mhz class-d amp for hifi audio

General Description

MCD stands for "MHz Class-D", a new branch of Class-D amplifier technology created by John Fu (Fumac) and Zhaolian Fu. This Class D amplifier technology operates at a relatively higher sampling frequency between 700kHz and 2.6MHz(factory selected).
This technology allows one to design amplifiers with excellent specification:
- High output power (up to 800w or higher),
- Very Low THD at full audio frequency (<0.00x%)
- Bandwidth 0-150kHz
- Small phase-shift
- Producing a Class-A alike sound.
All of these features can be achieved in a compact, cool running and environmental friendly circuitry. The superior sound quality suitable for wide variety of demanding applications.

Applications include:
1. HiFi audio
2. Active speaker
3. Professional amplifier
4. AV system
5. Ultrasonic high power AMP

MCD amplifier features two feedback paths (Figure 1). One is to produce the high frequency oscillation. The other is for audio frequency (AF) error feedback. This AF feedback includes the output filter to ensure load independent performance. By combining these two loops, One can create a system with both exceptional audio performance and technical indicators.

AF Error Feedback , Low THD
MCD has an audio frequency error feedback directly from the speaker terminal. This feedback can compensate distortion generated by the filter, so MCD can obtain a very low THD together with a very high power output.

The Higher The Sampling frequency ,
The More Detail
Previously, Class D technology ran below 100kHz. It was not fast enough for full-range (10Hz~20KHz) audio performance and most likely it was suitable for subwoofer (10Hz to 250Hz) applications only.
More recently, some Class D designers were able to increase the switching frequency to 200kHz-250kHz. This type of Class D amplifiers can produce close to audio full range (about 10hz-18KHz). Typically, these designs have great bass but poor treble. This kind of amplifiers can be found in home AV systems, sub-woofers, and medium class audio applications.
Bringing us up to date, there are some very good designs running at frequency in range 350kHz - 450KHz. Those are the very first designs that can reproduce the acceptable "full bandwidth" (10Hz~22kHz) with finesse.However, the large phase shift between bass and treble was a disadvantage in reproducing cohesive sound.
MCD runs at frequency between 700KHz to 2.6MHz (up to 6 times faster than other current technologies). It extends the amplifier bandwidth from below 1Hz to beyond 100KHz with a simple filter (150kHz Low Pass Filter). The high switching frequency makes all this possible.

The MCD will generate lower EMI, has lesser phase shift and a wider bandwidth than other Class-D amplifiers.