People often seek guitars with low impedance because they believe this will preserve an unadulterated tone; however, this may not necessarily be the case.
Each electronic component in a signal chain brings with it changes to the guitar’s frequency response, particularly pickups and long cables.
Impedance
Impedance is the combination of resistance and reactance in an electrical circuit; it represents its overall opposition to alternating current (AC).
A guitar pickup may seem like a simple device, but its construction and magnet choice can have a significant effect on its tone. Some guitarists, like Dave Gilmour and Eric Clapton use single-coil pickups for bright tone while other prefer humbucking pickups to produce deeper sounds. Pickup selection may also impact amplifier tone – certain amplifiers work best when coupled with low impedance pickups.
An impedance of a pickup can be measured in terms of its number of turns, magnet strength and materials used to construct it. Impedance plays an integral role in determining its ability to transmit signal with minimal distortion while protecting high frequencies from being lost during transmission.
Temperature can have a considerable effect on the impedance of a guitar pickup, and an ohm reading on a meter does not always provide an accurate representation of its true impedance. For instance, when the guitar is colder its copper wire vibrates less and presents less resistance; once warm however its coil vibrates more and this causes its resistance level to rise more sharply and the reading on your meter to go up.
Another factor affecting a pickup’s impedance is cable load. Long cables tend to present an impedance load that’s high, while shorter cables may lower an amp’s input impedance.
Impedance changes with frequency because different frequencies interact differently with capacitors and inductors, as different frequencies interact differently with capacitors and inductors. For instance, as frequency of signal increases resistance presented by capacitors decreases while coil inductance increases; this allows higher frequencies to experience lower resistance on their way towards output while lower frequencies are diverted away towards ground.
Z-Mode preamps address this impedance variation by including an electronic buffer to protect the natural pickup output of your guitar from any changes down the line, offering a reliable way to avoid pickup mismatching and its consequent tone changes.
Inductance
As electricity passes through a pickup’s coil windings, it creates magnetic fields which interact with strings to cause them to vibrate and produce sound. The number of coil windings, thickness of wire used and types/numbers of magnets within it all affect its sound; distance from strings also plays a part; generally closer strings produce brighter sounds while those further away usually produce duller tones.
Combinations of these factors determine a pickup’s impedance. Loads with higher impedance tend to produce more treble, while those with lower impedance have more bass; neither one is necessarily better; they just produce different tones.
Impedance is essential when connecting guitar pickups to devices with high input impedances such as amplifiers or hi-z inputs on audio interfaces; its value determines how much signal passes between these devices.
Pickups can be assessed for impedance by measuring their DC resistance; however, this doesn’t indicate how loudly they’ll sound; rather it indicates the difficulty of forcing an electrical current through their coil.
An impedance of 100K Ohms would impose an extremely low power-transfer capacity and impedance; conversely, lower DC resistances have lower inductances that contribute to greater outputs.
One way of assessing a pickup’s performance is by studying its frequency response curve. This chart displays how much output voltage the pickup generates at each frequency; flat frequency response produces pure sound while one with an audible buzz will not.
Experience is the best way to understand how a particular pickup will sound, and guitar shops typically stock various models that allow you to try it out before purchasing. Furthermore, you can experiment with changing settings of your pickups; such as setting your bridge pickup low and tilting either the bass or treble side of the neck pickup to emphasize its features.
Capacitance
Capacitance changes the frequency of its resonant peak (though less significantly than with inductance). Furthermore, capacitance reduces DC resistance in the coil which means more electrons will pass through it and into the circuit – this effect has less of an immediate impact than its counterpart but still makes a noticeable change to guitar tone.
Resonant peak of the pickup is determined not only by inductance and capacitance but also length, number of turns and magnet strength. While inductance and capacitance will track with length closely, number of turns and magnet strength have more to do with output than their ohm readings.
An ohm reading may not always provide the most reliable measurement of pickup performance; but it can still provide useful data; for instance, when coil inductance and capacitance exactly match an amplifier input impedance value, maximum power will be available across all frequencies.
As previously discussed, however, this isn’t always feasible and many factors can come in the way. A guitar cable’s capacitance increases with length (2*length 2*capacitance). This can have an impactful impact on sound quality when connected via long cables to amplifiers.
As such, manufacturers include small preamps in active pickups in order to mitigate impedance mismatches between pickup and amp and avoid impedance mismatching issues.
One final point to keep in mind is that the impedance of a guitar pickup may differ significantly from that of its corresponding input to an amplifier’s preamp input, due to guitar amplifiers (mixers, stomp boxes etc) being designed for higher impedance loads such as 1M Ohm or more loads – so its output may exceed their ability to handle without distorting into distortion.
Resistance
Resistance refers to the part of an impedance pickup’s impedance that opposes electricity flow. It measures how much a coil’s resistance resists pushing electrical current through it at any given voltage applied, measured in ohms (or thousandths of an ohm = kilo-ohms).
As can be expected, different materials offer differing levels of resistance. For instance, copper wire has more resistance the larger its diameter is; its thickness also affects how much resistance there is.
Resistance of a pickup can be altered by several factors, including its number of turns in its coil and magnet size, as well as using different pole pieces such as steel or AlNiCo pole pieces to influence it. Once calculated, its DC resistance gives an idea of its tone potential.
One major downside of guitar pickup ohm readings is their inaccuracy when applied to amplifiers or devices with high input impedances like hi-z inputs on audio interfaces, due to other elements in the circuit affecting how resistance flows through it and thus impacting signal flow.
Example: If a humbucker has high DC resistance, it may not have enough signal available to push an amplifier into overdrive or distortion; on the other hand, single coils with lower DC resistance will more easily push an amp into overdrive or distortion even with smaller magnets or less turns in its coil. Due to all this variability in instrument responses to power amps and their respective preamps, having some kind of electronic buffer like Z-Mode preamp is ideal; it handles all this by keeping input impedance consistent between instruments and amps while keeping input impedance levels consistent across their chains from bass to amp.
Impedance refers to resistance for alternating current signals (or signals). Mismatching of impedance will prevent maximum power transfer and may lead to noise, distortion or other unwanted side effects.
The humble guitar cable introduces capacitance; this increases with length as well as pot type (linear versus log taper), altering pickup impedance as a result.
Inductance
Impedance and guitar pickups both depend heavily on inductance for proper functioning. Inductance measures how much current can be generated by the pickup, which is vital given that voltage is dependent upon current, as is evidenced in physics by any sudden spikes or dips in voltage without an equally rapid change in current. A pickup with high inductance will produce substantial current flow resulting in significant voltage shifts as a result.
Inductance measures the magnetic flux surrounding coils inside of a magnet, with different magnets, pole pieces and coil windings having differing inductance values. More magnetic flux around coils typically means higher inductance due to current passing through them creating another magnetic field that pushes back against it via Lenz’s Law and produces resistance (technically known as reactance in this context).
Pickups with higher inductance tend to produce more resistive voltage, leading them to sound louder and have greater gain than pickups with lower inductance. Furthermore, their inductance affects frequency response – as we will discuss later.
Capacitance is also crucial when it comes to pickup tone, but less so than inductance. This is due to how capacitance only accounts for about one fifth of its overall capacitance when used – your guitar cable adds additional capacitance that typically increases three or four times larger than what the actual pickup offers.
Capacitance plays an important role in how much of a signal from your pickups reaches your amplifier. A 1-kOhm amplifier input impedance will transfer 99.9 percent of pickup signals (assuming all other factors remain constant); with higher impedance amps only transmitting 50%. As much of your pickup’s signal should reach your amp as possible!
Capacitance
A capacitor consists of two electrodes connected by an electrolytic dielectric material and separated by an air gap, or dielectric layer. They are constructed by layering ceramic and silver alloy electrodes until reaching their specified capacitance value based on voltage, current, and frequency requirements.
Most guitarists don’t realize it, but the capacitor connected to their tone pots (or between volume and tone in active guitars) has a significant effect on the bass tone. By altering its value, guitarists can access new sounds not previously achievable with previous settings of their tone control.
A capacitor is usually connected in parallel with the pickup, increasing its impedance. As impedance increases, more frequencies that you don’t want to hear may enter through interference; this can result in harsh or shrill tones depending on its construction and type of pickup used.
One factor that can alter the capacitor value is temperature of its coil. Copper wire ions vibrate more when exposed to higher temperatures, and this results in different ohm readings. However, it should be remembered that an ohm reading only represents DC resistance against pushing electric current through a pickup coil.
Factors influencing capacitance include voltage rating, dielectric constant and how close together its plates are. A thicker dielectric allows more electricity to pass between its plates of the capacitor but this usually causes it to expand further; to counter this effect electrodes must often be brought closer together in order to decrease space taken up by their capacitance.
An often-held misconception about capacitors is that their value can be altered simply by heating or cooling down their circuit, but this is simply untrue! Although temperature does have some bearing on its DC reading, this has nothing to do with how well it performs compared to similar-rated and dielectric constant capacitors like Electrocube AM or PM series models. To maximize performance it is therefore vital to select high quality models such as these for best performance results.
Resistance
A guitar pickup consists of magnets, wire coils and some plastic and metal components; how those elements are configured has an immense effect on tone. For instance, high output pickups tend to feature thousands of turns (windings) of wire for coil resistance-increasing purposes that contribute significantly to its impedance rating.
Single coil pickups typically feature much lower resistance due to having only a single or very few coil windings, thus producing much lower ohm readings with a multimeter than that of a humbucker pickup.
Low resistance contributes to a pickup’s ability to transfer current efficiently, as well as its sensitivity to feedback. But other factors also come into play here — for instance how tightly packed together coils are packed together and whether they have any magnets installed (along with whether or not vacuum impregnation occurs).
If you’re using a bass amp designed for magnetic-based guitar pickups, it is ideal that they all possess similar impedance values to ensure optimally loaded input (as opposed to overloaded input, which could negatively alter your tone).
Impedance matching is critical in order to maximize pickup performance without overstraining your amplifier or overheating it due to excessive loading. Furthermore, matching helps safeguard amps by decreasing their chances of overheating due to excessive strain.
Resistors provide another level of tonal shaping options beyond what pickups, capacitors and pots can. As an example, here’s an illustration.
To improve their compatibility with single coil pickups, add a 1Meg resistor in parallel with your volume pot to lower its value from 500K to 333K and thus increase current transmission capabilities. This trick can work for both linear and logarithmic pots.
Frequency Response
Ohm readings from pickups provide us with an idea of their inductance and resistance; however, that doesn’t tell us much about its tone; that depends on its construction – how big/many turns, coil size or even number can influence its inductance (more turns = more inductance), but other factors also impact its tone such as tuning or cable length can all have an effect.
Changing the number of windings around a coil can alter its magnetic field strength and alter inductance and frequency response, altering inductance as a result and thus sound. Furthermore, material used for winding as well as any ferrous materials attached will have a dramatic impact on inductance – including metal baseplates on Telecaster pickups or even screws that alter its inductance by up to one Henry (which can make an audible difference).
Many people assume that more windings on a pickup will translate to higher output, but this is not always true. Windings increase coil resistance, necessitating additional power from higher frequencies in order to push through it. Low-impedance pickups present less of a load on signals passing through them and allow higher frequencies more easily pass through.
Preamp choice also plays a large part in frequency response. Some valve preamps with higher input voltage can produce distortion when driving low output impedance pickups too hard for their design; other preamps may alter tonality by offering different forms of gain or feedback loops and presence/tone pot adjustments which have significant impacts on frequency response of guitar pickups.
Finalize your bass rig by adding a filter that rolls off high frequencies. Most bass instruments don’t rely on upper harmonics to cut through a mix, and by filtering these off it removes a potential problem and helps your bass stand out more. It is an efficient yet simple solution to making your bass instrument shine in any mix environment.