Understanding Amplifier Gain Overlap and Test Tone Loudness
Setting amplifier gain isn't just about avoiding clipping—it's also about getting the most usable power from your system. That depends heavily on the loudness of the test tone you use and how much overlap you allow between tone and real-world signal peaks.
What is Test Tone Loudness?
Test tones are digital sine waves at fixed levels:
- 0 dBFS: Full-scale (maximum) digital signal
- -5 dBFS: 5 dB below max—matches loud music peaks
- -10 dBFS: 10 dB below max—represents average playback level
What is Overlap?
Overlap is the difference between your test tone level and the maximum signal your source unit can send. More overlap = louder output, but also higher distortion risk.
- -5 dB tone = 5 dB overlap
- -10 dB tone = 10 dB overlap
How It Affects Output
Lower tone levels (more overlap) make the system louder during music playback—but also more likely to clip during transients.
| Test Tone Level | Gain Position | Risk | Use Case |
|---|---|---|---|
| 0 dB | Low | Very Low | Sound Quality / Mids & Highs |
| -5 dB | Mid | Moderate | Daily Loud Bass |
| -10 dB | High | High | SPL / Max Output Builds |
Best Practice by System
- Sound Quality (SQ): Use 0 to -2 dB tones
- Daily Bass / Demo Builds: Use -4 to -6 dB tones
- SPL / Max Output: Use -8 to -10 dB tones, but monitor clipping carefully
Final Tips
Start conservative, especially on mids and highs. For subs, -5 dB is usually safe and loud. Always check for clipping using an oscilloscope, distortion detector, or a tool like the JL Audio MAX or DD-1+.