If you’ve ever asked about some vintage pedals, you’ve probably heard about positive ground, plugging the pedal first after the guitar, or using batteries only. In this article, we’ll explain where these rules come from, and how to get the optimal use out of a vintage effect pedal.
vintage pedal power supply and positive ground
what is positive ground?
The first effects pedals were introduced in the 60s. At that time, germanium was widely used for the manufacture of transistors, before the use of silicon which has many additional advantages. So, the first pedal circuits were built with germanium transistors. These transistors were easier to produce in PNP format, i.e. operating with a negative current on their base.
NPN and PNP transistors.
One of the specificities of PNP transistors is that they need a negative supply to obtain this negative current. The idea is to consider as reference voltage the positive terminal of the power supply in the whole circuit, and to consider that the negative terminal is therefore a negative voltage of -9V.
Original Rangemaster with germanium PNP transistor, and modified version with a silicon NPN transistor. Source: Electrosmash.
It doesn’t seem intuitive, but what you need to understand is that a voltage always needs to be expressed with a reference. In a 9V battery, saying that the (+) terminal is 9V doesn’t make sense. The correct formulation would be to say that the (+) terminal is 9V higher than the (-) terminal. We can therefore consider that the (+) terminal is our reference (0V), and in this case, the (-) terminal is 9V below, so -9V.
Basically, in the first circuit, the battery is connected in the opposite direction to the second circuit. Each pedal has its own battery, so they are isolated from each other, allowing each pedal to have its own reference.
The battery on the left is referenced to its (-) terminal. This results in +9V on its (+) terminal. The battery on the right is referenced to its (+) terminal. So we get -9V on its (-) terminal. Connecting a positive ground pedal with a negative ground pedal means connecting the two batteries as in the diagram above, each pedal having its own reference.
the problem of positive ground with power supplies
The problems due to positive ground started to appear with the emergence of power supplies for pedals, especially daisy chains. These power supplies allow to power several pedals from a single voltage source.
As you can see from the two schematics of the Rangemaster, the input and output of a positive ground pedal refer to the 9V of the power supply. This means that the pedal enclosure is connected to 9V, unlike the negative ground pedals. When the two pedals are connected together, the 9V and the ground of the power supply will be linked, causing a short circuit.
solutions for powering a vintage positive ground pedal
The simplest solution is to power the pedal as it was intended to be powered, with a battery. Especially since many vintage pedals do not have connectors for an external power supply!
If you have the possibility to connect a power supply, then you will have to use a power supply like a 1Spot, dedicated only to this pedal. You can also use power supply units, as long as the outputs are galvanically isolated from each other, like Cioks.
Finally, some manufacturers use a specific circuit integrated in the pedal called charge pump, which allows to generate a negative voltage from a classic power supply. These pedals can thus be connected to any power supply, while having a positive ground circuit inside. This is why we implemented this circuit in our Germanium Boost, based on a germanium treble booster with positive ground circuit.
the placement of vintage pedals in the effects chain
In the 60’s, guitarists used to plug the guitar directly into the amp with a cable. Indeed, wireless systems didn’t exist yet, and the first effects pedals started to appear. So they used at most one or two pedals between the guitar and the amp, as opposed to the huge and complex pedalboards we see today.
the problem of impedances
The electronics of a guitar is a circuit that looks simple at first glance, but has some complex characteristics. First of all, the pickup is composed of a coil of wire wound around a magnet. It therefore has all the properties of an inductor. Then, the proximity between each coil creates a parasitic capacitance, which forms a resonant filter with the inductance. Finally, the length of wire used has a certain resistance, which is not negligible.
So a guitar has a high output impedance, which will interact a lot with what is plugged in after. The first circuits (fuzz, treble booster, wah) were therefore designed to match this high impedance, the guitar electronics acting as an extension of the pedal circuit.
With the emergence of more and more effects pedals, problems started to appear when chaining several effects in series. This forced manufacturers to buffer the input and output of their effects (all pedals today have a high input impedance and a low output impedance).
The Tube Screamer schematic. You can see that the pedal integrates an input and output buffer, whose only purpose is to adapt the impedance, without providing any sound treatment. Source: Electrosmash.
The advantage of using buffered circuits is that you can put as many as you want in any order, while ensuring that the circuit always works the same. But this is not the case with vintage circuits, which are impedance sensitive. Connecting a vintage pedal after a buffered pedal that has a low output impedance will break the direct link between the guitar and the pedal. This will result in too much high end, but also a huge hum and a radical change in the pedal’s sound.
solutions for positioning a vintage pedal in the chain
The basic solution is to plug a vintage pedal first, directly into the guitar. If you need to put another pedal before, make sure it is true bypass, and do not use it at the same time as the vintage pedal. Also avoid wireless systems and active guitars, which have a preamp that acts as a buffer.
Another solution allowing to use a vintage pedal anywhere in the chain is to use a circuit simulating the impedance of a guitar pickup. With a transformer and a few components, it is possible to reproduce all the characteristics of a guitar pickup, while placing anything you want before it. That’s why we integrated this simulator directly into the Germanium Boost, allowing to place the treble booster anywhere!
vintage pedal bypass and true bypass
vintage pedal bypass
Early effects pedals were extremely simple, and the bypass technology for turning off the effect was no exception. The simplest solution was to split the signal path into two at the input of the effect, one of them passing through the effect. Then there was a simple switch at the output to choose the path without the effect, or the path with the effect. This is the simplest solution, requiring a single switch, easy to find at the time.
On this schematic of the Maestro FZ-1, you can see that the footswitch only switches the output. The input is always connected to the guitar, and will therefore interact permanently with the impedance of the guitar. This will have an influence on the sound, compared to if the guitar was connected directly to the amp. Another particularity of the FZ-1, a second switch allows to disconnect the power supply when the effect is off, which is not always the case with other pedals.
At that time, there was no consideration of the influence of the circuit when the effect was deactivated. One of the most obvious examples is the Uni-Vibe, which when turned off, does not bypass the circuit, but simply turns off the LFO circuit responsible for the oscillation of the effect. The result is an effect comparable to a fixed vibe, which no longer oscillates, but still affects the signal.
the introduction of true bypass and buffered bypass
Again, the real problem started to appear with the emergence of more and more pedals. By chaining pedals that color the sound, the signal was getting more and more degraded. The idea of adding a second switch at the input of the pedal appeared, allowing to disconnect the whole circuit by bypassing it. The signal is switched in and out at the same time, this is the principle of true bypass.
Here again, the solution is not perfect, because the number of contacts is doubled, which can slightly deteriorate the quality of the signal, especially with many pedals connected together. There are also impedances that can vary from one pedal to another and interact differently with the guitar, depending on which pedal is activated.
That’s how the buffered bypass appeared, which can be found in Boss or Ibanez pedals with the Tube Screamer. The buffered bypass consists in bypassing the effect circuit, while keeping the input and output buffers. The signal is not true bypass, but it allows to keep a buffer that has been designed to interact as little as possible with the impedance of the guitar, while avoiding losses in long cables.
hardwire bypass of vintage pedals, true bypass, and buffered bypass. source: stinkfoot.se
Modern buffered bypasses are therefore designed to avoid losses, but it is not necessary to have several of them in series, as they can cause a slight noise, which will be stronger the more buffered pedals there are. Hence the advantage of using a single buffer at the beginning of the chain dedicated exclusively to this application, and then using only true bypass pedals.
turning off a vintage pedal
So it’s easy to understand why there are many true bypass mods on some vintage pedals. It’s an easy modification to do and doesn’t change the character of the effect, while allowing to disconnect it completely. You can also choose to deliberately keep the original bypass to color the signal, like the Uni-Vibe which produces a kind of boost with subtle mediums.
To add a true bypass without modifying the pedal, there is always the solution of using a switcher. There are even some pedals whose only purpose is to offer a true bypass with an effect loop, to insert the pedal that does not have a true bypass. In both cases, you have to make sure that the loop is not buffered, and that nothing is placed before it, so that the pedal can interact with the impedance of the guitar.
conclusion
With this information, you now have everything you need to get the best out of your vintage pedals! To summarize, germanium pedals often need a dedicated power supply, or a fully isolated power supply. The battery is the safest way to power these pedals properly. Buffers, wireless systems, active guitars or any other device that breaks the direct connection between the guitar and the pedal should be avoided. Finally, most vintage pedals will color the sound even when turned off. The result can be interesting, but if not, you can use a switcher or a passive bypass pedal to fully disconnect the effect.
Don’t hesitate to share with us the most beautiful pictures of your board with vintage pedals, to see how you connected them according to your needs!
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Vintage pedals: how to connect and use them correctly?
If you’ve ever asked about some vintage pedals, you’ve probably heard about positive ground, plugging the pedal first after the guitar, or using batteries only. In this article, we’ll explain where these rules come from, and how to get the optimal use out of a vintage effect pedal.
vintage pedal power supply and positive ground
what is positive ground?
The first effects pedals were introduced in the 60s. At that time, germanium was widely used for the manufacture of transistors, before the use of silicon which has many additional advantages. So, the first pedal circuits were built with germanium transistors. These transistors were easier to produce in PNP format, i.e. operating with a negative current on their base.
One of the specificities of PNP transistors is that they need a negative supply to obtain this negative current. The idea is to consider as reference voltage the positive terminal of the power supply in the whole circuit, and to consider that the negative terminal is therefore a negative voltage of -9V.
Source: Electrosmash.
It doesn’t seem intuitive, but what you need to understand is that a voltage always needs to be expressed with a reference. In a 9V battery, saying that the (+) terminal is 9V doesn’t make sense. The correct formulation would be to say that the (+) terminal is 9V higher than the (-) terminal. We can therefore consider that the (+) terminal is our reference (0V), and in this case, the (-) terminal is 9V below, so -9V.
Basically, in the first circuit, the battery is connected in the opposite direction to the second circuit. Each pedal has its own battery, so they are isolated from each other, allowing each pedal to have its own reference.
The battery on the left is referenced to its (-) terminal. This results in +9V on its (+) terminal. The battery on the right is referenced to its (+) terminal. So we get -9V on its (-) terminal. Connecting a positive ground pedal with a negative ground pedal means connecting the two batteries as in the diagram above, each pedal having its own reference.
the problem of positive ground with power supplies
The problems due to positive ground started to appear with the emergence of power supplies for pedals, especially daisy chains. These power supplies allow to power several pedals from a single voltage source.
As you can see from the two schematics of the Rangemaster, the input and output of a positive ground pedal refer to the 9V of the power supply. This means that the pedal enclosure is connected to 9V, unlike the negative ground pedals. When the two pedals are connected together, the 9V and the ground of the power supply will be linked, causing a short circuit.
solutions for powering a vintage positive ground pedal
The simplest solution is to power the pedal as it was intended to be powered, with a battery. Especially since many vintage pedals do not have connectors for an external power supply!
If you have the possibility to connect a power supply, then you will have to use a power supply like a 1Spot, dedicated only to this pedal. You can also use power supply units, as long as the outputs are galvanically isolated from each other, like Cioks.
Finally, some manufacturers use a specific circuit integrated in the pedal called charge pump, which allows to generate a negative voltage from a classic power supply. These pedals can thus be connected to any power supply, while having a positive ground circuit inside. This is why we implemented this circuit in our Germanium Boost, based on a germanium treble booster with positive ground circuit.
the placement of vintage pedals in the effects chain
In the 60’s, guitarists used to plug the guitar directly into the amp with a cable. Indeed, wireless systems didn’t exist yet, and the first effects pedals started to appear. So they used at most one or two pedals between the guitar and the amp, as opposed to the huge and complex pedalboards we see today.
the problem of impedances
The electronics of a guitar is a circuit that looks simple at first glance, but has some complex characteristics. First of all, the pickup is composed of a coil of wire wound around a magnet. It therefore has all the properties of an inductor. Then, the proximity between each coil creates a parasitic capacitance, which forms a resonant filter with the inductance. Finally, the length of wire used has a certain resistance, which is not negligible.
So a guitar has a high output impedance, which will interact a lot with what is plugged in after. The first circuits (fuzz, treble booster, wah) were therefore designed to match this high impedance, the guitar electronics acting as an extension of the pedal circuit.
With the emergence of more and more effects pedals, problems started to appear when chaining several effects in series. This forced manufacturers to buffer the input and output of their effects (all pedals today have a high input impedance and a low output impedance).
The advantage of using buffered circuits is that you can put as many as you want in any order, while ensuring that the circuit always works the same. But this is not the case with vintage circuits, which are impedance sensitive. Connecting a vintage pedal after a buffered pedal that has a low output impedance will break the direct link between the guitar and the pedal. This will result in too much high end, but also a huge hum and a radical change in the pedal’s sound.
solutions for positioning a vintage pedal in the chain
The basic solution is to plug a vintage pedal first, directly into the guitar. If you need to put another pedal before, make sure it is true bypass, and do not use it at the same time as the vintage pedal. Also avoid wireless systems and active guitars, which have a preamp that acts as a buffer.
Another solution allowing to use a vintage pedal anywhere in the chain is to use a circuit simulating the impedance of a guitar pickup. With a transformer and a few components, it is possible to reproduce all the characteristics of a guitar pickup, while placing anything you want before it. That’s why we integrated this simulator directly into the Germanium Boost, allowing to place the treble booster anywhere!
vintage pedal bypass and true bypass
vintage pedal bypass
Early effects pedals were extremely simple, and the bypass technology for turning off the effect was no exception. The simplest solution was to split the signal path into two at the input of the effect, one of them passing through the effect. Then there was a simple switch at the output to choose the path without the effect, or the path with the effect. This is the simplest solution, requiring a single switch, easy to find at the time.
On this schematic of the Maestro FZ-1, you can see that the footswitch only switches the output. The input is always connected to the guitar, and will therefore interact permanently with the impedance of the guitar. This will have an influence on the sound, compared to if the guitar was connected directly to the amp. Another particularity of the FZ-1, a second switch allows to disconnect the power supply when the effect is off, which is not always the case with other pedals.
At that time, there was no consideration of the influence of the circuit when the effect was deactivated. One of the most obvious examples is the Uni-Vibe, which when turned off, does not bypass the circuit, but simply turns off the LFO circuit responsible for the oscillation of the effect. The result is an effect comparable to a fixed vibe, which no longer oscillates, but still affects the signal.
the introduction of true bypass and buffered bypass
Again, the real problem started to appear with the emergence of more and more pedals. By chaining pedals that color the sound, the signal was getting more and more degraded. The idea of adding a second switch at the input of the pedal appeared, allowing to disconnect the whole circuit by bypassing it. The signal is switched in and out at the same time, this is the principle of true bypass.
Here again, the solution is not perfect, because the number of contacts is doubled, which can slightly deteriorate the quality of the signal, especially with many pedals connected together. There are also impedances that can vary from one pedal to another and interact differently with the guitar, depending on which pedal is activated.
That’s how the buffered bypass appeared, which can be found in Boss or Ibanez pedals with the Tube Screamer. The buffered bypass consists in bypassing the effect circuit, while keeping the input and output buffers. The signal is not true bypass, but it allows to keep a buffer that has been designed to interact as little as possible with the impedance of the guitar, while avoiding losses in long cables.
Modern buffered bypasses are therefore designed to avoid losses, but it is not necessary to have several of them in series, as they can cause a slight noise, which will be stronger the more buffered pedals there are. Hence the advantage of using a single buffer at the beginning of the chain dedicated exclusively to this application, and then using only true bypass pedals.
turning off a vintage pedal
So it’s easy to understand why there are many true bypass mods on some vintage pedals. It’s an easy modification to do and doesn’t change the character of the effect, while allowing to disconnect it completely. You can also choose to deliberately keep the original bypass to color the signal, like the Uni-Vibe which produces a kind of boost with subtle mediums.
To add a true bypass without modifying the pedal, there is always the solution of using a switcher. There are even some pedals whose only purpose is to offer a true bypass with an effect loop, to insert the pedal that does not have a true bypass. In both cases, you have to make sure that the loop is not buffered, and that nothing is placed before it, so that the pedal can interact with the impedance of the guitar.
conclusion
With this information, you now have everything you need to get the best out of your vintage pedals! To summarize, germanium pedals often need a dedicated power supply, or a fully isolated power supply. The battery is the safest way to power these pedals properly. Buffers, wireless systems, active guitars or any other device that breaks the direct connection between the guitar and the pedal should be avoided. Finally, most vintage pedals will color the sound even when turned off. The result can be interesting, but if not, you can use a switcher or a passive bypass pedal to fully disconnect the effect.
Don’t hesitate to share with us the most beautiful pictures of your board with vintage pedals, to see how you connected them according to your needs!