Amplifier Class Comparison
| Parameter | Class A | Class AB | Class D |
|---|---|---|---|
| Efficiency | ~25% | ~60% | ~90% |
| Heat | High | Moderate | Low |
| Sound Character | Warm, sweet, natural midrange | Balanced, clean, powerful | Clean, neutral, analytical |
| Harmonic Profile | Dominantly even-order | Mixed | Very low, odd-order dominant |
| Best For | Vocal/jazz, small rooms | All-around, living rooms | Desktop, portable, subwoofers |
| TRASAM Examples | AA3PRO, AA2PRO | A12 PURE, A12PRO, A11PRO | HD200 headphone amp |
Class A — The Purity Approach
In Class A, the output transistors conduct continuously — even with zero input signal, they’re consuming full power. This means the transistor never crosses the “off” threshold, eliminating crossover distortion entirely. The trade-off: ~25% efficiency, significant heat, and high cost per watt.
TRASAM AA3PRO (220W×2 Class A) uses 24 Sanken transistors with dual O-core transformers — a configuration typically found in amplifiers costing $3,000+. The AA2PRO (165W×2 Class A) offers warmer, sweeter midrange at a lower power level.
Class AB — The Practical Compromise
Class AB runs in Class A at low power (for purity) and switches to Class B at high power (for efficiency). This gives the best of both worlds: clean low-level detail with power headroom for dynamic peaks. Most TRASAM amplifiers use this architecture with proprietary circuit innovations (Honeycomb Symmetry, Diamond fully-balanced, PureSound voltage modules).
When to Choose Each
- Choose Class A if: sound quality is the only priority, room is well-ventilated, listening at moderate volumes, budget allows higher cost per watt
- Choose Class AB if: large room, need high power, want all-around versatility without compromising too much on purity
- Choose Class D if: space is limited, power efficiency matters, using for desktop or portable applications