How We Rate Amplifier Power: CTA-2006 at 1% THD+N

We are standardizing all published amplifier power numbers to the CTA-2006 method. This delivers comparable, repeatable, and honest results.

At a glance

  • Continuous RMS power at ≤1% THD+N.
  • All channels driven into non-inductive resistive loads of the rated impedance.
  • Automotive supply set to 14.4 V DC (+0/−5%) during the test.
  • Test tones: 1 kHz for full-range, 50 Hz for sub channels.
  • Must sustain the measured output for ≥15 s without exceeding 1% THD+N.
  • Distortion and noise measured over the 20 Hz–20 kHz band.

Why this matters

Power claims vary when methods vary. CTA-2006 defines the voltage, load, frequency, distortion limit, and duration. That prevents inflated “burst” numbers and makes different brands comparable.

Standard test conditions

Power & loading

  • Supply: 14.4 V DC, tolerance +0%/−5% (voltage monitored under load).
  • Loads: Non-inductive resistors within ±5% of rated Ω (e.g., 4 Ω = 3.81–4.20 Ω).
  • All channels driven: Identical signal to every channel type being rated.

Signal & setup

  • Tones: 1 kHz (full-range) or 50 Hz (sub-only). If a channel can’t reproduce these, use the center of its rated band.
  • Processing: Crossovers/EQ/bass boost off or flat.
  • Gain: Input sensitivity set to minimum (least sensitive).

Measurement procedure (continuous power @ ≤1% THD+N)

  1. Configure supply, loads, and cabling. Disable processing. Set gains to minimum.
  2. Feed the appropriate sine tone to all channels (1 kHz or 50 Hz).
  3. Increase input level until the amplifier output just reaches 1% THD+N (measured).
  4. Hold this level for at least 15 seconds. If the amp overheats, sags, or exceeds 1% THD+N, reduce level until stable for the full duration.
  5. Measure true-RMS output voltage per channel; compute power as P = V² / R. Report the lowest channel as the rating when channels differ.
  6. Repeat for other supported impedances or bridged modes (clearly labeled) if published.

THD+N specifics

  • THD+N includes harmonic distortion plus noise in the 20 Hz–20 kHz band.
  • 1% THD+N is approximately −40 dB relative to the fundamental.
  • For published “THD+N” specs, worst-case across the rated band is used at the stated power. We may also publish THD+N at 1 W/4 Ω for context.

Instrumentation

  • Audio analyzer / distortion analyzer capable of THD+N with ≥20 kHz bandwidth.
  • True-RMS voltmeter or analyzer voltage readout for VRMS.
  • Non-inductive resistor banks rated for the required power.
  • High-current 14.4 V DC supply with voltage monitoring under load.

How we will publish power

Our sheets and pages will use this format:

  • Continuous Power (CTA-2006): X W RMS × N @ Ω, ≤1% THD+N, 14.4 V, all channels driven.
  • Other loads: Additional continuous ratings at supported impedances, same criteria.
  • Bridged: Clearly labeled with load and conditions when applicable.
  • Optional: Dynamic Power via CTA-defined tone-burst method (1% THD+N), and Max Dynamic with 10% THD+N if used. These never replace the continuous rating.
  • S/N and THD+N: A-weighted S/N referenced to 1 W or rated power (noted), plus typical THD+N at 1 W for full-range amps.

Continuous vs. dynamic power

Metric Definition Use
Continuous (CTA-2006) Power at ≤1% THD+N for ≥15 s at 14.4 V, all channels driven. Primary rating. Directly comparable between products.
Dynamic (CTA-2006) Tone-burst peaks at ≤1% THD+N using CTA burst patterns (short on/off cycles). Optional. Illustrates short-term headroom. Not a replacement for continuous.
Max Dynamic Burst power allowing up to 10% THD+N. Optional. Marketing context only. Always labeled with 10% THD+N.

FAQ

Why 14.4 V?

It is the industry reference for a charging 12 V system. The +0/−5% tolerance avoids inflated numbers from over-volting.

Why 1% THD+N?

It sits just below obvious clipping and is achievable across product tiers. Using a fixed 1% limit makes ratings comparable.

Why all channels driven?

It loads the power supply and thermal system realistically. Single-channel ratings can exaggerate performance.

Will you still show burst numbers?

We may publish CTA-defined dynamic results for context. Continuous CTA-2006 remains the primary rating.

References

  1. ANSI/CTA-2006: Testing & Measurement Methods for In-Vehicle Audio Amplifiers (current revision).
  2. Audio Precision: “What are THD and THD+N?” (technical library).
  3. CTA overview and industry articles on CTA-2006 methodology.

Note: If an amplifier cannot meet 1% THD+N at the published load and voltage for ≥15 s, the measured distortion at the maximum sustainable level will be disclosed with the power figure.