Impedance and the First Three Feet

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title: "Impedance and the First Three Feet" slug: "impedance-and-the-first-three-feet" category: "Electronics" published: "2026-05-24" description: "Why the cable between your guitar and your first pedal is doing more to your tone than most of the gear on your board — and what to do about it." authors:

• "Suede Labs"

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The single most common source of tonal degradation in a guitar rig is the unbuffered cable run between the instrument and the first pedal. It is also the cheapest to fix.

The Problem

A passive guitar pickup has an output impedance that swings with frequency, typically peaking somewhere between 5 kΩ and 25 kΩ depending on pickup design.[^1] Any capacitance downstream forms a low-pass filter with that source impedance. The cable is the dominant capacitance in the chain — roughly 30 pF/ft for low-grade cable, down to about 19 pF/ft for premium audio cable.

A 20-foot cheap cable presents roughly 600 pF of shunt capacitance. Combined with a typical humbucker source impedance, this places the rolloff knee in the audible top end — sometimes as low as 4 kHz.

The Math

The treble rolloff frequency is approximately:

f₋₃dB ≈ 1 / (2π · Rₛ · C)

For a 15 kΩ source and 600 pF cable:

f ≈ 1 / (2π · 15,000 · 600e-12) ≈ 17.7 kHz

That looks safe. The trap is that the pickup is not a resistor — it is an LCR resonant network. The audible "sparkle" of a Stratocaster bridge pickup sits on top of a resonant peak somewhere between 3 and 6 kHz. A long cable's capacitance combines with the pickup's own inductance to drop that peak's amplitude and shift it lower in frequency, where it loses the perception of clarity.[^2]

What a Buffer Does

A buffer is a unity-gain amplifier with high input impedance (typically 1 MΩ) and low output impedance (typically under 1 kΩ). Place one early in the chain and:

• The pickup sees only the buffer's 1 MΩ load → no audible high-end loss
• Downstream cable capacitance now interacts with the buffer's low output impedance instead of the pickup → the same 600 pF cable now has its rolloff knee well above 100 kHz

In other words: the buffer moves the bottleneck out of the audio band.

When Not to Buffer

Buffers are not universally good. Specific cases where you want the pickup running into the next device directly:

• Vintage germanium fuzz — Fuzz Face and friends rely on pickup interaction for their volume-knob cleanup behavior. A buffer flattens this.
• Treble-bleed-style volume controls — these are tuned for the specific impedance the pickup presents. Buffering changes the math.
• Players who deliberately want darker, woolier top end — sometimes that rolloff is the sound.

Practical Rule of Thumb

• Less than 10 ft of cable, premium quality: passive run is fine
• 10–20 ft, mixed-quality cable: buffer at the front of the board
• More than 20 ft, or running into a switcher with long internal paths: buffer at both the pickup end and downstream

Recommended Topology

Tuner pedals often have always-on input buffers. Placing a tuner first solves the problem incidentally — provided the tuner's buffer is reasonable. Most modern ones are.

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[^1]: Source impedance depends on the pickup's winding, DCR, and the frequency of interest. Treat published "DC resistance" as a rough proxy, not a number to design against.

[^2]: This is the classic argument for why short, low-capacitance cables sound "brighter" than longer ones. The effect is real and measurable.