What kind of power amplifier could be “perfect”? It should amplify the audio signal without any distortion and could offer profuse power to drive speakers at the same time. Any power amplifier with low distortion, low noise and high output could match the requests described above, no matter it’s heavy or not , or it’s heat or not. The ICEpower power module which being used in Murano P-1000S plus and P-500S plus has the most advanced technology for audio signal amplification and could offer the more lifelike music enjoyment for music lovers.

In fact, there is no pretty much innovations for the traditional power amplifier designing during the past decades, but Class-D (or Pulse width modulation, PWM) amplification made a mighty advance at the same period due to the trend of smaller size, less power consumption and environmental consciousness. The ICEpower Module of Bang & Olufsen ICEpower a/s is one of the few PWM power modules which have Hi-End audio performance in mind. ICEpower technology aims to revolutionize efficiency of the entire audio amplification chain, from the audio power supply, audio amplifier to the audio transducer - what we call the complete audio power conversion path. In other words, ICEpower technology offers the best of two worlds, ultra efficiency and high audio quality.

Regarding the work flow path of traditional Class-D / PWM amplification, you should convert the linear analog audio signal to PWM signal first, and then amplifying it and then restore to analog audio signal by passing it through LPF (low-pass filter). The major problems which made the traditional PWM amplifier sounds not good happened during the first and last transform processes. For the first process part, when transferring the linear analog audio signal to PWM signal, it should compare the input signal with the sawtooth wave generated by PWM amplifier. The higher high frequency response needs higher sawtooth wave frequency. For example, the sawtooth wave frequency should be higher than 1MHz if you asked the audio response frequency to reach 20kHz, but too high sawtooth wave frequency also will cause EMI problems. In addition, the PWM conversion is on the basis of the sawtooth waveform. The transferred PWM waveform would be distortion if the reference sawtooth waveform was not accurate enough.

And what’s the problem on the last process part that LPF would cause? Most PWM amplifiers use MOSFET component to control the current output level at the end of circuit, but MOSFET has to combine LPF to restore the PWM square wave to audio sine wave and then drive the speakers. The major problem with LPF is being combined with inductances and capacitances. When the current flow pass through the inductances inside LPF, the magnetization curve is non-linear and combined with the impedance variation of the speakers for different frequencies would cause audio single being distorted. Since both the sawtooth waveform generator and LPF are indispensable components for traditional PWM amplifier, it seems it’s impossible to break the difficulty, but B&O ICEpower a/s indeed gave us the solution with creative thinking and technologies called Control Oscillation Modulation (COM) and Multivariable Enhanced Cascade Control (MECC).

The COM of ICEpower is similar with the Pulse Amplitude Modulation (PAM) that sampling input signal waveform with equal dwell time and module into square waveform with different amplitudes of vibration, i.e. PAM signal. After that, ICEpower interchange the x-axis and y-axis and transform the waveform into vibrational density square waveform with same amplitude, i.e. PWM signal! With this unique trick, ICEpower removes the sawtooth wave generator of traditional PWM amplifier and offers more accurate, less distorted PWM modulation.With regard to the MECC, ICEpower gets out test signals before and after LPF and then send them to the input end of PWM modulation for comparing and correcting. ICEpower greatly reduces the distortion of the LPF.

（Some major figures and information in this article come from Bang & Olufsen ICEpower a/s official web site： http://www.icepower.bang-olufsen.com）