Understanding Guitar Impedance and Impedance Matching
Any electrical circuit has an inherent impedance, and electric guitars or electrified instruments are no different. There are exceptions to this rule, but most often the manufacturer of these "different" components has designed other components to change the system to standard high impedance.
Magnetic (High impedance)
High impedance is the standard output for an electric guitar. Most amplifiers and other electric gizmos that players use are designed to work with high impedance magnetic pickups.
Piezos (Ultra high impedance)
Transducers are ultra high impedance devices. Therefore, to attain maximum sonic performance, a preamp/buffer must be used. A buffer takes the ultra high impedance signal and converts it to a standard high impedance signal which most guitar amps, PAs and recording equipment can handle.
Many players use a "stomp box" effects unit between the guitar and the amp or PA, instead of an onboard or external preamp/buffer. Since many floor effects can accept an ultra high input impedance and deliver a standard high impedance output, they can be used as a buffer. Graphic or parametric equalizers are a logical choice, as they offer frequency control and buffering.
Magnetic (Low impedance)
The most common low impedance magnetic pickups are the "active" pickups sold by EMG and other specialized manufacturers. They differ from high impedance designs in that they typically use fewer turns of a lower gauge (thicker) magnet wire. These coils have a low DC resistance, which translates into a very low output, but very wide frequency response.
To compensate for the extremely low output and to buffer the signal to high impedance, these manufacturers build small preamps (often sealed inside the case of the pickup) that are powered by an onboard 9-volt battery. This is where the term "active" comes from. These small preamps are very clean, and boost the output of the pickup, often to very high levels. Typically, high impedance pickups never break the 1-volt output range, while some low impedance designs exceed 2 volts. Some of these pickups are designed to be VERY hot, which will drive the preamp section of a guitar amp very hard. This is desirable for high-gain rock-n-roll.
A few makers (Alembic is the most notable) retain the low impedance signal out of the guitar and send it to specially designed amps, or often directly into PA boards. PAs are designed to accept low impedance inputs, as most good microphones—for improved frequency response—are low impedance.
How Impedance Affects Your Guitar’s Tone
Impedance affects guitar tone primarily by influencing how the guitar signal passes through cables, pedals, and into the amplifier. High impedance, typical of passive pickups, results in a weaker current signal that is more sensitive to cable length and the presence of multiple pedals, often causing treble loss and a darker, duller tone due to resistance and capacitance in the signal chain. To preserve the clarity and brightness of the tone, it is ideal for the amplifier input (load impedance) to be much higher than the guitar's pickup output impedance (source impedance), generally by a factor of 10 or more.
High vs Low Impedance in Your Signal Chain
High impedance pickups tend to drive amplifiers harder, creating a sharper and more aggressive tone, whereas low impedance pickups produce a cleaner, smoother sound with less susceptibility to signal degradation over longer cables or complex pedal setups. In setups with many pedals or long cables, low impedance signals maintain tone strength and clarity better. Buffers or pedals with low input impedance can help maintain signal integrity by reducing signal loss.
How Cable Length and Capacitance Change Your Tone
Cable capacitance and resistance also interact with impedance to shape tone; longer or lower quality cables increase capacitance, which rolls off high frequencies and makes the tone darker. Thus, impedance matching and minimizing cable length or using buffers is key to retaining a true, dynamic guitar tone.
Bring Your Guitar’s Tone to Life with StewMac
Understanding impedance and impedance matching is the key to unlocking your guitar’s true sonic potential. Whether you’re wiring a classic single-coil setup, installing a piezo pickup, or experimenting with active electronics, the right tools and components make all the difference. At StewMac, we offer everything you need—pickups, guitar wiring kits, expert guidance, and more—to help you craft the exact sound you’ve imagined. Explore our vast selection of guitar electronics and luthier tools, and rely on StewMac for support every step of the way on your guitar journey.
