1. Theoretical basics

  1. 1.1 What is voltage?
  2. 1.2 What is electricity?
  3. 1.3 What is the alternating current (AC) and direct current (DC)?
  4. 1.4 What is polarity and how to change it?
  5. 1.5 What is the power of a power supply unit?
  6. 1.6 What is the stabilization of voltage and current filtration?
  7. 1.7 What are ground loop and ground?
  8. 1.8 What is an isolated section?
  9. 1.9 When should an effect be isolated from others?
  10. 1.10 What is a toroidal transformer and how is it different from an ordinary one?
  11. 1.11 Why doesn’t YANKEE produce switched-mode power supplies?
  12. 1.12 What should be the distance between a power supply and effects?
  13. 1.13 What is the influence of the length and quality of the signal cable on the sound?
  14. 1.14 What kind of guitar effects are there?
  15. 1.15 What kinds of connectors are used with the effects?
  16. 1.16 What are the types of cables and adapters?

2. The design of YANKEE power supply units

  1. 2.1 Housing
  2. 2.2 The operating temperature of the device
  3. 2.3 The change of the position of the power socket
  4. 2.4 Outputs
  5. 2.5 Voltage change methods
  6. 2.6 Current-carrying capacity
  7. 2.7 Protections

3. The use of the Yankee power supply

  1. 3.1 How to affect the sound of the effect by changing the supply voltage?
  2. 3.2 Unwanted sounds – what generates them and how to get rid of them?
  3. 3.3 How to choose a power supply?


1. Theoretical basics

1.1 What is voltage?

Electric voltage, according to the definition, is the electric potential difference. The unit of voltage is the Volt [V]. The vast majority of guitar effects available on the market are powered by 9V voltage. Therefore, in accordance with the definition, the electric potential difference between the ground and the plus of the power supply is 9V. Each guitar effect should withstand a variation of +/– 10% in the supply voltage. Voltage variation can affect the sound, which is discussed in more detail below.

1.2 What is electricity?

Electricity, also known as the electric current, is defined as an orderly movement of electric charges. The Ampere [A] is the unit of the electric current. The milliampere unit [mA] is used to describe how many amperes are required for a particular effect, 1000mA = 1A. If one of the effects requires power consumption of 200mA and the other effect requires 0.2A, this means that both of these effects have the same power consumption.


Power consumption is slightly different from voltage consumption. Namely, the power supply must provide 200mA or more to power an effect that requires 200mA. There is no reason to be afraid that something wrong will happen if we connect a power supply with a capacity of up to 3000mA to the previously mentioned effect. The amount of electricity from the power supply will simply flow with the exact amount that is required by the effect, in other words 200mA.

1.3 What is the alternating current (AC) and direct current (DC)?

In addition to the values of the voltage given in [V] and the electric current given in [A], there is also an additional symbol of AC or DC. What does it stand for?

  1. AC (Alternating Current) – alternating voltage of a given value [V] and frequency [Hz] that changes its direction in a circuit
  2. DC (Direct Current) – constant voltage of a given value [V], of electric current flowing in only one direction

The fact that the voltage is constant (DC) means that it is the same in every time unit, it does not change.


Alternating voltage (AC), as the name itself suggests, changes and its waveform is sinusoidal. The changes occur at regular intervals with a given frequency. Let us assume that we have a 5.5/2.5 connector (section 1.11) and alternating current. In a given unit of time we have, e.g. + on the pin and – on the outside, then after a moment, as a result of the frequency, it is the other way around. Therefore, there is no concept of polarisation with alternating voltage. This is due to the regularity of changes in this voltage.

1.4 What is polarity and how to change it?

Polarity is a term which describes which part of the connector is connected to either “+” or “-”. Polarity reversal can be achieved by connecting an appropriate cable. Most guitar effects available on the market have the following designation:


This means that the potential, that is the positive supply, is on the outer part of the connector, whereas the ground potential supply is in the middle part of the connector. All Yankee power supplies have output polarity as described in the figure above. In the further part of this manual such polarity will be called “center negative”. In contrast, the kind of polarity, in which the positive supply is in the middle part of the connector (see figure below), and the ground potential supply is in the outer part of the connector can be called: center positive.


If polarity reversal is needed, use an appropriate adapter that changes polarity (section 1.16). After connecting the adapter, the polarity on the other end of the cable will be reversed.


NOTE! Polarity is a very important parameter! If we connect an effect using a connector whose polarity is different than the one required by the effect it will go up in smoke and the anticipated sound will be gone. Some producers may have anticipated such user errors and secured the effect against such connections. If that is the case, one needs to connect the effect with an appropriately polarized connector.

1.5 What is the power of a power supply unit?

The power of a PSU is the electric current value multiplied by the voltage value that the power supply unit can provide. Hence, if we have a 9V power supply, which has a current efficiency of 0.2A, then its power is 1.8W. The Watt [W] is the unit of power.


Frequently one question arises: Why is e.g. 1.8VA, instead of 1.8W, often written on equipment housing, if the unit of power is the Watt? Well, without going into details of electrical engineering, we can assume that 1.8VA is equal to 1.8W. Of course this is a simplification and we can adopt it when connecting guitar effects or any other devices, where the predominant component of the load characteristic is resistance.

1.6 What is the stabilization of voltage and current filtration?

A good power supply unit for guitar effects, in addition to having a voltage stabilizer, is also equipped with a voltage and current filtering system.


Stabilized power supply units have electronic systems, which “cut off” unwanted voltage so that the output voltage of the power supply is constant regardless of the connected device. In addition, electronic systems, stabilizing the supplied voltage, also “cut off” unwanted interferences, so that the effect works as intended. As a result, a stabilized power supply unit provides stable voltage under load, e.g. 9 V, whereas non-stabilized power supply units will gradually lower this value.


All Yankee power supplies are equipped with sophisticated voltage filtration and stabilization systems. Electric current filtering systems are intended to provide effects with the same current regardless of the present conditions in the power supply network. Theoretically, the power supply network, e.g. in Europe, is a sine waveform voltage of 230V and a frequency of 50 Hz. Unfortunately, the reality is that the shape of the mains voltage, and especially of the current, is rarely a sine wave, but looks like some “ragged” graph. This is due to the fact that there are many devices connected to the mains, which introduce interferences. It all has to be filtered so that the effects have the same sound in all conditions.


This raises a question: How did guitarists and sound engineers cope with such interference decades ago, when efficient filtering and stabilizing electronics was not available? Back then, there were fewer electric devices introducing interference than there are today. That is why nowadays it is very important to have a high-end power supply unit for guitar effects that can filter out all these interferences.

1.7 What are ground loop and ground?

For many guitarists the expression ground loop sounds very enigmatic. This term is very simple and there is nothing to be afraid of. I will try to explain this phenomenon using a few examples.


For instance, plugging one group of effects simultaneously between the guitar and the pick-up with another group of effects plugged between the preamplifier and the power amplifier, i.e. in the fx loop of our guitar amplifier. If we would like to connect all of the effects to a single power supply unit, which has the same ground on all outputs or using a daisy chain, then a ground loop may occur. In such case, there will be a potential difference because we do not have a single ground point. For the ground loop to occur, which generates interferences, there must be a source of voltage and a closed circuit. In this case the preamplifier will be a minimal, but a sufficient source, and the circuit will close itself via the signal ground and the ground of the effects. Thus, the minimum electric current will flow and this will cause audible distortions.


As already mentioned, for the ground loop to occur, which negatively affects the quality and clarity of the sound, two factors must be in place: a closed circuit from the ground and a minimal source of voltage. Therefore, if we have a ground loop, but in its circuit there is no source of voltage, then the loop will not negatively affect the sound and tone of the guitar. An example of this can be the connection of a few Boss analogue delays to one section of the PS-M1 power supply unit or on the basis of the daisy chain.

1.8 What is an isolated section?

While using power supply units, certain terms appear, such as: isolated power section, isolated output, etc. All of them usually mean the same thing. If we have 4 isolated sections in a PSU, it means the same as if we had four power supply units in a single housing, between which there is no current flow. Each isolated section is like a separate PSU.


Isolated sections provide a complete separation of electric charges flowing in a circuit. This is useful when, e.g. digital effects disrupt the current in the power supply, adversely affecting the sound of other effects in the same circuit. Usually this manifests itself in “humming” or in unwanted sounds. Such effects have to be separated from the others. In addition, any effect using alternating current (AC) must be isolated from others.


In the YANKEE Solid Series of power supply units some sections are divided up into a greater number of sockets, not separated from each other. This works similarly to a daisy chain, but the user may connect each effect with a separate cable. If a particular section has a maximum current carrying capacity of 1200mA, then the effects plugged into all sockets of a particular section must consume no more than 1200mA.

1.9 When should an effect be isolated from others?

There is no simple rule to determine whether an effect will generate interference when connected to a power supply section with other effects. There are some guidelines that will work in 90% of cases, but sometimes there are settings which will produce unwanted sounds contrary to the guidelines or, to everyone’s surprise, no sound at all. The only way to ensure that a given set does not produce interference is to test it in a good, traditional store.

Effects which must always be isolated:

    1. ▪ Effects connected between the guitar and the guitar amp, and the amp FX LOOP. These two sets must always be isolated from each other.


    1. ▪ In general, it can be assumed that all digital effects have to be on separate outputs. For safety reasons you can assume that all effects whose power consumption exceeds 300mA are digital effects.


    1. ▪ Tube effects – just like digital ones.


  1. ▪ All effects built with germanium transistors, such as Fuzz Face, i.e. those which have a positive supply on the signal ground. Each manufacturer of this type of effect states in the manual that it must not be connected to the common supply earth with other effects under any circumstances.


1.10 What is a toroidal transformer and how is it different from an ordinary one?

The basic element of a power supply unit is the transformer. It is an element lowering the mains voltage to a value suitable for electronic systems. By far the most commonly used transformers are classic ones, the so-called EI and toroidal transformers.


Yankee power supplies PS–9/700, PS–9/1000, PS–9/120 and PS–18/90 use classic transformers, whereas the other Yankee models use toroidal transformers. Toroidal transformers, on account of their construction, offer a more natural path for the magnetic field inside the core, hence the aforementioned field affects nearby devices to a lesser degree. If such a transformer is also made of good quality materials and placed in a metal housing, such as in red Yankee power supply units, then we can be sure that no stray electromagnetic field will adversely affect the sound of our effects.


In general, if the equipment is used at home, where amplifications are rather small and the power supply is further away from the effects, power supply units with classic transformers will be sufficient. But when the equipment is used during a concert or in a recording studio, then, in order to prevent unwanted hum and distortion of sound, one should use a power supply with a toroidal transformer in a metal housing.

1.11 Why doesn’t YANKEE produce switched-mode power supplies?

Why has Yankee decided firmly against switched-mode, also called switching-mode power supplies? In theory, switched-mode power supplies offer only advantages: high performance, small size, low price … and that’s it. But let us start from the beginning. What are switched-mode power supply units and why should they not be used to power professional effects?


The problem with switched-mode power supply results from their operation at a high frequency of electric energy transformation, often at several or over dozen kilohertz. It is exactly the working principle of a switched-mode power supply that causes audible squeals in the signal path. Sometimes, of course, switched-mode power supplies will work well, especially when playing at home and with low amplifications. However, if on a studio or a stage, then you will often hear a high frequency hum, especially when a single switched-mode power supply provides power to several effects.


Sometimes, in spite of everything, we can use switched-mode power supplies to power the effects. It is also true there might not be any interference even at high amplification. However, in these instances, the effects are not very demanding and consume little power. There is a huge number of ways in which we can connect together effects, guitars, amplifiers, drivers, and only a few percent of them will work with switched-mode power supplies. However, if we use a switched-mode power supply, and there is to be a change in the connection to our signal path, then we have a high risk of interference occurring.

1.12 What should be the distance between a power supply and effects?

If we have a high quality power supply equipped with a good quality toroidal transformer in a metal housing, then we can place effects next to the power supply and it will have no effect on the sound, nor will it generate interference in the signal path. On the other hand, if we have a poor quality power supply equipped with a standard transformer in a plastic housing without shielding, then, in order to avoid interference, we have to place the power supply as far as possible from the effects.

1.13 What is the influence of the length and quality of the signal cables on the sound?

Although this issue is not directly related to power supply units, it is, however, extremely important. We have bought a great amp, a good guitar, and dreamy effects, but it turns out that the sound of the guitar is fading or is very distorted (when all true bypass effects are turned off). We may suspect the power supply to be the culprit, but the source of the problem is in long and poor quality signal cables.


The length and quality of signal cables affects the guitar signal through “cropping up” and often through “collecting” interference from all the electromagnetic fields originating from various devices in our surroundings. Therefore, follow these rules: cables in your pedalboard are to be as short as possible, and have the lowest possible resistance and, even more importantly, the lowest possible capacitance.

1.14 What kind of guitar effects are there?

Effects available on the market can be divided into three types:

    1. ▪ Classic analogue – by far the largest group: small stompboxes using transistors and integrated circuits. They are not particularly demanding as far as power supply is concerned. They consume less than 100mA, and usually you can connect several of these effects to one section. The exceptions are, e.g. effects with germanium transistors or MOOG effects.


    1. ▪ Tube – as the name suggests these are effects that process sound using a vacuum tube; they are easy to recognize because manufacturers most frequently expose the tube. They have the highest power consumption of all the groups. They must always be connected to isolated outputs.


  1. ▪ Digital – effects that process signals using digital circuits. More and more popular are signal processors, which have high computing power, but also consume a lot of electricity. Examples of such effects are devices produced by such renowned companies like Strymon, Eventide, and TC Electronics. They must always be connected to isolated outputs with a high maximum current consumption – mostly up to 400mA.

Of course not all devices fall into this classification, but still most of the effects can be assigned to some of these groups.

1.15 What kinds of connectors are used with the effects?

The most commonly used connectors (with a few exceptions) are as follows.


    1. ▪ 5.5/2.1 connector – also called a standard or boss type, it is by far the most common power connector for effects. The number 5.5 is the external diameter in millimetres, whereas 2.1 mm means the inside diameter, that is, the diameter of the pin in the socket of the effect.


    1. ▪ 5.5/2.5 connector – connectors of this type are typically used with effects requiring alternating current or direct current and high power. On the surface, it looks very similar to a standard one, and differs only in the size of the internal plug, which is 2.5 mm. Yankee 5.5/2.5 connectors are made from white plastic.


    1. If our effect has a 5.5/2.5 socket, then it will not be possible to insert a 5.5/2.1 plug, because the inner pin of the socket will not fit in the hole. On the other hand, if our effect has a 5.5/2.1 socket, it is possible to insert a 5.5/2.5 plug into it. However, our effect may not work properly or not at all because the pin in the socket is 2.1 mm, and the hole in the plug is 2.5. The 0.4 mm does make a difference, however small it might seem.


    1. ▪ 3.5 mm mini jack connector – a connector with a 3.5 mm diameter. The effects are always powered with mono type connectors, not stereo. Polarity is not an issue in this kind of connectors because, if the power supply has a standard polarity (center negative), the positive supply is always at the tip of the plug – tip positive.


  1. ▪ 9V battery connector – very rarely there are effects, which do not have a power connector and are adapted to a 9V battery supply. Polarity is not an issue in this kind of connectors because, if the power supply has a standard polarity (center negative), the plus is always on round-shaped parts and minus on hexagon-shaped parts.

1.16 What are the types of cables and adapters?

The most commonly used cables and adapters (with a few exceptions) are the ones described below. A cable differs from an adapter in that there are two connectors in a cable, while there is one connector and one socket in an adapter. However, they work in the same way.


    1. ▪ Classic cable – a cable with a single connector at both ends, either 5.5/2.5 or 3.5/2.1. This cable does not reverse polarity.


    1. ▪ Mini jack cable/adapter – a cable/adapter with a 5.5/2.1 connector/socket at one end and a 3.5 mm mini-jack connector at the other. The tip of the mini jack is connected to the outer part of the 5.5/2.1 connector. This means that if a cable is connected to any DC output in which the polarity is center negative, then the tip of the mini jack will have positive supply (tip positive). Only such polarity is allowed in effects with a mini jack connection.


    1. ▪ 9V battery cable/adapter – a cable/adapter with a 5.5/2.1 type connector/socket at one end and a standard 9V battery connector at the other. If a cable is connected to any DC output in which the polarity is center negative, then the polarity of the plug is the same as in the battery.


    1. ▪ Adapter changing the size of the connector – an adapter with a 5.5/2.1 type socket at one end and a 5.5/2.5 type connector at the other.


    1. ▪ Adapter changing polarity – an adapter that reverses the polarity of the connection. If you have a power supply that has a center negative polarity, connecting the adapter at the outlet will reverse polarity to center positive. It has 5.5/2.1 type socket at one end and a 5.5/2.1 type connector at the other.


    1. ▪ Adapter changing the size of the connector and polarity – an adapter with a 5.5/2.1 type socket at one end and a 5.5/2.5 type connector at the other. This cable also changes the polarity of the connector.


    1. ▪ Adapter summing up the voltage – an adapter with three connectors, which sums up the voltage from two separated sections. If the two adjacent plugs are connected to isolated outputs, then on the third connector, which is away from them, the voltage is the sum of the voltage values of the sections to which the cable is connected.


    1. For example, if we have two separated outputs 2 x 9 V, and the effect requires 18 V, then we can connect two plugs of the cable to these outputs, thus obtaining 18V on the third plug.


    1. NOTE! This cable must not be used when the two sockets in the power supply are from the same section.


    1. ▪ Adapter summing up the current (amperage) – a cable with five connectors, which sums up the current from two separated sections. If the two adjacent connectors are connected to separated outputs with the same voltage, then on the other connectors the maximum current consumption will be the sum of the current consumption of the sections to which the cable has been connected.


    1. If we have two isolated 9V outputs and each of them can provide up to 250 mA, then we can connect the two plugs of the cable to these two outputs, thus obtaining 500mA on the other plugs. For this purpose, we may also use a daisy chain cable.


    1. NOTE! There is no sense in using this cable when the sockets on the power supply are from the same section.


  1. ▪ Daisy chain cable – a cable with a few 5.5/2.1 straight connectors, which are usually 30 cm apart. It is available in two configurations: five connectors + socket; five connectors without socket (these are included in PS-M0 power supplies). A daisy chain simply means connecting the power supply to many effects. If a daisy chain cable is connected to the section which can give a maximum of 400 mA, then the effects connected to the splitter cable cannot draw in total more current.


2. The design of Yankee Power Supply units

2.1 Housing

The Solid and Expert series of power supply units by Yankee are housed in an aluminium casing. As a result we provide adequate shielding of the electromagnetic field mentioned above, but also very good heat dissipation, low weight and excellent mechanical strength. All power supplies in metal housing have handles with 4 mm holes. The holes allow for screwing the power supply unit into the pedalboard.

2.2 The operating temperature of the device

In section 1.6 the filtration and stabilization of voltage has been described, and the “cut-off” of unwanted voltage causing interference was presented. All the ”cut“ interference has to dissipate somehow, and this outlet is heat. During normal operation of the power supply, when it is working at its full capacity, the temperature of the casing can rise even by 40°C. These are perfectly normal operating parameters, which do not affect the service life of the power supply. In such cases, a very large amount of unwanted voltage is ”cut off” and converted into heat, which, thanks to the aluminium casing, is efficiently dissipated.

2.3 The change of the position of the power socket

Yankee power supply units are the only devices on the market that allow changing the position of the power socket. This feature allows placing the power supply under the pedaltrain (this does not apply to PS-M2), directly by the wall of the pedalboard or under the shelf for the effects. Thanks to the movable power socket, Yankee power supplies can be mounted on all pedalboards. Moving a socket is very simple. Just unscrew the bolts holding the socket and the cap, unplug the cables from the sockets, exchange the positions of the socket and plug, and then plug the cables back in.


NOTE! For the safety of the user and device, this operation can only be performed by specialists. The manufacturer is not liable for malfunctions resulting from changing the position of the power socket.

2.4 Outputs

In the standard series of Yankee power supply units, the effects are connected directly to the connectors, which are permanently fixed to the power supply. In the other power supplies, the effects are connected with cables of various lengths and types.


There are basically three types of outputs: AC, DC and USB. The AC output socket is 5.5/2.5 type, whereas the DC output socket is 5.5/2.1 standard polarity – center negative. This difference was introduced so that users do not accidentally connect effects powered by DC voltage to the AC output. If we have an effect requiring 9V DC and we connect it to a 9V AC power supply output, most likely it will be destroyed. On the other hand, if we connect an effect requiring 9V AC to the 9V DC output, it won’t be damaged and it will simply not work until we connect it to its favourite 9V AC.


One should also note that Yankee power supplies feature isolated sockets and sockets with a common power supply ground. The difference between them has been described in Section 1.5. All DC sockets are normally polarized center negative, i.e. the plus is on the outer part of the plug.

2.5 Voltage change methods

DC voltage change in Yankee power supply units is achieved by:


    1. ▪ The DIP switch – the voltage change consists in flipping the switch to the desired position, as described on the power supply housing or in Quick Setup Manual.


    1. ▪ The single-turn potentiometer – the voltage change involves setting the potentiometer in the desired position. At the maximum deflection to the left – the output voltage will be 1V DC, with a maximum deflection to the right – the output voltage will be 10V DC.


  1. ▪ Multi-turn potentiometer – the voltage change involves turning clockwise to increase the voltage or counterclockwise to decrease. The set voltage is shown on the display at the top of the power supply case.


The AC voltage, in a given socket, is always constant. For example, in model PS-M2 in section 5 we have 3 sockets and each of them has a different AC voltage. The first has a voltage of 9V AC, the second has 12V AC, and the third has 14V AC. The voltage change in this case consists in plugging the cable into a different socket with a different value.


NOTE! Please note that in the sections with AC voltage, you can only use one socket at a time.

2.6 Current-carrying capacity

The current-carrying capacity is simply the maximum current that can flow from the power supply. On the red housings of Yankee power supplies, the maximum current value that can flow from a given output when it is set at 9V is shown. Dear guitarist, you should keep in mind that if you would like to use all outputs set at the max values, then the thermal protection will activate. The overall current that can flow from the power supply depends on voltage settings and can be calculated from the power of the PSU transformer.


2.7 Protections

Yankee Power Supplies from Solid Series and Expert Series are equipped with all possible protections, i.e.:


    1. ▪ Overvoltage protection in Yankee power supplies is in the form of a slow-blow fuse mounted in the housing of the mains power socket. This protection is also used to protect the power supply against an excessive overload. In a situation where there is too high voltage in the supply network threatening devices or the power supply is overloaded for a long time, then the fuse will blow and will need to be replaced. The replacement procedure is very simple. Unplug the power cord and using a screwdriver pry open the cap that covers the fuse. There is a nice surprise under the cap. We don’t need to at once run around shops and look for the appropriate fuse, since under the cap there is still one spare fuse. We can simply replace it and continue enjoying the sound of the set, and in our free time we can buy the fuse.


    1. ▪ Overcurrent protection will be activated when the current from a given output exceeds the rated value, i.e. the value for which the power supply was designed. If, for example, the Nova Delay effect, which requires 400mA output, is connected to an output which can provide only 100mA, then the protection will be activated in such a power supply output, and the effect simply will not work. Nothing will be damaged, you just need to connect the effect to another output with a higher current capacity.


    1. ▪ Thermal protection is intended to turn off the power supply when its temperature exceeds the acceptable value. A few paragraphs earlier, the aspect of the power supply being heated up has been discussed. Here it should be noted that this is inevitable and the heat has to escape somewhere. If the power supply was tightly covered with no ventilation and at the same time loaded with power consuming effects, then there is a risk that it will turn off until the temperature lowers. In this case, you should uncover the power supply, allow air access, and it will be ok.


    1. ▪ Short-circuit protection will be activated if, for some reason, e.g. accidental inserting a screwdriver into one of the outputs, there will be a short-circuit in the socket, or one of the effect’s powering cables will have a short-circuit. The protection will work until you remove the short-circuit.


  1. ▪ Simultaneous AC/DC connection protection is installed in Yankee power supplies, in which there are sections where you can choose a socket with AC or DC. It is needed when by accident an effect using DC voltage is connected to the same section with an AC socket for an effect using AC voltage. If they were to be connected with a signal cable, then certainly one of effects would be damaged. Yankee power supplies have such a protection, so even if effects are connected in this way (incompatible with the information on the housing), then one of them will stay silent and wait for its turn for power, but it will be fine.


3. The use of the Yankee power supply

3.1 How to affect the sound of the effect by changing the supply voltage?

At first glance, it may seem strange to affect the sound through the power supply. However, it is true, but not for all effects. Most analogue effects, especially those older ones, exhibit significant sound variations, if we change the supply voltage.


Surely as a guitarist you have experienced a different sound of the effect if the battery has discharged. In this case, the voltage decreased from, for example, 9V to 6V DC, then the effect is less dynamic and sounds different. The sound characteristic can also be changed by gently increasing the voltage. For example, if an effect is supplied with 9V, and we supply it with 10V, then we also get a different sound out of the effect. There are also analogue effects that have 9V – 18V DC supply voltage specified in the technical specification and they sound different on different supply voltages.


PS-M2 and HS-M10 power supplies are equipped with SAG outputs, thanks to which you can change the voltage smoothly from 1V to 10V DC.


In the HS-M12 and HS-M24 power supplies there is a possibility of continuous voltage adjustment between 1V to 24V DC. Looking at the display, we can keep track of the current voltage for each output.

3.2 Unwanted sounds – what generates them and how to get rid of them?

    1. ▪ Interferences associated with the ground loop (section 1.7).


    1. ▪ Interferences associated with a poor power supply (sections 1.6, 1.9, 1.10, 1.11).


    1. ▪ Interferences associated with low quality cables, both current and signal cables, unsuitable connectors or polarization. If, for example, we have effects that have a socket size of 5.5/2.1 and we use a 5.5/2.5 connector, then once in a while there may be heard popping and cracking sounds, or other interferences (sections 1.4, 1.13, 1.16).


    1. ▪ If we plug in effects with higher current consumption than the power supply can provide (sections 1.2, 2.6).


    1. ▪ If we have a power supply with a classic transformer in a plastic housing, then unwanted sounds may arise if the power supply is located too close to the effect or if other devices causing interferences in the mains are plugged to the same network. This is particularly important if you use the Wah Wah effect with electromagnetic excitation (sections 1.10, 1.11).


    1. ▪ If you perform on a big stage, where there are powerful lamps, then sometimes a hum can be heard. This is because lamps or other devices are often used that generate interferences in the mains, and this further causes an audible hum in the speakers. If we have a good quality power supply, it should suppress the interferences, but sometimes it happens that the power supply suppresses such interferences but they will appear in the amplifier, because it is connected to the same mains. Then, if it is possible, ask the technicians to connect the guitar to a different power supply phase (section 1.6).


    1. ▪ There are old effects on the market, or new ones styled after the old that use NPN transistors. In particular, the germanium effects with a characteristic sound. This construction has the positive supply voltage connected to the ground loop. This is why it must be categorically separated from other effects with a classical construction. Otherwise, at best, there will be a loud wheeze heard from the speaker – not the sound that you want to hear. In the worst case – we will destroy the effect. Each manufacturer of such effects states in the user manual that such an effect must absolutely not be connected to the common ground power supply with any different effect (sections 1.8, 1.9).


    1. ▪ Digital effects, tube effects and specific analogue effects, such as MOOG, connected together with classic blocks through a daisy chain will cause a hum. As a rule, digital effects and tube effects should be supplied from separate outputs (sections 1.8, 1.9, 1.14).


    1. ▪ If we have the situation where we connect a DC-powered effect pedal to the AC output, then, at best, we will hear a loud hum from the speaker. However, if the effect does not have any protection against such connection, then the effect will burn out. It’s easy to make a mistake because, for example, Whammy IV is powered by 9V AC, but Whammy V is powered by 9V DC. However, if an AC powered effect, e.g. 9V AC, was connected to the DC output, e.g. 9V DC, then such an effect pedal would not be damaged, even if there is no protection. It may not function 100% properly, but after connecting it to the appropriate voltage value will it function correctly.


    1. ▪ A cable (signal or current) that for some reason has been mechanically damaged may cause an intermittent loss of signal or interference will be heard in the speaker.


    1. ▪ Most of the connectors supplying effects are polarized, so that the positive supply is on the outside of the connector (center negative). On the other hand, effect pedals have a metal housing connected to the ground supply in 99% of cases. If somewhere in the pedalboard we have a loose power plug, it happens that the plug touches the housing of the effect. Then we have a temporary short circuit, which will also be heard in the speaker. Please note: Avoid loose plugs!


  1. ▪ FX loop + daisy chain. Both groups of effects must be separated from each other. If we connect the effects before the preamplifier together with those from the FX loop with a common daisy chain cable, then a hum will be heard (sections 1.7, 1.8).

3.3 How to choose a power supply?

    1. 1. We need to have a specific list of effects that we want to power.


    1. 2. For each effect, we need to find the following information:


      1. 2.1 What voltage is required by the effect? How many Volts, AC or DC? (sections 1.1, 1.3)


      1. 2.2 How many milliamps does the effect needs? (section 1.2)


      1. 2.3 What kind of a plug and polarization does it require? (sections 1.4, 1.15)


      1. 2.4 Does the effect need to be isolated from others? (sections 1.7, 1.8, 1.9)


  1. 3. We need to plan how to connect the effects to the power supply, paying attention to their technical specifications.


Today, you know how many effects you have, but in the future you will want to buy some other effects or you will want to have a more developed pedalboard. In this case, you should choose a larger power supply, with a larger reserve, especially when it comes to the number of outputs with different voltages. To avoid a situation, for example, that we buy a power supply that has only 9V outputs, and after some time we come to like the sound of a 15V effect, again we will have a problem.