Free Calculator

RCA & Phono Cable Treble Roll-off Calculator

High cable capacitance forms a low-pass filter against your cartridge or preamp output impedance. This calculator finds the −3 dB frequency where treble starts rolling off and plots the full curve so you can spot cables that are quietly killing your high frequencies.

Why it matters: a 47 kΩ Moving Magnet cartridge with 300 pF of total loading rolls off at roughly 11 kHz - well inside the audible band. Lower cable capacitance, shorter runs, and the right phono-stage input loading keep the treble intact.

Cable capacitance (pF/metre)

Budget RCA: 80-200 pF/m. Quality cable: 50-100 pF/m. Phono-grade: 20-60 pF/m.

Cable length

Source output impedance (ohms)

MM cartridge: 47 kΩ typical. MC: 10-100 Ω. Preamp line out: 50-600 Ω.

Phono-stage input capacitance (pF)

Typical: 100-300 pF. Check your phono preamp manual.

How cable capacitance steals treble

The RC low-pass filter

Any capacitor in parallel with a load and a source resistance forms a low-pass filter with corner frequency f = 1 ÷ (2π × R × C). For an MM cartridge at 47 kΩ with 300 pF total loading, the −3 dB point lands at roughly 11.3 kHz - audibly inside the music band.

Total capacitance = cable capacitance × length + phono-stage input capacitance. Shorter, lower-capacitance cables move the corner up. So does picking a phono stage with lower input loading.

Practical loading targets

Moving Magnet cartridges are typically optimized for 150-300 pF total loading. Keep total cable + input capacitance under 250 pF to put the −3 dB above 17 kHz. Some cartridges (Shure, Audio-Technica) publish ideal loading; honour those numbers.

Moving Coil cartridges sit at 10-100 Ω output impedance, so cable capacitance barely registers - the corner stays north of 100 kHz even on long runs. The cable problem is mostly an MM problem.

Typical capacitance, by cable type

Capacitance per metre is the spec to chase if you have a phono front-end. Multiply by length, add the phono stage's input capacitance, and you have the load on the cartridge.

Cable type	Capacitance	Where it shows up
Generic shielded RCA (PVC dielectric)	120-250 pF/m	Bargain-bin AV cables. Worst on long runs with MM cartridges.
Standard hi-fi interconnect	80-130 pF/m	Mid-tier RCA. Fine for line-level, marginal for MM phono.
Quality interconnect (PE / PTFE dielectric)	50-90 pF/m	Reference-grade audio cable. Headroom on phono.
Tonearm cable (specialist phono)	20-60 pF/m	Designed specifically for cartridge loading.
Studio mic cable (Star-Quad XLR)	35-60 pF/m	Pro audio long runs. Low capacitance is part of the spec.
Coaxial digital (75 Ω SPDIF)	~67 pF/m	Capacitance is fixed by the 75 Ω geometry. Not the issue here.
USB cable	N/A (digital)	Capacitance irrelevant - bit-stream is regenerated by the receiver.

FAQ

Cable capacitance and treble roll-off FAQ.

Why phono cable capacitance kills high frequencies, what specifications to look for, and when it stops mattering.

Why does cable capacitance matter for phono cartridges?
Moving-magnet (MM) phono cartridges are spec'd for a specific load capacitance (typically 100-300 pF including the phono cable). High-capacitance RCA runs push the resonant peak below the audible band, killing treble. The calculator finds where the -3 dB roll-off lands for your cable length and source impedance.
What is a safe cable capacitance for line-level RCA runs?
Below ~150 pF total for short (<1 m) runs is fine for any modern source. Long runs (3-5 m) start to need lower-capacitance cable: aim for under 30 pF/foot to keep the -3 dB point above 30 kHz. The calculator shows the actual roll-off curve based on your numbers.
How do I find my cable capacitance specification?
It is usually printed on the cable jacket or in the manufacturer datasheet, listed as picofarads per foot or per meter. Generic RCA cables are 30-50 pF/ft; high-capacitance cables can be 80+ pF/ft; specialty low-capacitance cables for phono use are 15-25 pF/ft.
Can cable capacitance affect digital signals like USB or HDMI?
Practically no for properly impedance-matched digital interfaces - the issue is reflection and ringing, not roll-off, and modern receivers re-clock the bitstream. The calculator targets analog applications where capacitance combines with source impedance to form a low-pass filter in the audio band.