In audio amplifiers designed for natural music reproduction, dynamic characteristics that respond to quickly changing music signals and flat phase characteristics are more important than simply improving static specifications. To achieve this, we need to focus on the amplifier's raw performance before applying Negative Feedback (NFB).
The LHIH A200 amplifier uses a wide-band, small-capacity bipolar transistor for the voltage amplification stage. By significantly improving the raw performance (open-loop frequency response) to 500KHz (-3dB) compared to traditional methods, and minimizing NFB, it achieves a substantial improvement in dynamic characteristics and flat phase characteristics. This results in a lively and genuine music reproduction experience.
Low NFB High-Speed Voltage Amplification Stage
The volume control circuit, a crucial factor in sound quality, employs a current drive low-impedance volume control that eliminates signal currents passing through carbon resistors or sliding contacts. This minimizes sound quality degradation and significantly enhances the quality compared to conventional methods.
Separate winding, separate rectification high-speed power supply
For the energy source, a high-capacity 260VA EI core transformer with excellent transient response is used in the power supply section. By employing separate windings and rectification, stability is enhanced against fluctuations. Furthermore, multiple custom electrolytic capacitors using low-loss foil are connected in parallel to achieve low impedance and high-speed characteristics. A 2.0mm diameter OFC bus bar is used in the power ground to obtain a clear ground potential.
Highly resilient copper-plated shielded chassis
The top cover is made of 1.6mm thick iron plate, while the bottom chassis is made of 2.0mm thick copper-plated iron plate to enhance rigidity. The heat sink employs a vibration-resistant chimney type, connected to the top cover and bottom chassis, further increasing rigidity. Together with the three-point support system using sintered alloy-made heavy-weight legs (choice of point or surface grounding), this design achieves excellent anti-vibration characteristics.
Beyond Class High-Grade Parts
To achieve high-fidelity reproduction, we carefully selected parts with minimal coloration and information loss. These include 1% metal film resistors, high voltage audio electrolytic capacitors, and silver-dipped mica capacitors, ensuring that both the circuit and components are of the same high quality as the advanced LHH A700 amplifier. We also used high-reliability components like brass-machined high-grade RCA pin jacks and banana plug-compatible vice-type speaker terminals, as well as gold-plated contact relays to support stable and reliable music reproduction.
Interface Control Function for Optimal Music Reproduction
When connecting the amplifier to CD players, speakers, or the listening room, you may encounter the need for subtle tuning to match the various usage conditions. In the past, this involved tone control functions that could inevitably lead to a decrease in audio quality or required solving problems through settings or cable selection.
However, the LHH A200 offers a wide range of adaptability to various usage conditions through input impedance switching and NFB control. These controls allow delicate adjustments to bring out the nuances and expressions of music performances, including subtle changes in breath and dynamics. The settings change the operating state of the amplifier circuitry and do not introduce any quality degradation similar to traditional tone controls. This reflects our simple and straightforward design philosophy.
The input impedance can be selected from three positions: LOW (10kΩ), MID (15kΩ), and HIGH (20kΩ). As you move from LOW to HIGH, the sound quality tends to shift from sharp to mild.
NFB control allows you to switch the amount of Negative Feedback, with three positions available: LOW (20dB), MID (23dB), and HIGH (26dB). As you move from LOW to HIGH, the sound quality tends to change from open and expansive to a more stable and settled direction.
With these nine interface control settings, you can achieve the best music reproduction in various listening environments.
Fig 1: [Frequency Response of Conventional Amplifiers]
Due to stringent phase compensation required to apply heavy NFB, the raw performance before applying NFB attenuates within the audible range. As a result, NFB levels in the audible range are not constant, leading to different distortions and phase characteristics across frequencies.
Fig 2: [Frequency Response of LHHA200]
Since the raw performance extends far beyond the audible range, NFB levels within the audible range remain constant, resulting in consistent distortion across frequencies. The phase characteristics, which influence soundstage and imaging, become flat, leading to improved transient response.