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The Complete Phono Cable Guide: MM vs MC, Capacitance and Shielding
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posted by Vincent Zhang
Vinyl Audio
Published by IWISTAO
Capacitance, shielding, conductor materials, and connectors — everything that matters between your tonearm and phono stage
1. Why the Phono Cable Is Different
Most audio interconnects carry line-level signals in the range of 1–2 V RMS. A phono cable carries a signal from the cartridge that is between 100 and 1,000 times weaker — typically 0.2–5 mV for a Moving Magnet (MM) cartridge, and as low as 0.05–0.5 mV for a Moving Coil (MC) cartridge.
At these levels, every electrical characteristic of the cable has an audible consequence that would be entirely inaudible on a line-level connection. Two properties dominate:
- Capacitance — forms a resonant circuit with the cartridge's inductance. Too much capacitance causes a frequency-response peak in the upper treble (for MM cartridges).
- Shielding effectiveness — the signal is so small that even modest amounts of RFI or mains hum will degrade the signal-to-noise ratio.
These two factors — not conductor purity or cable geometry myths — are the engineering foundations of a good phono cable.
2. The Signal Chain and Voltage Levels
Figure 1 — The vinyl playback signal chain. The phono cable sits between the tonearm output and the phono preamplifier input, carrying the most vulnerable signal in the system.
Understanding where the phono cable sits in the chain clarifies why it demands special treatment:
| Stage | Typical Signal Level | Notes |
|---|---|---|
| MM Cartridge output | 1–10 mV RMS | Depends on modulation level and cartridge sensitivity |
| MC Cartridge output | 0.05–0.5 mV RMS | Some LOMC as low as 0.2 mV |
| Phono cable (this section) | Same as cartridge | No amplification; purely passive signal transfer |
| After phono stage (RIAA) | 150–250 mV RMS | RIAA EQ + ~40 dB gain (MM) or 60–70 dB (MC) |
| Line-level input | 1–2 V RMS | Standard consumer line level |
Because the phono cable carries an unamplified signal, any noise or distortion it introduces will be amplified along with the music — typically by 40–70 dB — before reaching the speaker. This is why noise introduced at this stage is so much more harmful than at any later point in the chain.
3. Cable Construction and Anatomy
Figure 2 — Cross-section of a typical phono cable showing the coaxial construction with signal conductor, dielectric insulation, shield, and outer jacket.
A phono cable is a twin-coaxial structure: two independent coaxial cables (one per channel) run in parallel from the tonearm output to the RCA connectors, plus a separate bare drain wire connected to the tonearm's ground tab at one end and to the phono stage's ground terminal at the other.
3.1 Signal Conductor
The central conductor carries the audio signal. It is typically solid-core or stranded fine-gauge copper or silver wire, ranging from AWG 26 to AWG 32. Smaller gauges reduce the physical stiffness of the cable — important because a stiff cable exerts torque on the tonearm, which can affect tracking.
3.2 Dielectric Insulation
The dielectric surrounds the conductor and determines the capacitance per unit length. This is arguably the most electrically important material choice. Lower permittivity (ε) means lower capacitance. Common dielectrics:
| Dielectric Material | Relative Permittivity (εr) | Typical pF/m | Comment |
|---|---|---|---|
| Air | 1.0 | ~11 | Ideal but impractical as sole insulator |
| PTFE (Teflon®) | 2.1 | 55–80 | Best practical choice; used in high-end cables |
| Polyethylene (PE) | 2.3 | 60–90 | Very good; used in quality cables |
| Polypropylene (PP) | 2.2 | 60–85 | Similar to PE, good performance |
| PVC | 3.5–6.0 | 100–200+ | Common in budget cables; high capacitance |
| Foam PE / Air–PE | 1.4–1.8 | 40–60 | Low capacitance; used in some broadcast cables |
Key rule: Choose PTFE or polyethylene insulation, not PVC, for the best capacitance performance.
3.3 Shield
The shield is a conductive layer surrounding the dielectric. It connects to ground (via the drain wire) and blocks RFI and EMI from reaching the signal conductor. Shield types include:
- Braided copper or silver-plated copper — coverage typically 85–97%; excellent mechanical durability; low DC resistance
- Foil (aluminium or copper/Mylar) — 100% coverage; good for high-frequency RFI; more fragile; usually used with a drain wire
- Combination braid + foil — highest noise rejection; used in professional and high-end phono cables
- Spiral/serve — flexible; moderate coverage; common in instrument cables
3.4 Outer Jacket
The outer jacket protects mechanically. For tonearm cables, flexibility matters more than durability — a stiff jacket can apply torque to the tonearm bearing. Soft PVC, polyurethane (PU), or silicone jackets are preferred.
3.5 Ground / Drain Wire
The separate bare or insulated ground wire connects the tonearm chassis to the phono stage's dedicated ground terminal. This is essential for hum cancellation. The ground wire should be continuous and have low DC resistance (< 1 Ω total).
4. Capacitance: The Most Critical Electrical Parameter
Follow the cartridge manufacturer’s recommended load capacitance (typically 100–300 pF depending on brand and model).
4.1 The LC Resonance Circuit
A Moving Magnet cartridge is an inductor with a significant inductance (typically 200–700 mH depending on cartridge design) and coil resistance (500–1,500 Ω). When connected to the phono stage, the total capacitance in the circuit (cable + phono stage input) forms a parallel LC resonant circuit with the cartridge inductance. The resonant frequency is:
f₀ = 1 / (2π × √(Lc × Ctotal))
f₀ = resonant frequency (Hz) · Lc = cartridge inductance (H) · Ctotal = total circuit capacitance (F)
If this resonance falls within the audible range (20 Hz–20 kHz), it creates a frequency response peak. The higher the capacitance, the lower the resonant frequency, and the more audible the peak becomes.
In real systems, the resonance is damped by the phono stage load resistance (typically 47 kΩ), limiting peak amplitude.
4.2 Example Calculation
For a typical MM cartridge with Lc = 500 mH:
At C = 200 pF: f₀ = 1 / (2π × √(0.5 × 200×10⁻¹²)) ≈ 15,900 Hz (just above audible range — acceptable) At C = 500 pF: f₀ = 1 / (2π × √(0.5 × 500×10⁻¹²)) ≈ 10,060 Hz (inside audible range — audible peak!) At C = 100 pF: f₀ = 1 / (2π × √(0.5 × 100×10⁻¹²)) ≈ 22,508 Hz (well above 20 kHz — ideal)
Lower capacitance pushes the resonance frequency higher, away from the audible range. This is the primary goal.
4.3 Why MC Cartridges Are Different
Moving Coil cartridges have extremely low inductance — typically 5 μH to 50 μH (three to five orders of magnitude less than MM). The resonant frequency for a MC cartridge at 500 pF total capacitance would be:
At L = 20 μH, C = 500 pF: f₀ = 1 / (2π × √(20×10⁻⁶ × 500×10⁻¹²)) ≈ 1,592,000 Hz (1.59 MHz)
Far above the audible range — capacitance has negligible effect within the audio band on MC cartridge frequency response.
Conclusion: Cable capacitance is a critical parameter for MM cartridges. For MC cartridges connected directly (not via step-up transformer), it is irrelevant. However, when an MC is used with a step-up transformer (SUT), the capacitance is reflected by the square of the turns ratio and can matter.
4.4 Typical Capacitance Values
| Component | Typical Capacitance | Notes |
|---|---|---|
| Tonearm internal wiring | 40–120 pF | Varies by arm design and wire length |
| Budget phono cable (1.2 m) | 150–300 pF | PVC insulation; high pF/m |
| Standard quality cable (1.2 m) | 80–150 pF | PE insulation |
| High-quality low-cap cable (1.2 m) | 40–80 pF | PTFE insulation |
| Phono stage input (typical) | 47–150 pF | Many vintage stages are higher |
| Target total maximum | ≤ 200–250 pF | Beyond this, peaks move into the audible range for high-inductance MM cartridges |
5. Conductor Materials — Facts and Myths
Figure 4 — Conductor material conductivity comparison and relative cost index. The conductivity difference between standard ETP copper and pure silver is approximately 6%, but the cost difference is over 12×.
The conductor material debate is one of the most contentious in audio. Here is an objective summary of the measurable facts:
| Material | Purity | Conductivity (% IACS) | Resistivity (Ω·m × 10⁻⁸) | DC Resistance (1 m, AWG 28) |
|---|---|---|---|---|
| ETP Copper (standard) | ~99.9% | 100% | 1.72 | ~0.21 Ω |
| OFC Copper (C10100) | 99.99% | 101.5% | 1.70 | ~0.21 Ω |
| OCC Copper (6N) | 99.9999% | 101.8% | 1.69 | ~0.21 Ω |
| Silver-plated OFC | OFC + Ag plate | ~105% | 1.63 | ~0.20 Ω |
| Pure Silver (Ag) | 99.99% | 106% | 1.59 | ~0.19 Ω |
5.1 Does Conductor Purity Matter?
From a pure resistance standpoint, the difference between standard ETP copper and pure silver is approximately 6% in resistivity. For a phono cable of 1.2 m at AWG 28, this translates to a DC resistance difference of roughly 0.02 Ω — completely negligible given that the phono stage input impedance is 47 kΩ. The voltage drop across the conductor resistance is immeasurably small.
Grain boundaries (which OFC/OCC seek to reduce) could theoretically affect signal transmission, but controlled double-blind listening tests have not consistently demonstrated audible differences between OFC and standard copper in blind conditions.
Objective assessment: The choice of copper purity has no measurable electrical effect on phono cable performance. Dielectric capacitance and shield effectiveness are the parameters that actually show up on instruments and correlate to listening results. Choose OFC if budget allows — it is a reasonable quality marker — but do not pay a large premium for OCC or pure silver expecting measured improvements.
5.2 Skin Effect at Audio Frequencies
Skin depth in copper at 20 kHz is approximately 0.46 mm. Since phono cables use very fine conductors (AWG 26–32, diameter 0.13–0.40 mm), the conductor is smaller than the skin depth even at 20 kHz. Skin effect is therefore negligible in phono cables operating in the audio band.
Skin depth δ = √(2ρ / ωμ) At 20 kHz in copper: δ = √(2 × 1.72×10⁻⁸ / (2π × 20,000 × 4π×10⁻⁷)) ≈ 0.46 mm
Skin effect becomes relevant only when conductor radius exceeds skin depth.
AWG 28 conductor diameter = 0.32 mm — smaller than δ, so skin effect is negligible in the audio band.
6. Shielding, Grounding, and Noise Rejection
Because the phono signal is measured in microvolts, shielding is essential. The threats are:
- Mains hum (50/60 Hz and harmonics) — from transformers, power wiring, fluorescent lights
- RFI (radio frequency interference) — from Wi-Fi, mobile phones, switching power supplies
- Electrostatic coupling — from high-voltage sources near the cable
6.1 Shield Coverage and Transfer Impedance
Shield effectiveness is characterised by transfer impedance ZT (Ω/m) — the lower, the better. For low-frequency noise (mains hum), coverage percentage is the dominant factor. For high-frequency RFI, both coverage and shield conductance matter.
| Shield Type | Coverage | Low-Freq. Rejection | HF RFI Rejection | Flexibility |
|---|---|---|---|---|
| Single braid (90% coverage) | ~90% | Good | Good | Good |
| Double braid | ~97% | Excellent | Excellent | Moderate |
| Foil + drain wire | 100% | Good (thin foil) | Very Good | Poor |
| Braid + foil combination | 100% | Excellent | Excellent | Moderate |
| Spiral/serve | 85–92% | Moderate | Moderate | Excellent |
6.2 Grounding the Shield — One End or Both?
Depending on system grounding topology, shields may be grounded at one or both ends. Many commercial phono cables use both-end grounding, while some designs use single-end grounding to reduce ground loops.
Ground loop warning: If you hear a persistent 50 or 60 Hz hum, the most common cause is a ground loop. Verify that the tonearm's ground wire connects to the phono stage's ground terminal, and that both RCA shields do not also connect to the same ground at the source end.
6.3 The Ground Wire
Almost all phono cables include a separate bare or insulated conductor — the ground wire — that connects the turntable/tonearm chassis to the phono stage's ground lug. This wire should:
- Have low resistance (24–26 AWG is sufficient; shorter is better)
- Make solid contact at both ends (spade lug or stripped end)
- Not be substituted by relying on the RCA shield connection alone
7. Connector Types
Figure 5 — The three main connector types used in phono cables: RCA, 5-pin DIN, and XLR (balanced).
7.1 RCA (Phono Plug)
The standard for most consumer turntables. The RCA plug carries signal on the centre pin and ground on the outer barrel. Quality RCA connectors feature:
- Gold, rhodium, or silver plating (reduces oxidation at the contact point)
- Tight, low-resistance barrel-to-chassis contact
- Solid or chunky barrel body (avoids microphony from vibration)
- Cold-weld or screw-down cable attachment (solder quality matters)
Common connector brands used in quality phono cables: Switchcraft, Neutrik, WBT, Cardas, Furutech.
7.2 5-Pin DIN (IEC 60130-9)
Used primarily by Linn, Rega, SME, and some German manufacturers. The 5-pin DIN connector carries both channels and ground with separate signal-return pins per channel, which can slightly reduce crosstalk. Pin assignment (standard phono DIN):
| Pin | Signal |
|---|---|
| 1 | Left channel signal (+) |
| 2 | Ground / shield |
| 3 | Right channel signal (+) |
| 4 | Left channel return (−) |
| 5 | Right channel return (−) |
DIN cables for Rega turntables typically run DIN at the turntable end and RCA at the phono stage end. Ensure the connector locks securely — a loose DIN connection is a common source of intermittent hum.
7.3 XLR (Balanced)
A small number of high-end turntables (e.g., certain Brinkmann, Clearaudio, and custom-built designs) offer balanced XLR outputs. A balanced connection carries the signal as a differential pair (signal+ and signal−), which provides Common Mode Rejection Ratio (CMRR) noise cancellation:
CMRR (dB) = 20 × log₁₀(V_differential / V_common_mode)
A good balanced connection achieves CMRR > 60 dB, meaning common-mode noise (hum, RFI) is reduced by a factor of 1,000 or more.
Balanced phono connections require a phono stage with balanced inputs. They offer the best noise rejection in difficult electrical environments.
8. Building Your Capacitance Budget
Figure 6 — Total capacitance budget for four representative setups. Keep the sum of tonearm wiring + cable + phono stage input capacitance below 200 pF for flat MM cartridge response.
8.1 How to Measure Your System's Capacitance
Total system capacitance requires measuring three contributions:
- Tonearm internal wiring — specified in the tonearm manual, or measure with an LCR meter at the tonearm output plug with the cartridge disconnected.
- Phono cable — measure with an LCR meter, or check the manufacturer's datasheet (usually quoted as pF/metre).
- Phono stage input capacitance — specified in the manual, or measure at the RCA input with the cable disconnected.
C_total = C_tonearm + C_cable + C_phono_input
Follow the cartridge manufacturer’s recommended load capacitance (typically 100–300 pF depending on brand and model).
8.2 Adjusting the Budget
If your measured total exceeds 200–250 pF:
- Replace the phono cable with a low-capacitance alternative (easiest and most effective step)
- Use a shorter cable — if the phono stage is close to the turntable, a 0.6 m cable has half the capacitance of a 1.2 m cable
- Select a phono stage with lower input capacitance — some stages allow the user to select input capacitance via DIP switches or plug-in capacitors
- Select a cartridge with lower inductance — lower-inductance MM cartridges are less sensitive to capacitive loading
Practical tip: Many mid-price phono stages have input capacitance of 100–150 pF. Combined with a tonearm wiring contribution of 80–100 pF, this already uses up a significant portion of the 200 pF budget before any cable is connected. In this case, a cable with pF/m ≤ 50 pF/m (PTFE insulated) at 1.0–1.2 m length keeps the total below the threshold.
9. Buying Guide: What to Look for
| Priority | Parameter | Target Value | Where to Find |
|---|---|---|---|
| 1 (Critical) | Total capacitance per metre | < 80 pF/m (PTFE/PE) < 50 pF/m (best) |
Manufacturer datasheet |
| 2 (Critical) | Shield coverage | > 90% braid or foil+braid | Product description |
| 3 (Important) | Separate ground wire | Yes, with spade/bare end | Physical inspection |
| 4 (Important) | Jacket flexibility | Soft PVC, PU, or silicone | Physical inspection |
| 5 (Useful) | Connector quality | Gold/rhodium plated, tight fit | Brand (Switchcraft, Neutrik, WBT) |
| 6 (Optional) | Conductor material | OFC minimum; OCC/silver optional | Manufacturer spec |
9.1 Length Considerations
The optimal cable length places the phono stage close to the turntable. Every 0.3 m adds roughly 15–25 pF (for a quality cable). Practical considerations:
- 0.6–1.0 m: Ideal if the phono stage is adjacent to or inside the rack
- 1.2–1.5 m: Standard; suitable for most installations
- > 1.5 m: Use only if unavoidable; verify total capacitance; consider a phono stage with adjustable input capacitance
9.2 Notable Commercially Available Low-Capacitance Cables
| Cable / Brand | Capacitance | Shielding | Notes |
|---|---|---|---|
| Belden 1505F (BJC LC-1) | ~40 pF/m (12 pF/ft) | Double braid | Exceptional value; used by Blue Jeans Cable |
| Canare L-4E6S | ~64 pF/m | Spiral + braid | Star-quad; excellent noise rejection |
| Mogami 2534 | ~62 pF/m | Braid + foil | Industry standard; studio-grade |
| Cardas Neutral Reference | ~54 pF/m | Multi-layer braid | High-end; matched conductor geometry |
| Ortofon 6NX-TSW 1010 | ~47 pF/m | Silver-plated braid | Made for phono use; 6N OFC conductor |
| Audience Au24 SX Phono | < 20 pF/m | Full braid | Ultra-low-cap; high-end pricing |
10. DIY Phono Cable: Materials and Construction Tips
Building a phono cable is well within the skill of any hobbyist with basic soldering skills. The key advantages are control over capacitance, conductor material, connector quality, and exact length.
10.1 Recommended Wire
- Belden 1505F — ~40 pF/m; double braid; excellent low-cap choice for DIY
- Mogami 2799 — ~43 pF/m; purpose-designed phono cable; PTFE insulation
- Van Damme 268-500-000 — ~56 pF/m; PTFE; flexible jacket; good value
- Any miniature coaxial with PTFE insulation and > 90% braid coverage, specifying < 80 pF/m
10.2 Recommended Connectors
- Switchcraft 3502AU — gold-plated; solid chassis; widely available; excellent value
- Neutrik NYS373 — compact; solid; reliable; used in professional studios
- WBT-0144 Ag — premium; silver alloy; low contact resistance
- Furutech FP-126(G) — rhodium or gold plated; audiophile-grade
10.3 Soldering Tips for Phono Cables
- Use 60/40 or 63/37 tin-lead solder, or a quality lead-free (SAC305). Avoid excessive flux.
- Strip the outer jacket only 25–30 mm from the end to minimise unshielded length.
- Tin the shield braid before folding it back — this prevents stray strands from touching the centre conductor.
- Ground the shield at the phono stage end only. At the tonearm end, leave the shield floating (only the drain wire should contact ground).
- Keep the soldering iron on the connector pin for the minimum time necessary — heat conducted into the connector body can damage the dielectric of the cable.
- After assembly, test with an LCR meter: measure capacitance between signal pin and ground. Compare to the cable's rated specification × length.
11. Common Myths Addressed Objectively
| Claim | Objective Assessment |
|---|---|
| "Pure silver cables sound better" | Silver has ~6% higher conductivity than OFC copper. At the resistances involved in a 1.2 m phono cable (≈ 0.2 Ω), this is unmeasurable. No controlled double-blind test has demonstrated consistent audible difference. |
| "Cables need break-in / burn-in time" | No credible physical mechanism supports this for metallic conductors. Measured electrical parameters do not change after initial settling of mechanical stress in connectors. Subjective impressions of "break-in" are likely auditory adaptation. |
| "Directionality matters in cables" | Copper and silver are not rectifiers. Electrical signals travel equally in both directions. Cable directionality has no physical basis for non-semiconductor conductors. |
| "More expensive cables always perform better" | False. A $25 Belden 1505F cable measures better in capacitance than many cables costing $500+. Price reflects materials cost, brand premium, and marketing — not necessarily measured electrical performance. |
| "Cable capacitance doesn't matter for MC cartridges" | Largely true for direct MC connections (see Section 4.3). However, when using a step-up transformer, the reflected capacitance can matter — check the SUT specifications. |
| "Star-quad cables reduce noise" | True, but only when using balanced connections. In unbalanced RCA connections, star-quad geometry does not provide differential noise rejection. Its main benefit in unbalanced use is improved magnetic field rejection from the geometric cancellation of induced noise. |
12. Conclusion
The phono cable occupies the most electrically vulnerable position in the vinyl playback chain. Its performance is determined by two parameters above all others: capacitance (critical for MM cartridges) and shielding effectiveness (critical for noise rejection in all systems).
For a MM-based system, keeping the total system capacitance below 200–250 pF is the single most important electrical design criterion. This requires selecting a cable with PTFE or PE insulation, measuring the contribution from tonearm wiring and phono stage input capacitance, and choosing cable length accordingly.
For conductor material: quality OFC copper is entirely adequate for measured performance. The marginal conductivity improvements of OCC copper or pure silver cannot be detected by instruments under normal phono cable conditions, and claims of consistent audible improvement have not been validated in controlled listening tests. Invest your budget in low-capacitance construction and quality connectors rather than exotic metals.
A correctly specified phono cable — low capacitance, well shielded, with a secure ground connection — can be built or purchased for modest cost and will match or exceed the measurable performance of far more expensive alternatives.
Find More
The Complete Guide to Vinyl Phono Tonearms: Design, Geometry and Setup The Complete Guide to Phono Preamps: Unlocking the Full Potential of Your Vinyl Collection Inside the Phono Cartridge: Why MM and MC Use Different Generator Designs — and Often Sound Different Learn more about phono stage amplifier IWISTAO Discrete Components MM/MC Phono Stage FET Amplifier for LP Phono Split-type AC110V/220V HIFI AudioReferences
- Elliott, R. (2011, updated 2020). Magnetic Phono Pickup Cartridges — Cartridge Loading. Elliott Sound Products. https://sound-au.com/articles/cartridge-loading.html
- Hagerman, J. Cartridge Loading. Hagerman Technology LLC. https://www.hagtech.com/loading.html
- IEC 60098 (2022). Analogue audio disk records and reproducing equipment. International Electrotechnical Commission.
- IEC 60130-9. Connectors for frequencies below 3 MHz — Part 9: DIN connectors. International Electrotechnical Commission.
- Belden Inc. 1505F Datasheet — Coaxial Cable Specifications. https://www.belden.com
- Blue Jeans Cable. Hum Rejection in Unbalanced Audio Cables. https://www.bluejeanscable.com/articles/humrejection.htm
- Mogami Wire & Cable. 2534 and 2799 Phono Cable Datasheets. https://www.mogamicable.com
- Ortofon A/S. 6NX-TSW 1010 Phono Cable Specification. https://www.ortofon.com
- Audio Science Review Forum. (2023). How to measure capacitance on a tonearm and phono input. ASR Forum Thread
- The Vinyl Verdict. (2024). The Impact of Cartridge Loading on Sound. https://thevinylverdict.com/the-impact-of-cartridge-loading-on-sound/
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