Electric Guitar Circuits

High Impedance Matching (Piezos)

Matching the very high impedance of piezo or other very 'hot' guitar pickups is crucial for optimizing sound quality due to several technical factors.

Piezo pickups, which utilize a layer of piezo-electric crystals to convert mechanical vibrations into electrical signals, possess an inherently high output impedance. Impedance is a measure of opposition to the flow of electrical signals, and in the case of piezo pickups, it represents the resistance to the signal flow from the pickup into the subsequent audio system.

When the impedance of a piezo pickup is not properly matched with the input impedance of the following audio equipment, several issues arise that can degrade sound quality and here's why:

Signal Loss:

Impedance mismatching causes a phenomenon called "signal loss" due to the interaction between the source impedance (piezo pickup) and the load impedance (audio equipment).

If the input impedance of the audio system is significantly lower than the output impedance of the piezo pickup, a portion of the electrical signal is lost in the form of reflections and signal degradation. This leads to a weaker, less defined signal reaching the audio system, resulting in a poor sound quality.

Frequency Response Irregularities:

The frequency response of a piezo pickup is affected by its output impedance and the input impedance of the audio equipment. When there is a significant mismatch, it can lead to irregularities in the frequency response, causing certain frequencies to be emphasized or attenuated. This results in tonal imbalances and an altered representation of the original sound.

Distortion and Noise:

Impedance mismatching can introduce unwanted distortion and noise into the signal chain. When the load impedance is too low, it can cause excessive current flow from the pickup, resulting in distortion. Additionally, the mismatch can lead to increased susceptibility to electromagnetic interference and noise pickup, degrading the signal quality further.

By matching the very high impedance of piezo guitar pickups with the appropriate input impedance of the subsequent audio equipment, these issues can be mitigated. A high-impedance input, often referred to as a "high-Z" input, typically has an impedance of several megaohms (MΩ), which is similar to the output impedance of piezo pickups.

Impedance matching allows for maximum power transfer, minimizing signal loss, preserving the frequency response, and reducing distortion and noise, resulting in a higher quality and more faithful reproduction of the guitar's sound.

Buffering

Buffering guitar pickups can greatly improve the quality of the sound by making it clearer, more balanced, and free from unwanted noise.

To understand this, let's start with how a guitar pickup works. A pickup is a device that captures the vibrations of the guitar strings and converts them into an electrical signal. This signal then travels through the guitar's electronics before reaching the amplifier or other audio equipment.

However, the electrical signal from the pickup is very weak and can be easily affected by different factors, such as the length of the cables or the electronics inside the guitar. These factors can introduce interference and degrade the quality of the sound.

When we buffer the pickups, we add a small electronic circuit called a buffer between the pickups and the rest of the guitar's electronics. This buffer acts as a signal booster, strengthening the electrical signal from the pickups.

Buffering helps preserve the high-frequency details and nuances of the sound.

Without buffering, these details can get lost or muffled, resulting in a less defined and less vibrant tone.

Buffering reduces the impact of cable length and other external factors on the sound.

When the signal travels through long cables or encounters other electronics, it can lose strength and clarity. The buffer helps to maintain the signal's integrity, so you get a more consistent and faithful representation of your guitar's sound.

Buffering can reduce noise and interference.

The buffer circuit has the ability to isolate the pickups from other components in the guitar, minimizing any unwanted humming, buzzing, or other electrical noise that can affect the sound quality.

By buffering the pickups, we can ensure that the signal from the guitar is strong, clean, and free from interference. This results in a more vibrant, balanced, and detailed sound, allowing your guitar to shine and be heard the way it was intended.