. Therefore it is driven into saturation. The component should actually amplify louder than it can effectively do. Therefore, the signal will now not get any louder, but the peaks are cut off. The higher the gain, the stronger the component is overdriven, the stronger the signal peaks are clipped and the greater is the distortion. The distortion therefore comes along with a compression effect. Quiet signal components, for example our noise, are further amplified because they do not reach the limit of the component. Therefore, with increasing gain the noise is coming closer to the actual guitar signal. In the extreme case, both signals are even identically loud! Gain Saturation (Distortion)

i

Gu

al

gn

si tar

e

ois

m

Hu

/N

Output Volume

Page 5

3.

Hum Caused by Ground Loops

Ground loops are certainly the most common reasons responsible for the hum. To understand and to get rid of ground loops, it is important to distinguish between "earth", "chassis" and "cable shield". But in a way, "earth", "chassis" and "cable shield" are the same, because they are somehow connected. And the term "Somehow" is exactly the problem. To avoid ground loops, we need to know where "earth", "chassis" and "cable shield" are connected. When wiring a guitar rig we must be aware where we want them to merge. This is due to the "potential" or the "potential compensation". The explanation comes at the end of this chapter. First we will take a look on how ground loops are created at all. 3.1 Earth | Chassis | Cable Shield Earth: (also called "ground"): The earth is, as the name suggests, the connection to the earth. This is the zero potential. In power cables, the connection to earth is called "grounding conductor". Chassis: If the chassis (housing) of a device is made of metal and the device is operated with mains voltage (120 / 240V), the housing must be grounded (connected to earth inside the device) for safety reasons. Cable shield: The shield is used to keep electromagnetic fields from the audio signal. Within guitar cables, this is the outer, mostly braided conductor. In order that the cable shield can fulfill its function, it must be connected on one (!) end to earth. In guitar cables, the shield is also used for the negative pole (unbalanced signal). Therefore, the shield must always be connected at both ends. With microphone cables (balanced signal), the shield can be connected on one side only under certain circumstances. For more details, please refer to chapter 7.3 Conclusion: Earth, Chassis and Cable Shield are always connected somewhere. To prevent hum by ground loops, it is important to know where they are connected. 3.2 Star-shaped Wiring Basically, the connection of "Earth", "Chassis" and "Cable Shield" must be structured like a star:

Instrument

Cable shield

Chassis

Chassis Chassis Central / common ground point (Zero-potential )

Earth

Page 6

3.3 Triangle | Ring Wiring If the star-shaped structure is not strictly observed and instead wiring is made in a triangle, the classic Ground Loop occurs. The problem is that the instrument is connected via two different paths to ground and the current can therefore flow through two different ways, respectively, the current can flow in a circle.

Instrument

Cable shield

Cable shield

Chassis

Chassis Central / common ground point (Zero-potential )

Earth 3.4 Two Amplifiers A typical example of such a triangle wiring is the use of two amplifiers. The following diagram shows a typical ground loop:

Page 7

Explanation of the Diagram on the Previous Page: In a guitar amp, the earth from the power cable and the shield of the guitar cable are connected to the chassis. In our example, the shield of the guitar cable therefore is connected to ground once thru the amplifier on the left and once thru the amplifier on the right. It does not matter whether the guitar signal is split by a Y-cable, or if the second amplifier is connected to the first amplifier. Due to the cable resistances, the potential for the two amplifiers are quite minimally different (we are talking about milivolts). Therefore, along the line marked in red, a small current begins to flow in the circle. This is the Ground Loop! The detailed explanation can be found in chapter 3.10. The Ground Loop is audible as hum because this current flows with the mains frequency (50Hz in Europe, 60Hz in America). In addition, the harmonics (100 Hz, 150 Hz, 200 Hz, .... respectively 120 Hz, 180 Hz, 240 Hz, .... ) are also generated. 3.5 Isolating Transformers to Prevent Ground Loops In order to prevent the ground loop, the connection of the cable shield from one to the other amplifier must be separated with an isolating transformer. Inside an isolating transformer, there is no electric connection between input and output. The signal is transmitted magnetically instead. Transformers specifically made for guitars must be used (e.g. Lehle P-Split) so that the guitar signal is transmitted unaltered. Isolating transformers for studio applications are not suited for guitars (see chapter 7.1 impedance).

Iso

IMPORTANT: Never cut the ground from the amplifiers power cord! Indeed this can solve the ground loop problem, but it is dangerous to life! Page 8

3.6 Switched Grounds If only one or the other amplifier shall be used at the same time, you can switch between the two amplifiers using an A/B switcher. There are A/B switchers that do not only switch the guitar signal, but also the shield / ground. Using such a switch, the triangle (ring) connection is suspended. This means, the ground of the guitar is connected either to amplifier A or B, but never to both. This also allows to suppress the hum. The disadvantage of this solution is that when switching the ground, the potential of the guitar is moved, which usually leads to unsightly switching noise (clicking). "Moving across" the potential is definitely not a neat solution and I would recommend to not do it whenever possible. In very complex guitar rigs, it may possibly be unavoidable in certain cases to switch the ground too. But I would never use a looper which switches the ground by default. More information about potential can be found in chapter 3.10.

Page 9

3.7 Ground Loops over Effect Loops A typical case for ground loops is also when inserting effects in the send / return of the amplifier and the whole is connected to the pedalboard with long cables.

Send Return

Page 10

The very strong hum you catch, when you use some effects before the amp and some in the effects loop (Send/ Return) of the amplifier and they are fed with the same, galvanically not isolated power supply or if the ground of the pedals otherwise are connected together, e.g. by jack plugs that touch each other. Effects before the amplifier and those in the effects loop must not have a common ground connection and must always be fed separately!

PSU

*

*

Send Return

* Note: The use of power distribution cables (special cables for simultaneous powering of several stompboxes) already creates a ground loop between the individual effect pedals. Since the cable run and therefore the circuit in which the current can flow are very short, there is no significant potential difference and no audible hum will occur. Therefore, this ground loops can usually be ignored. In certain cases, however, this very short loop may lead to problems.

Page 11

3.8 19-inch Racks: Ground Connection via the Rack Rail Within 19-inch racks you have to keep in mind that the chassis of the individual devices are connected together via the rail and therefore a ground connection is formed. Even if a 19-inch device does not have a grounding plug (or if it is pinched off), the chassis is still connected to the other devices via the rail. If the audio ground is connected to the chassis inside the unit, we have again a hidden potentially source of the hum. Since the housings usually are painted, it may even happen that the device did not have real contact with the rack rail yesterday. But ​​today, after transport (vibration), it has. Yesterday, everything was fine but today there's hum. Therefore, proper building of a humfree guitar rig already begins by bolting in the units! To fit a device isolated from the rack rail and therefore isolated from the other devices in the rack, one can use socalled "Humfrees". These are special, isolated rack screws with plastic washers. Important when using Humfrees is, that the housing is additionally isolated from the devices above and below using plastic spacers or stable plastic film. Especially protruding screws are otherwise again a source of error. Therefore, the unit must be mounted so that its chassis does not make contact anywhere to any another device or the rack rail. The isolated mounting serves its purpose only if the equipment is not grounded via the power cord. 3.9 Wireless Receiver Another ground loop trap are wireless receivers that have a metal housing or a 3-pin power plug. Unfortunately, within these devices, the audio ground (shield of the guitar cable) is usually connected to the chassis ex-works. The guitar cable is therefore connected to ground in front of the amplifier, and as a result there again is the dreaded triangle connection.

There are several solutions for this problem: • Professional devices have a ground lift switch, which allows you to interrupt the connection between the audio ground and the chassis/earth. In wireless receivers, that is rather not the case. But often, a cable can just be pinched off inside the unit, and the problem is solved. This should always be done by a trained technician. But sometimes, the devices are designed so that a separation of audio ground and chassis inside the unit is not very feasible. • If the receiver has a balanced output (XLR), you can apply the pseudo-symmetry trick (see chapter 7.4). • If the receiver does not offer the first two variants, you have to use an isolating transformer. • As a final alternative, you can mount the device with "Humfrees". See chapter 3.8. Page 12

3.10 Potential | Potential Compensation Why, however, is it humming when we wire devices in the triangle? Each cable has an electrical resistance, even if it's the best quality. This means that the voltage at the beginning of the cable does not completely arrive at the other end. This shifts the potential, or in other words: the potential at the end of the cable is no longer the same as at the beginning. The potential shifts slightly from the zero potential and differently in each and every cable. In two parallel routed cables, the potential shifts not just in parallel. The potential at the end of the cables are shifted against each other: Cable 1

Central / common ground point (Zero-Potential )

Potential shift Cable 2

Earth

Once the two ends of the cables are connected together again, a potential balancing occurs. Therefore, a small current starts to flow, which is driven by the mains frequency. Here it is, the hum! What we hear is the basic frequency of the power grid (50Hz in Europe, 60 Hz in America) and their harmonics with progressively reduced volume. Cable 1

Central / common ground point (Zero-Potential )

Cable 2

Earth

Important: The longer the power cords and guitar cables are, the greater is the potential difference and the greater is the hum. On very short cables, typically in a rack's internal wiring, this potential shift can be usually ignored. A guitar rack with very short cables can be seen as a large ground node with a single potential. But for all the cables leading out from the rack, the potential shift must be taken into account. 3.11 Galvanic Isolation Galvanic separation means that an electric signal is transmitted without electric contacts. This is done with transformers. The signal is transmitted magnetically. The ground line at the entrance of the transformer may have a different potential than the ground line at the output of the transformer. The two ground lines are not directly connected. Using a transformer, a floating (galvanically isolated) transmission is possible. In our guitar rack, galvanic isolation is used in two locations: • As a transmission transformer for audio signals to suppress ground loops (e.g. Lehle P- Split). • Within power supplies with multiple outlets for effect pedals. With these devices, you should always make sure that the outputs are isolated. An isolated power supply or a power supply with isolated outputs means that the outputs are galvanically isolated. Each output has a separate winding on the transformer and its own voltage regulation and filtering. In addition, these power supplies should have a toroidal transformer (explanation in chapter 4.2). These devices are, of course, more expensive than a simple power supply with multiple parallel output jacks. With such a power supply, it is also possible to simultaneously supply effect units in front of the amp and those in the effect loop of the amplifier.

Page 13

4.

Hum by Interferences

Hum can also be introduced by Interferences. Lighting systems, power transformers, computer monitors, fluorescent lights, electromagnetic interference from the building wiring, nearby high-voltage lines and many other sources emit electromagnetic fields, which we can capture with our guitar rig in different ways. 4.1 Interferences via the Pickups | Environment Pickups, especially single-coils, are very sensitive and act as antennas for noise. This is especially a concern because the signal of the pickup will be 100 times, or even 1000 times, amplified afterwards. The electromagnetic interference fields are different at each position in the room. In the studio, you can search the position where the pickups captures the least amount of hum. Often it also helps if you just turn to one side a little bit. When moving around the room, you can find out relatively easy where the interference may have come from and then maybe place the interference source differently or simply switch it off when not in use. Particularly obvious sources of interference such as fluorescent lights should just be turned off (and replaced with a candle ;). Your own guitar amplifier is also a source that emits interference. This is explained in the next section. 4.2 Interferences from Nearby Power Supplies | Transformers Transformers, especially the large power transformers of guitar amps or tube amplifiers, emit strong magnetic fields. The electromagnetic interference field decreases with increasing distance from the transformer. Toroidal transformers have, based on their design, a much, much lower electromagnetic interference field than normal (square) transformers. Especially with power supplies for multiple stompboxes, it is highly recommended that you choose one with a toroidal transformer. Effect devices and other devices that are located near a transformer can capture the interference. Therefore we hear the mains frequency as hum. If you stand too close to the amp with your guitar, the pickups catch this magnetic interference field. Particularly sensitive, for example, is also the Prostage Remote WahWah, since it uses a Fasel coil for the effect. The Fasel coil acts as an antenna for this interference. Therefore, to minimize hum captured by transformers, the distance between the transformer and the device that captures the hum, must be increased. Furthermore, the interference of (square) power transformers have a direction. Therefore, it can often help, to just rotate the device that captures the hum by 90° in place. 4.3 Interference by Parallel Cable Runs Guitar cables should never run in parallel to power cables. Otherwise, the mains frequency from the power cable crosstalks to the guitar cable. An "All-In-One" multi-core cable with guitar and power cords from the rack to the front edge of the stage is generally a very bad idea. 4.4 Interference over the Local Power Grid Noise may come into the guitar rig via the local power grid. A typical problem are dimmers of lighting systems. Dimmers chop up the power so that only a portion of the voltage goes to the lamp and therefore it lightens less. This chopping of the voltage has an impact on the local power grid and can be noticeable in your amp with unpleasant noise. Nowadays also signals, for example, internet connections, are modulated over the mains voltage. In general, you will never get a "clean" power from the power grid. This problem can be alleviated by a line filter. There are power strips with a built-in mains filter available for 50 to 60 USD. Simple 1U rack power conditioners also work with such filters. A good quality power strip with a line filter does the same job as an expensive 1U 19-inch power conditioner will do.

Page 14

In addition to power conditioners with a simple line filter, there are also AC voltage regulators. These devices do more than a simple line filter. They use a large transformer which not only regulates voltage fluctuations, but also helps to filter high-frequency noises from the power grid.

Page 15

5.

Hum Caused by Faulty Equipment

It may also be that a device hums without any external influences. On the one hand, this may be because the grounding has not been correctly designed inside the device itself or the shield is missing at all. On the other hand, it my be due to a faulty or poorly designed power supply or a defective component. 5.1 Missing Shield | Missing Ground If the grounding is not installed correctly in a device or if the grounding is missing at all, the unit hums. For guitars, this happens a lot of times. Note that very few guitars are adequately shielded and properly grounded ex-works. Even expensive ones may lack this. If the noise actually gets louder when you touch the strings, it is likely that the strings are not well grounded or that the hot and ground wires to the jack are reversed. Make sure that the electronics are completely shielded inside the guitar, the strings are properly grounded and the jack connector is properly connected. The strings are grounded in general by the bridge which has to be connected to the ground. 5.2 Faulty Power Supply Devices that are operated with mains voltage, therefore alternating current (AC), must transform the voltage first and then rectify it. After rectification, the voltage needs to be regulated and filtered in order to get the clean DC voltage (DC) which the device requires. Now, if this filtering is not made properly (e.g. by the use of undersized or inappropriate, cheap components), part of the mains frequency (50 Hz in Europe / 60Hz in America) remains in place and the unit is buzzing. Particularly audio devices are very sensitive to dirty rectified power supplies. This filtering, or voltage smoothing, is realized with the so-called electrolytic capacitors. These components dry out over the years, therefore they are losing their effect. Therefore, especially old tube amplifiers tend to hum. The only solution is to exchange the old electrolytic capacitors, even if the amp therefore no longer is original. But it will sound better in any case. Have the unit serviced by a qualified technician. 5.3 Faulty Tubes Tubes wear out and must be replaced from time to time. Also a new tube can sometimes have a manufacturing defect and therefore is not working correctly. Tubes have a heating. The filaments are fed usually with alternating current, similar to an old, traditional light bulb. In a defective tube, the heating current can crosstalk to the audio signal. Power tubes need to be calibrated after the exchange. Have the amp serviced by a qualified technician. Some tube amplifiers have a hum compensation circuit, which is adjustable via a potentiometer. If this is the case, the hum can lead from a incorrectly adjusted or defective potentiometer.

Page 16

6.

Other Noise Types

6.1 Hiss Hiss noise results from the fact that in every electronic component some electrons whirl around uncontrolled. How strong the noise in a device is, depends on two factors: • The quality of the components used • The electrical design of the device, therefore how the components affect each othe If we connect two devices in our signal chain, the components of the two devices affect each other too. Consequently, the interaction of multiple devices has an effect on the hiss. Also, impedance plays a part (see chapter 7.1). When devices are connected together with unsuitable impedance, this increases the hiss noise. You can minimize the hiss by using only high-quality equipment. Whenever possible, avoid using devices which generate unacceptably loud hissing. Pay particular attention to devices which are placed in the signal chain before the distortion pedals. Under certain circumstances, a change in the effect order can reduce lot of the hiss. At least, put very noisy devices in the signal chain after the high-gain devices, such as distortion pedals. 6.2 Whistling Sound | Switching Mode Power Supplies Whistling sounds usually come from a so-called switch-mode power supply. These are power supplies that do not have a power transformer, but crop the current. This occurs at a high frequency, and this can result in an audible whistling. Switch-mode power supplies are suitable for audio applications to only a limited extent and only if they are high-quality power supplies with very good filtration. Stay away from cheap power supplies from the supermarket! Switch-mode power supplies can be recognized by their very lightweight and small construction. A typical example of such power supplies are cell phone chargers. In certain cases, however, these power supplies can also solve problems. Since they do not have a classical mains transformer, they also do not send out mains frequency interferences as described in chapter 4.2. If a normal power supply (wall wart) causes a hum, you can replace the power supply by a switch-mode power supply and the hum is gone. 6.3 Scratching Scratching when adjusting controls A scratching noise indicates that the pots are worn or dirty. In particular, high humidity is detrimental to the pots: The contact surfaces oxidize. A slight scratching can be usually eliminated with contact cleaner spray. Heavy scratching pots need to be replaced. In guitars and stompboxes you can possibly do it yourself. Amplifiers or other mains opperated devices must be serviced by a qualified technician. Scratching when moving an expression pedal You have connected your MIDI-capable guitar amplifier, a multi-effect device and a MIDI foot controller with expression pedal in a MIDI chain. Once you move the expression pedal with which you want to control an effect, you hear a scratching noise? This is because the MIDI commands crosstalks into the guitar signal. The expression pedal continuously transmits data as long as it is moved, that is, several hundred instructions per second. That's where the scratching comes from. Program Changes are not audible since only a single, very short command will be sent. Most likely, the MIDI signal crosstalks in the guitar amplifier. You can solve this problem by inserting a MIDI adapter in between, which filters out the commands from the expression pedal in front of the guitar amplifier (the amplifier requires only the program change commands). For example, the Prostage XTMpro adapter offers two independent MIDI Outs. You connect MIDI Out A to the guitar amplifier and adjust the MIDI True settings so that only Program Changes are sent to the amplifier. You connect the effect unit to MIDI Out B and send out all MIDI commands on this output. Page 17

6.4 Transparency | Volume Loss If you notice that your signal suddenly loses its transparency or volume when switching between different effects, it is most likely due to the different input impedance of the effects device you have switched to. More about "impedance" can be found in chapter 7.1. Transparency losses are also related to the capacity of the guitar cable. See chapter 7.2. 6.5 Clicking | Popping Noise Popping noises can arise from relays when switching amp channels or effect loops. Popping noises can also be caused by a discharging capacitor. Soft popping when switching pickups This usually happens only when there is a preamp in the guitar and is caused by a voltage building up in a capacitor somewhere in the circuit. A resistor from each terminal of the pickup selector-switch to ground can help. Another technique is to place very large resistors (approx. 470kOhm) between the switch terminals. But note that both options will alter your tone. Soft popping when touching strings or other metal parts on the guitar Through the contact of your body with the guitar, a capacitor is discharged. If there is an isolation capacitor between the signal ground and the bridge, you may need to place a 220k Ohm resistor across it. Loud popping when switching Loops A very soft popping noise when switching loops is normal. But if it pops very loudly, it is highly likely that there is a potential problem. This is also known as "DC-Offset". Because the device which is inserted or disconnected is on a different potential, the potential is compensated when switching, and this produces the pop. To avoid this problem, make sure that all units have a reference to the common ground point, even if the loop is turned off. Within loopers that switch the ground too, a separate ground connection must be established in certain cases. DC offset problems can also be solved with a capacitor in the signal path. There are ready-to-use adapters for this, such as the Lehle DC Filter. 6.6 Clinking | Ringing, Combined with Some Kind of Feedback (Microphony) A ringing sound going into feedback squeal too easily, can be caused either by the guitar or amp. Try the amp with different guitars to determine where the problem is coming from. Microphonic guitars Ringing may be caused by microphonic pickups, poorly mounted pickups or the tremolo springs. Make sure that the springs to adjust the pickup height and the tremolo springs can not resonate. The springs can e.g. be attenuated by a plastic hose slipped over the springs. Microphonic amplifiers Ringing in the amplifier is caused most probably by a microphonic tube. Usually, it is a preamp tube, but it can happen with power amp tubes too. This is fairly common with combo amps that have the tubes hanging behind the speaker. Tubes are electro-mechanical components, which absorb the mechanical vibrations and therefore give it to the audio signal. These vibrations are absorbed primarily by the vibrations of the housing. A microphonic tube can relatively easily be identified by tapping onto the chassis of the amplifier or softly knocking directly onto a tube. If a tube begins to be microphonic, this is usually a sign that it would soon fail completely.

Page 18

6.7 Crackling | Sizzle Crackling only when playing. Crackling while playing is due to static build-up on the pick guard. The charges are caused by your movement or friction between your body and the guitar. To counteract this, wear short sleeves or a shirt of a different material. Alternatively, cover the entire back of the pick guard with aluminum foil, which must be connected to the ground of the guitar. The guitar amplifier crackles even without a connected guitar If the amp crackles and sizzles on its own, it has a serious problem. Probably a tube will be failing soon, or the power supply breaks through. Turn off the power immediately and have the amp serviced by a qualified technician. Otherwise, more serious and expensive damage may result. 6.8 Rising and Falling Sound This noise sounds a bit like waves rolling onto a beach and also arises even if no guitar is connected to the amplifier. In general, only tube amplifiers are affected. This noise heralds a serious problem that is likely to get worse very quickly. Usually, it means that the tubes and/or the associated resistors are failing. Stop using the amp immediately and have it serviced by a qualified technician.

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7.

Important to Know

For successful wiring a guitar rack, a few other important aspects need to be considered: 7.1 Impedance The impedance describes the electrical resistance of an audio connection. The resistance at the input is called “input impedance”, the resistance at the output is called “output impedance”. If you connect your guitar to a stompbox, the guitar pickup has to drive the input of the stompbox. The lower the input impedance, the more the pickup must work, respectively, the stronger the pickup is loaded. Therefore, the guitar signal is attenuated and loses volume and transparency. For a high-quality signal transmission, the input impedance of the "signal consumer" (e.g. the stompbox) must be much higher compared to the output impedance of the signal supplier (e.g. the guitar). Since guitar pickups have a relatively high output impedance and deliver only a low signal, the input impedance on guitar amps must be very high. Usually it is 1 mega-ohm. In HiFi or studio equipment, the input impedance is much lower (the advantage of a lower impedance is that the device is less noisy). Hence, if a guitar is connected to a studio device, the signal is attenuated by the input impedance, which is too low. The guitar sound loses transparency. Unfortunately, there is no mandatory standard for the impedance within the bunch of stompboxes. Some devices are optimized for guitars (with a very high input impedance). Other effect units comply to the studio standards. And there are also units somewhere in between. But in general, ground effects are more suitable for use in front of the amplifier (high impedance), while 19-inch devices are usually inserted in the effects loop of the amplifier (low impedance). If several stompboxes are connected to a looper, the guitar might be routed once to a device with a high input impedance, and – in another loop configuration – the signal from the guitar encounters a low input impedance. Therefore, the signal loses volume and transparency as mentioned above. To solve this problem, the Prostage Booster | Impedance Matcher can be set between the guitar and the devices. The booster has a very high input impedance, optimized for guitars, and a very low output impedance. Therefore, stompboxes and studio effects devices can be connected to the booster. The impedance matching can be carried out in two places: • As the first device right after the guitar. The booster is, therefore, placed firmly in the signal path and works as a line driver | buffer amp. The impedance matching is for the subsequent effect device. When using a looper, this means that the impedance matching is for the first stompbox activated by a loop (chapter 3.8). • Directly in series before a certain stompbox with a too low input impedance. Like this, the booster is only in the signal path when the effect is switched on 7.2 Capacity Each electric component, particularly the guitar cable, has a capacity. The longer the cable is, the higher the capacity. The capacity is a resistance which depends on the frequency of the signal. The higher the frequency, the lower the resistance. In cables, the capacity is between the signal conductor and the shield, or ground respectively. Thus, the higher the frequency, the smaller the resistance between the signal conductor and the ground. As a consequence, the signal loses trebles. Therefore, it is extremely important that you use high-quality cables and that the cable runs are as short as possible. If you are looking for the perfect sound, you will not use a pedal board front edge of the stage, but connect your guitar directly to the amp using a cable as short as possible. Effect units are connected directly next to the amp or in the guitar rack with the shortest possible cables.

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7.3 Balanced Signals (Microphone Cables) Transmitting an electrical signal requires two wires. That is, the current flows between these two lines. In guitar cables, this are the inner lead (tip) and the outer wire mesh (shield). Therefore, the outer wire mesh serves at the same time as a shield as well as a signal conductor. Unbalanced (asymmetrical) signal:

In the balanced (symmetrical) signal transmission (microphone cable), the current flows between the two inner conductors. The outer wire mesh serves only as a shield. The audio signal is no longer hardwired to the shield and therefore is not connected to the ground. Thus the audio signal has no reference to ground and is therefore transmitted floating (potential-free). Balanced (symmetrical) signal:

If two devices that already have a reference to ground are connected with an XLR cable, the shield should be connected at one end only. Usually this is not done in the cable, but directly on the device itself (e.g. by a ground lift switch which disconnects pin 1 of the XLR socket). The balanced signal transmission has another important advantage. The signal is fed on the two lines in opposite phase. The input amplifier of the device that receives this symmetric signal then inverts the phase of the signal on pin 3 and mixes it with the one from pin 2. 2 3 1

If, now, a disturbing signal interferes into the XLR cable, it interferes equally on both lines. In the example below, e.g. upwards. The input amplifier now inverses the phase of the signal on pin 3. The interference signal is thereby inverted phase against to the interference signal on pin 2. When mixing the two signals, the noise on the two lines cancel each other. So, we can run much longer signal lines with XLR cables.

2 3 1

7.4 The Pseudo-Balanced Trick Basically, there is nothing against having balanced wiring on a guitar rig. However, balanced connectors are offered only in high-quality effects units, some wireless receivers and, perhaps, the one or the other modeling processor. But with a special cable, you can connect an unbalanced connector with a balanced connector, and therefore have a floating connection (without ground connection). This can save you a transmission transformer. 2 3 1

In this particular cable, the tip of the jack-plug is connected to pin 2 of the XLR connector. The ground (shield) is connected with pin 3 of the XLR connector. Pin 1 of the XLR connector is not (!) connected. IMPORTANT: If you connect an XLR input with such a cable, the signal loses 6 dB of its level. If you connect an XLR output this way, the signal is boosted by 6dB. Thus, give attention to correct levels and adjust the levels using the input and output gain controls on the device.

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7.5 Serial | Parallel Effects Loops In serial effects loops, the entire guitar signal is sent through the effect unit(s). The proportion between the original signal and the effect signal is mixed in the effect unit. A poor-quality effects unit affects the entire sound, including the unprocessed part (dry) . In parallel effects loops, the signal is split. On the one hand, the signal is sent to the effect unit via the effects send jack. But the signal is sent internally also directly to the power amplifier. By the Dry / Wet knob you can now adjust how much effects signal (wet) is added to the original signal (dry). The advantage of parallel effects loops is that the original signal reaches the final stage completely unaffected. If you want to insert several effects devices, it is also advisable to use a line mixer. With a simple line mixer such as the Lehle Parallel, an amp that only has a serial effects loop, can be supplemented with a parallel effects loop. It is very important for parallel effects loops that the effects unit sends back only the effect signal and no(!) original signal! Therefore, the effect mix must be programmed in the effects unit to 100% wet. Some effects units also offer a so-called "Kill Dry" feature that needs to be turned on when used in a parallel loop. If you don't do this, you have the original signal twice (once over the effects unit and once directly in the amp), which leads to unsightly comb filter artifacts when using digital effects devices due to their latency (see next section). 7.6 Latency Digital effect units (and also digital mixers) first convert the guitar signal from analog to digita. Then they have to think and calculate a little bit, and at the end, the signal is again converted from digital to analog. This takes a few milliseconds and the signal is delayed. This delay is known as latency. The latency is so short that you will not notice it while playing. However, if you mix a digitally processed signal with an unprocessed (analog) signal, a comb filter effect is formed, because these two, actually identical signals are slightly offset in time. Thereby, certain frequencies in the signal are boosted, others are canceled. The signal sounds therefore very unnatural, like a bad chorus.

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--- PRACTICAL PART --8.

My Dream Guitar Rig

8.1 The Order of the Effects The order the effects are connected is a matter of taste, but also has an influence on the noise and losses. The chart below should be understood as a starting point for the correct order. But it does not have to be done exactly the same way. In front of distortion pedals, only low-noise effects units should be used in any case. Therefore, it may also be useful to place the WahWah after the distortion. Effect loops in guitar amplifiers have very different level conditions and usually also other impedances as the input of the amplifier. Therefore you have to consider the following: • Stompboxes are basically designed for use in front of the amp and are only suitable in certain cases for use in the effects loop of the amplifier. Just try whether it sounds good or not. • 19-inches effect units without dedicated guitar input are not suitable for use in front of the amplifier and should always be used in the send / return.

Overdrive

Distortion

Compressor

Wah Wah

Buffer Line Driver

Fuzz

Send Return

Pitch Shift

Modulation

Reverb

Delay

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• A buffer or buffered bypass pedal (which buffers your signal even when the effect is turned off) at a strategic point in your signal chain can help maintain your core tone when running through lots of pedals and cables. A buffer at the beginning of your effects chain helps to compensate losses due to the long guitar cable and converts your guitar signal to a lower impedance which will enhance driving the following effects pedals. • Fuzz pedals want to be connected directly to the pickup of the guitar. Therefore, a fuzz has to be the first device in the signal chain, even before any Buffer | Line Driver. • Modulation effects can also be before the amp, depending on your taste. But Delay and Reverb should always come after the distortion. Therefore, if you are using the distortion of your amp, delay and reverb belong basically into the effects loop. • A volume pedal can be used in very different places, depending on its purpose. - At the very beginning of the chain, the pedal causes the same as the volume pot of your guitar. - In front of the return of the amp, it regulates the total volume in case of a serial loop, or the amount of effect in a parallel effects loop.

8.2 Typical Configuration of the "Dream Guitar Rig" The following design shows a typical example of the ultimate guitar rig. It is laid out as a Dry / Wet system. That is, on the left cabinet is the dry guitar signal which only contains the basic effects (WahWah and distortion). All other effects, especially reverb and delay, are only on the right (wet) cabinet. This is a very established principle. Further, the stompboxes are incorporated directly into the rack and are switched through a looper. The WahWah and the volume pedal / remote volume (VCA) are remotely controlled with expression pedals. Herein the cable run of the guitar signal is reduced to a minimum. The volume pedal (VCA) is used to control the overall level of the Wet cabinet in this example. The delay time of the multi-effect device can be taped with a switch on the foot controller, and the amount of effect is controlled with an expression pedal. Of course, the returns of the multi-effects could also be connected in stereo and distributed to two speakers. That would then be a wet-dry-wet system where the "Dry"-cabinet usually is placed in the middle.

foot controller X07

12 7 foot controller X10

to the Guitar Rig

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Foot Controller

Guitar Input Buffer | Line Driver

Remote WahWah midi

midi out A

in

ground

18V�DC 250mA

12V�DC 500mA

9V�DC 500mA

out B

9V�DC 500mA

out

return 4

send 4

return 3

send 3

return 2

in

out/thru

send 2

return 1

in

out

send 1

in

SAG

Prostage XDS Loop System

Input

Output

MIDI In

Muliti FX unit 1

Thru

Muliti FX unit 2

Input

Output

Splitter with isolated outputs

MIDI In

Thru

Remote Volume

(VCA)

midi in

Input

Send

Dry cabinet

in

out

Return

Line Mixer

Guitar Amplifier

out/thru

Input

Power Amp

Wet cabinet

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8.3 All You Need to Consider Building a Guitar Rack If you consistently implement the information in the theory section, chances are very high that your guitar rig is not buzzing. Here is a summary with additional hints on how to use all the theory in the practice: 1. Don't start building your rig three days before you go on tour. A guitar rig is something that takes a lot of planning up front and a lot of debugging before the rig is ready to go. 2. The arrangement of the units in the rack can play a crucial role. E.g. don't place sensitive analog effects units directly above the power amp. Above the amp, there should anyways be 1U be left blank to get more distance to the power transformer (to reduce the risk of interferences). For the other reason that the amplifier gets enough air and there is no heat build-up inside the rack. 3. If you're using a guitar head that you want to put directly on top of the rack, then use as the top unit in the rack something that is not sensitive to interferences, e.g. the rack drawer with your cables or the power distribution. 4. Before getting started with the wiring, you need to know where the central grounding point is, thus from where all the ground connections start from. This is usually the guitar amp, but it can also be the 19-inch rack (rack rail). 5. Before installing into the rack, check every 19-inch device by using an ohm meter, whether the audio ground is connected to the housing or the ground pin of the power plug respectively. The device which acts as the central grounding point (zero potential) for your rig must have the audio-ground connected to earth. Typically, this is the guitar amplifier or the preamp respectively. All other (peripheral) devices, e.g. effect units, should not have connected the audio ground to the chassis. Otherwise wiring this unit creates a ground loop. Some devices have a ground lift switch, with which you can determine whether the audio ground is connected to the chassis or not. If this is not the case, the connection can possibly be separated inside the device with few steps. Refer to a qualified technician. If a device does not let you separate the connection between audio ground and the chassis/earth, give these devices special attention when wiring your rig. Due to the short cable runs in the rack, usually no audible hum arises. But if the unit causes hum, you can find solutions to this problem in chapter 3.5, chapter 3.8 and chapter 7.4. A further solutions is described below in point no. 12. 6. If you want to install stompbox effects in a 19" drawer, use a drawer with a built-in looper. Otherwise, when using a separate, external looper, the cable runs are too long. 7. Basically, all power cords, switching and MIDI cables should be routed on one side of the rack, the audio cables on the opposite side of the rack. Run the power cords on the same side on which the majority of the equipment has the power connections. Do not install power cords and audio cables in parallel to each other. Where unavoidable, power and audio cables may cross in an angle of 90°. 8. All devices of your guitar rig must be connected to the same power source. Use a power distribution (power strip or 19-inch unit) with integrated line filter. (If units are fed by different power sources, signal routing must be balanced.) 9. The first unit after the guitar, which is supplied with main voltage, must always be grounded to earth!! Usually, this is the guitar amp, but it can also be an effects unit in front of the amp. 10. The structure of the ground connections (earth / chassis / cable shield) must always be star-shaped. 11. If a triangle cabling is unavoidable, this means a closed ring connection is build, then this ring has to be isolated with a transformer (e.g. Lehle P-Split). Alternatively, the signal may also be transmitted balanced, but without(!) ground connection. This means, Pin 1 of the XLR connection must be connected on one end only (This is ideally reached through the proper position of a ground lift switch on the device) 12. If a device already has a reference to the common ground point, e.g. over the rack rail or power cord, a hum may be avoided by custom jack cables where the shield is connected on one side only (ground lifted). Further, when a device is connected in the effects loop or using a stereo device, a hum may possibly be avoided by using only one cable with ground connected at both ends (e.g. input left). All other connectors of the device are wired using cables with single-ended ground. Here, you have to try a little to find what works best. Plug the grounded (normal) end of the cable consistently to the Output / Send, and the lifted cable end into the Input / Return. Warning: single-ended jack cables work only at very short cable runs. For long cable runs, they have the opposite effect. So be careful when using this cables, they may only be used very sparingly if really needed. Page 26

13. It is very important that you mark the lifted side of every cable, for example, by a colored heat shrink tubing or a different colored connector housing. Inside the rack it must be clearly visible at any times where grounds have been lifted. 14. The protective conductor of individual devices, so the grounding pin of the power cord, must not be lifted for safety reasons. Thus, always build your system in a way that no grounds must be lifted at mains cables.

Never disconnect the Earth off the guitar amp !! DANGER TO LIFE !! 15. You should test your rig after each component (looper, effects unit, mixer, etc.) connected to the signal path. If you add something and you suddenly are losing signal or you hear some hum, you know almost certainly that the last thing you added is the culprit. It is possible that the device itself is defective, or responds to interferences. But much more likely is that you have just wired a ground loop that needs to be fixed. 16. Well-known rig builders recommend unisonous Mogami cables and Neutrik or Switchcraft connectors. Soldered connectors are generally preferable to screwed or pressed connections. Test every cable before installation with an ohmmeter to make sure that the connections are good and there are no shorts. This applies to both, purchased and self-made cables. 17. Shorten the power cords as well as the audio cables exactly to the length that they must have. Do not wind long cables to coils. 18. Label the connectors on both ends of each cable. Once your rig is built, it will be difficult to trace a cable from one end to the other. If everything is labeled properly, it will be much easier to make changes later or to find an error. 19. Attach the cables to the rack so they do not fly around and the plugs can not fall out during transportation. 20. The ideal guitar rack does not send an audio signal to the front of the stage, but processes the signal completely in the rack. Due to the shorter cable runs, the sound gains in quality. Moreover, such a system is much more reliable. 21. You can fit your stompboxes in the rack, for example, using the Prostage XDS loop system. For the WahWah, consider the Prostage Remote WahWah or the Dunlop Rack Cry Baby. Therefore, you can remotely control your entire guitar rig using a MIDI foot controller and some expression pedals. 22. If the signal nevertheless has to be sent to the front edge of the stage, use a loop which is only active when the device on the front of the stage is actually used. 23. Pay attention that pedal power supplies with multiple outputs have galvanically isolated outputs and that they use a toroidal transformer. 24. Effects that are connected in parallel and mixed with the original signal using a Dry/Wet knob or via a line mixer must always be programmed so that they output only the effects signal. The unprocessed original signal must be muted on the effects unit output (kill dry). 25. The effects have to be leveled properly. This applies particularly to the 19-inch effect devices. They usually have an input and output control. 26. Final tip: Don't forget to always have a few spare cables with you.

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This is how a professional wired guitar rig looks from the rear:

Guitar Rig of Zach Petersen, Hot Licks Guitars Hawaii.

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9.

Trouble Shooting

9.1 Help! It's Buzzing - What to Do The fastest and easiest way to eliminate a hum is - to switch off the power! But that is certainly not the solution you are looking for. For trouble shooting, you need the following tools: • A jack plug with a 10k Ohm resistor soldered between tip and shield:

• An ohm meter: Once you have located the hum, you presumably need the ohm meter to test cables or to measure where the ground loop goes through. For example, you can check if the housing of the device is connected to the audio ground. How to test a cable: • If your ohmmeter has a dial to set the range, set it to the lowest range (usually 200 ohms) • Check the resistance from the tip of one end to the tip at the other end. It should read a couple of ohms or less, the closer to 0 ohms, the better. • Check the resistance from the sleeve (ground) of one end to the other. Once again, it should be nearly 0 ohms. • Set your meter’s range (if applicable) to the highest setting (usually 10M or 20M). Check the tip on one end to the ground on the same end. It should read as an open circuit (too high to measure). If the reading bounces around, the cable seems to have a to low impedance. This can be caused, among other things, by soldering the plugs too hot. • It’s very important when doing this test to not touch the metal parts of the test probes nor the cables themselves – that will throw off your readings. Also, don’t test on a conductive surface like a metal table! 9.2 >>> IMPORTANT WARNINGS Refer to chapter 4.1. If the noise level stayed about the same or even went up slightly, the problem is almost certainly not the guitar. 6. Unplug the other end of the cable from the amplifier (or from the device to which the guitar is connected to) and insert the 10k jack-plug into the input. If the noise level is significantly lower than the connected guitar, the problem is the guitar cable. Use only high-quality, undamaged guitar cables. The cable should not be longer than strictly necessary and not run next to power cables, transformers and other electromagnetic sources. If the noise does not significantly decreases, the cable is fine. 7. If the guitar signal is split, for example, with the use of two amplifiers, or in a dry / wet system, disconnect the second signal and test each signal-chain separately. Thus, if the hum is already resolved, you have wired the classic ground loop. Repeat chapters 3.3 to 3.5. 8. Disconnect the switching connection (e.g. amp channel switching) one after the other. If this eliminates the hum, a ground loop via the switching connectors exists. Ground loops through switching contacts can be avoided by the use of a switcher with isolated switching outputs. 9. If you are using effects before the amp, remove the effects or your pedalboard completely out of the signal path (Important: Also remove the power supply to the pedalboard!) and plug the 10k plug right into the amp input. If the noise level is much lower, the problem lies with the pedal board. Continue with the next step. Otherwise, skip to point 12. 10. Reconnect your pedal board and connect the 10k plug where the guitar usually is connected. If you use the effect loop of the amplifier, disconnect the cables from the send and return. If the hum is gone now, the problem is caused by a ground connection (ground loop) between the effects before the amp and those in the send/return. Usually these ground loops come through the power supply. => Refer to chapter 3.7. If the hum persists even without effects in the send/return, go to the next step. 11. Now, work your way all the way back to the amp by taking one device after the other out of the signal path while plugging the 10k jack always into the vacated input. Also disconnect the power supply of the effect. If the noise level drops significantly when you remove a certain device, this device or a combination of this device with one placed in front of it causes the problem. You can now temporarily power the pedal with a battery to see if the hum comes through the power supply. If you use a looper, plug the 10k jack into the input of the looper and connect the output directly to the amplifier. Remove all other devices connected to the looper (also switching outputs). If the problem still appears, the looper itself causes the problem. Otherwise it is due to one or more devices that are connected to the looper. Note that under some circumstances, this problem can also be caused by switching contacts (amp channel switching). Page 30

12. Remove the cables from the send & return of the effect loop of the amplifier. If the noise is gone now, the problem is with a device in the effect loop. If you have multiple devices looped, reconnect one after the other to the amplifier to find out which device is causing the problem. It is also quite possible that more than one device causes the hum, or that the hum is produced only by the combination of several devices in the effects loop (for example, when using a line mixer). 13. Disconnect one MIDI cable after the other from the MIDI In side. MIDI is basically a floating, and therefore hum-free, signal transmission. Unfortunately, not all manufacturers adhere to the standards. If the problem is solved by the removal of a MIDI cable, the MIDI In ​​jack of the corresponding device does not comply to MIDI standards. The device must be modified by a qualified technician: the connection to ground from the middle pin (No.2) of the 5-pin MIDI In connector must be disconnected. This connection must only exist on the MIDI Out / Thru, but never at the MIDI In. If the "bad" MIDI In ​​jack also runs phantom power for the foot controller, the problem must not necessarily be the ground connection of Pin 2, but it may also be due to the phantom power. 14. If the "naked" amp already hums, that is, the 10k plug is plugged into the input of the amplifier, nothing is plugged to the effects loop of the amplifier and no foot switch nor MIDI cables are plugged in, then the problem is the amp itself. Certain components of the amplifier wear. Especially tube amplifiers must be serviced regularly and the tubes have to be replaced from time to time. In very old devices, also electrolytic capacitors may need to be replaced. Have the device serviced by a qualified technician.

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10. A Few Words About Prostage and the Author of this Guitar Rig Building Guide You want a guitar rig with the ultimate sound. We support you in this! Our aim is to ensure loss-free signal processing and to provide absolutely reliable and road-ready systems. How are we doing this? In a Prostage system the guitar signal is processed completely inside the rack. Thus, there are only remote control units at the front of the stage. Realtime effects, such as the pure analog Remote WahWah, are controlled with an expression pedal. You switch your amp channels and stompboxes using a MIDI foot controller. The effects themselves are fitted in the XDS Loop System. This is a 19-inch drawer with an integrated true bypass looper and six isolated power supplies for guitar effects. In the rack, the effects are protected from flying beer cans or clumsy singers. Further, sound and dynamic losses due to long guitar cable runs belong to the past! The Prostage MIDI Foot Controller and Looper | Switcher are interconnected via StageWire. StageWire was developed by Prostage specifically for stage use. This stage-prove MIDI connection provides bidirectional communication of multiple devices via just one standard microphone cable from device to device. Further, StageWire also includes phantom power for the foot controllers. The Prostage devices are programmed very comfortably using the System Manager software for Mac and PC. About Prostage Prostage was founded in 2001 by me, Lukas Truninger. I am an experienced audio engineer and backliner from Switzerland. Beginning in my teenage years, I was increasingly interested in audio electronics and tuned tube amps. After completing my apprenticeship as a mechanic, I studied audio engineering at the SAE Institute. I have worked with several international touring bands, such as Krokus or the Pepe Lienhard Orchestra (Udo Jürgens), during the 1990s and early 2000s. In 2008, I moved the production to the EU, specifically to Spain. Here, the Prostage products are further developed and still handcrafted with Swiss thoroughness. My experience has now contributed to many construction details of the Prostage devices. Today, Wolf Hoffmann from "Accept" and "Flyleaf"'s Jared Hardmann are only two of many guitarists successfully using Prostage products on their extended tours.

Lukas Truninger Prostage SL

© 2014 Lukas Truninger, Prostage SL Page 32