Audio i2e

Questions and answers about AG2.0 / AG2.1

What is a buffer ?
A buffer is generally understood to mean a device with an input, an output and an intermediate, active electronics, which is looped into a signal chain.
At the same time, the signal fed into the input is made available again as unchanged as possible at the output.
But where is the meaning if nothing is changed?
The only thing that should remain unchanged is the signal itself (the waveform ...), electrical properties of the line or the source generating the signal are changed.
What are the electrical properties?
Each signal source, e.g. also the pickup of a guitar, has a certain output / internal resistance.
Each connected "consumer", e.g. a guitar amp or effects unit, has a certain input resistance.
The voltage originally generated by the signal source is now divided between these two resistors, in proportion to the size of the resistors.
Example: A pickup has an internal resistance of 10 kilohms and delivers unloaded (no "consumer" connected) a voltage of 1 volt. If I now connect this guitar to an amplifier with 10 kilohm input resistance, then the 1 volt split into 0.5 volts at the amplifier and 0.5 volts in the pickup. Only the 0.5 volts at the amplifier can be further processed (amplified), the 0.5 volts, which drop at the internal resistance of the pickup, are virtually lost.
If my amplifier has a much higher input resistance (for example, 1 megohm = 100 x 10 kilo ohms), then the voltage is divided equally favorably: 0.99 volts at the amplifier, only 0.01 volts are lost in the pickup.

Besides viewing:
The cable between guitar and amplifier also represents a consumer! It acts as a capacitor, which is parallel to the input of the amplifier and thus practically reduces its input resistance. And a capacitor is a resistor whose size depends on the frequency of the signal!
The higher the frequency, the smaller the resistance.
The combination of input resistance of the amplifier and parallel capacitor (cable) is thus at low frequencies perhaps still large compared to the internal resistance of the guitar, that is, there remains much tension for the amplifier, but at high frequencies may be much smaller, that is, it stands less Voltage for further amplification available. The frequency response of the guitar signal is distorted by the cable, high frequencies are attenuated to low frequencies, the guitar sounds dull!
The aim is to have the smallest possible internal resistance of the source. The smaller, the better the ratio to any input resistances of connected "consumers", and the less influence a frequency changing resistance of a cable has. Ideally, the internal resistance is "0" ohms, then it would not matter what is connected, it can always and for all frequencies the optimal output voltage can be used.
For a passive pickup, the ohmic internal resistance is initially dictated by the thickness of the wire and the number of turns. This resistance is in the range of several kilo ohms and would not cause any great corruption in the frequency response alone in connection with a connected cable.
This is true in the event that the volume pot of the guitar is fully turned on.
It looks quite different, however, when the pot is being adjusted. If it has e.g. a total value of 250-500kOhm and is limited to half output voltage, suddenly results in an internal resistance of the guitar of 125-250kOhm! And such a high resistance, together with the cable capacitance, definitely has an influence on the frequency response.
When connecting the guitar and the connected cable in addition to the attenuation of higher frequencies in conjunction with the internal resistance, another effect plays a role:
The pickup consists of a large number of turns of wire and, electrically speaking, also represents a coil. And this coil has the properties of an inductance, which forms a resonant circuit in conjunction with a capacitance (cable!). Such a resonant circuit has a higher output voltage at a specific frequency than at all other frequencies, namely at the so-called resonant frequency. With the same cable type and cable length, the location and amount of resonance on different guitars depends on the type of pickup and often forms the characteristic sound of this guitar. For a cable of average quality (average capacity), e.g. with a cable length between 3 and 6 meters the "typical" tone of the respective pickup. The resonance of a single coil is generally higher than that of a humbucker (the humbucker represents the larger inductance ...). Increasing the capacity of the cable decisively, either by using a different cable or by a substantial extension (the capacitance increases linearly with the length of the cable) shifts the resonance to lower frequencies on the one hand and higher frequencies on the other hand damped. One speaks of a "low pass with resonance point". The pickup quickly loses its characteristics. A Strat does not sound like a Strat ...
Now the buffer comes into play:
He picks up the signal from the pickup and passes it on as unchanged as possible, but no longer with an output resistance of many kiloohms but with an output resistance of only a few ohms, which is e.g. a reduction by a factor of 10,000-100,000 means! Due to this small output or internal resistance each subsequent load (cable, amplifier, effects) has only very little influence on the signal.
The ideal buffer also has a high input resistance to minimize the signal of the connected guitar. 

What is a booster ?
A "classical" buffer provides the voltage at its input as equal as possible at its output, so there is no gain or attenuation of the signal. Only an electrical property of the signal source, the internal resistance, is changed.
A booster is now a device that can amplify the signal, at best in conjunction with the desired buffer characteristic of the low-impedance output.
Sometimes it is advantageous if, in addition to the amplification of weak input signals (single coil), it is also possible to attenuate very high signal levels (humbuckers). Ideal would therefore be a device that provides the function of a buffer available (low-impedance output), and in addition either the input signal either attenuates or amplified, for example, adjustable by means of a potentiometer.

When and why do i need a buffer in my signalchain and where does it belong ?
As explained above, a "consumer" loads the output of a connected guitar, it is attenuated. However, almost all as "consumers" candidate devices (amplifier, effects) have a relation to the internal resistance of the guitar large input resistance, so that the load remains very small in practice. However, the "almost" in the previous sentence points to a crucial limitation, namely the cable between the guitar and the connected consumer.
This represents with its capacity (capacitor!) A frequency-dependent resistance. While a "normal" (resistance) load by another consumer, which only lowers the level overall, is still to get over (you simply amplifies a bit more ... ), a frequency-dependent (capacitor) load is extremely disturbing, because not only the volume but the sound of the guitar changed. High notes are more heavily attenuated than the bass (the cable capacitor has a smaller resistance at high frequencies), the guitar sounds less vivid, dull, or even dull. And the change is retrospectively not necessarily easy to undo because it depends on the size of the capacity of the cable. Depending on the type of cable used and the cable length, the conditions are always different. As already mentioned elsewhere, this effect occurs especially in connection with a regulated volume control, as this greatly increases the internal resistance of the Gitaare. The situation can be improved with the help of a "treble bleed" capacitor, which is connected in parallel to the poti in the guitar. Perfectly this "trick" works but only at a certain Potistellung and a specific cable capacity.
The other negative influence of the cable capacity, namely the shift of the pickup resonance towards lower frequencies, however, can not be practically prevented or reversed. Here, overall, the original character of the instrument is lost.

Ok, after so much theoretical preface comes here the practice:
If the guitar is directly connected to an amplifier via an average cable of 3 to 6 meters in length, then the use of a buffer is not absolutely necessary. The characteristic tone of the pickup or the guitar is retained or is just being shaped.
But if I connect the same guitar with the same cable first with an effect unit and connect this with a further 6-meter cable to the amplifier, then the use of a buffer can be installed.
As long as the effect device is switched on, it usually acts as a buffer, ie it has a relatively low-impedance output and the subsequent cable to the amplifier is not a problem.
But if it is switched off and has a "True Bypass" circuit, then its input and its output are now directly connected. The cable to the amplifier is right in line with my cable to the effects unit and the total capacity has risen sharply, possibly doubled, and the sound of the guitar can be greatly changed.
The more effect devices are connected in series and the more cables are in between, the greater the total capacity. Depending on which of the effects have a true bypass and where they are in the signal chain, there are always different circumstances.
Here, the buffer can provide a crucial help if it is the first device in the signal chain. The guitar is connected to the input of the buffer with the cable that creates the characteristic sound of the pickup. Its output then drives all the rest of the effects and amplifiers. It no longer matters whether and which effects have a True Bypass, whether they are on or off and how long the cable to the amplifier is ultimately ... The Buffer ensures defined ratios, without changing the guitar sound through the buffer itself.
i2e audio offers here with the device series AG2.x usable buffers, which also make a gain (booster) or weakening of the guitar signal possible.
Vorrausgesetzt is here, of course, that a switched effect device also has a low-impedance output, which can drive a ev. Longer cable to the amplifier without any problems.
If this were not the case, a buffer could also be needed at several points of the signal chain (or you change the "weak" effect device for a better one from another manufacturer ...)
In the described scenario it is assumed that at least the first cable from the guitar to the buffer does not distort the sound of the guitar, but rather gives the pickup with optimal capacity the characteristic sound.
If this is not the case and the first cable from the guitar to the buffer, to the effect chain or directly to the amplifier is already very long (for example 6 meters) and therefore has a large capacity, the sound of my guitar suffers here. The resonance possibly shifts downwards massively and the higher tones are markedly attenuated. Here, no buffer at the end of the cable would help anymore, because the damage is already done and can not be repaired by the buffer.
If it is not possible to replace the cable or if you basically do not want to make the guitar sound dependent on the connected cable, there are two options:
The pickup of the guitar must be supported by an active electronics either directly in the guitar itself (active pickup) or in the immediate vicinity of the guitar. Here the
AG1.0 / The PURR could represent a solution.

Does the AG2.x change the sound of my guitar ?
If the AG2x is switched off, a multiple switch (AG2.0) or a relay (AG2.1) connect the input directly to the output. All other circuit parts of the AG2.x are disconnected. The sound of the guitar is in this case not changed at all, everything behaves as if no AG2.x in the signal chain ..
If the
AG2.x is switched on, but the Gain control is in the middle position, the following condition results: The guitar pickup is only with the capacity of the cable between the guitar and AG2.x, but not with the capacity of cables between subsequent effect units or the cable to the amplifier loaded. As a result, higher frequencies are attenuated less strong and also shifts the resonance of the pickup to higher frequencies. The guitar sounds more "airy", the pickup is closer to its "ideal", typical sound.
If the Gain control is moved out of the middle position, the signal also experiences either a weakening or a gain, but the positive characteristics of a "buffer" are retained in any case, the basic sound of the guitar is not changed.

Why does the AG2.x has no battery supply ?
The preferred application of AG2.x is to be used as the first member of an effect chain. Here are usually used anyway further power supplies for the effect devices, either several single power supplies or a multiple supply, so that a further supply for the AG2.x should not be a problem. A suitable single power supply is included in the AG2.x.

What do you think about the myth of a  "neutral" buffer ?
There are actually manufacturers who boast of offering a "neutral" buffer. The guitar sound would not be changed by the buffer ...
The fact is: Whether realized with transistor or operational amplifier, it is really the simplest exercise today to build a buffer that has a linear frequency response in the frequency range of a guitar, ie between 80Hz and 10kHz and has only inaudible self-distortion!
At a time when there were only germanium transistors, things looked different. Those who boast about being able to offer a "neutral" buffer today are more likely to struggle with replicating old schematics than are familiar with the state of the art nowadays.
But is "neutrality" really that important? Of course I do not want a "distortion" if I deliberately loop a "buffer" into my signal chain, but often a (slight) correction of the frequency response is desired, usually in the form that higher frequencies are slightly amplified ("treble boost").
i2e audio offers different buffers. Operational amplifiers are used to achieve the highest "neutrality", but also discrete FET circuits, which amplify less linearly and thereby add harmonics. It may be possible to prove that it has a technical influence, but its influence on the sound remains "subtle", the signal always remains "musical".  

Does the AG2.x help me with my bass ?
Even though the bass is supposed to generate mostly low notes, the overtones play a crucial role in the sound, especially with unpolished strings and plectrum playing. That's why the AG2.x also audibly changes the bass spectrum and the resonance behavior of the pickups with long cables. In addition, if the output level is too low, the booster function can be very useful. 

Can i use the AG2.x also with my active guitar / my active bass ?
The active guitar / bass does not really need the function of a subsequent buffer. The buffer is already built into the guitar / bass. But as a booster, the AG2.x can also support an active guitar / bass effectively. 

Whay is the AG2.x relatively expensive ? My xyz pedal can do more and costs much less ?
The AG2.x was developed in Germany and is manufactured in relatively small quantities also completely in Germany (including housing processing and PCB production). Only high-quality components are used. In fact, the price is based on a still moderate calculation and none of the participants gets rich by the AG2.x. Less price is not possible, otherwise we would not be able to pay our rents and then develop new, interesting devices. See in this context also our pickup-resonator AG1.0, / The PURR, the 2-channel guitar interface ESTE or the amplifier JESS, whose new concepts were not yet so on the market available.
Or rather buy a cheap device coming from the Far East? Are ok too! But why are they so incredibly cheap? Because of the huge quantities? Sure, that matters a lot, but still you could not make them here in Germany for the same price.
Do not also problematic production conditions, with regard to the environment and sustainability (after us the deluge ...), and things like catastrophic working conditions and starvation wages play a role? And should states that have at least questionable political conditions prevail at all economically? The main thing is the whopping Central Europeans can buy a bunch of cheap effects devices?
And we want back our cheap lottery !

Are you boutique ?
What is boutique? If you're doing a Marshall / Fender circuit diagram for the hundredth time, you've changed some component values slightly, using noisy carbon press resistors and hand-soldered voodoo capacitors to offer a "totally different-sounding" amplifier at an outrageous price? Or if you imagine a TL071 operational amplifier with diodes in the negative feedback as the non-plus-ultra, of course shed in black gunk, otherwise everyone could see what is behind it, and also plays this great guitarist XYZ this part exclusively, and costs of course a multiple of an equivalent brand pedal (the green one ...)?
If this is boutique, then we are not! We do not copy existing equipment and issue it as a novelty, but are always looking for new ways. The focus is always on the instrument, our devices should support, ideally be part of the instrument. Prices are calculated according to quantity and effort fair and not determined with dice. 

Can i use the AG2.x also in conjunction with the passive piezo pickup of my acoustic guitar ?
Piezo pickups are inherently a relatively large capacitance themselves (e.g.,> 20nF). Therefore, the influence of a relatively small capacity of even a long cable (for example, 1nF) is rather small. However, a piezo pickup benefits from the highest possible input resistance of an amplifier (... apart from special piezo amplifiers, keyword charge amplifier ...), as it can only transmit low tones sufficiently. If the amplifier used does not have a sufficiently high input resistance and therefore lower tones are rather weak, then the
AG2.x can possibly help. He has an input resistance of at least 1MOhm and is therefore still quite good for the connection of a piezo. It may also be useful to use the boost function of the AG2.x. He also makes the connected at its output to the amplifier and possibly long cable less susceptible to interference, because he controls it low impedance.
Conclusion: The
AG2.x is not specifically designed for the requirements of a passive piezo pickup, but depending on the amplifier used (and the quality of the cable used to the amplifier) ​​can improve the frequency response (low frequencies) and the signal to noise ratio. 

 


i2e'17