Wamp 2.5 mkii class D digital integrated amplifier

Excerpts of Waversa systems W AMP2.5 review by: gimgwanmyeong with translation and corrections for clarity.

 

6 types of speakers were used during this review including Waves Monitor 30.1, Dynaudio Contour S 1.4 LE, Joseph Audio Pulsar, Odeon Orfeo, PMC fact.3, Stenheim Alumine 2way, and Waver's W DAC3 To be taken over. I also listened to the ATC 100 SL tower, which is said to be the touch of the hi-fi club hall.

 

Class D amplifier vs digital amplifier

 

In order to distinguish the concept between class D amplifier and digital amplifier, it is necessary to understand PCM and PWM.

 

PCM (Pulse Code Modulation)

 

PCM is a method of converting analog signals into digital signals and assigning digital values representing each analog signal. In short, PCM is an analog signal expressed as a digital value at the position of each pulse. For example, CDs contain 16-bit, 44.1kHz PCM digital data. That is, in the case of an analog signal that has been processed for 1 second, the PCM recognizes the analog signal as a pulse having different heights (vertical axis) of 4,5536 (16 bits) at 44,100 points (horizontal axis).

 

PWM (Pulse Code Modulation)

 

PWM is a method of converting analog signals into digital signals and also means digital values representing each analog signal. In short, PWM is the analog signal expressed as a digital value by the width of each pulse. While PCM is the height of the pulse as viewed from the scale (time) of the horizontal axis, PWM is the width of the pulse as viewed from the height of the constant pulse (0 and 1). The upper part (1) of each pulse of PWM represents the 0 ~ 180 degree part of the sine wave (analog signal), and the lower part (0) of the sine wave represents the 180 ~ 360 degree part of the sine wave, and with the higher the analog signal (Amplitude) comes a proportionate widening of the sine wave..

 

Class D amplifier

 

As one of the amplifier amplification methods, D does not refer to 'D' of digital, but only the order following class A, class B, class AB, and class C. Usually, after converting the analog signal to PWM (this device is a Triangle Wave Generator), instead of analog amplifying elements such as transistors or vacuum tubes, it is amplified through a switching controller and an output stage. Therefore, the class D amplification method that amplifies by varying the switching time according to the width of the PWM signal is also called switching amplification in the United States. In any case, the switching amplified digital signal is converted back to an analog signal through a low pass filter and passed to the speaker.

 

Digital amplifier = The concept of using a PWM signal rather than an analog signal when a Class D amplifier amplifies, but a digital amplifier refers to an amplifier that consists of both digital parts as well as amplification. In the case of W AMP2.5, all the input analog signals are converted into PCM, which is a digital signal through an AD converter, and a high-performance chip called WAP (Waversa Audio Processor) converts PCM back to PWM in the process of performing digital calculations and algorithms.  This processing improves sound quality, secures linear frequency band characteristics, and increases resolution through mathematical calculations made on a chip instead of analog devices such as resistors and coupling capacitors.

 

So, how is Waversa AMP 2.5 different from existing amplifiers?

 

1. The analog signal is converted to a digital signal PCM (24 bit, 176.4 kHz) by AD conversion. It is the starting point of all digital processing and the most significant difference from the existing Class D amplifier that converts the analog signal directly into PWM. to be.  The Waversa Audio Processor converts the analog signal to PCM, up-sampling from 16 bits to 24 bits and 44.1 kHz to 176.4 kHz appears to be a stepping stone to maximize resolution before further processing (@705.6 kHz or 768 kHz if 48 kHz source or multiple thereof). The frequency response characteristic of W AMP2.5 is 0 to 160 kHz wideband, which seems to be due to the initial upsampling.

 

2. Uniformly align the time axis of the PCM through the WAP chip: The Triangular Wave Generator used to make PWM has an inherent limitation since the PWM does not have a clock on its own.  The WAP chip uniformly aligns the time interval of the PCM with a high-precision clock in advance then converts to PWM. The PWM signal is then passed through the Class D amplification process to the final analog output stage.

 

3. Improve linearity and resolution through WAP chip: According to Waversa, it secures linear response characteristics and increases resolution extremely through mathematical calculation.  These algorithms perform in real time on WAP chips. The mid-range boost problem, which is the biggest drawback of analog amplifiers, has been solved through the WAP chip. The harmonic characteristics created by the WAP chip presents a Class A sound.

 

4. Various digital corrections are also made on the WAP chip to improve detail and imaging regardless of volume, which are a unique advantage of digital amplifiers. There are three major digital corrections that Waversa has proposed:

 

A. WS (Waversa Ultra Sound) mode: It is said that the resolution, sound stage, and air sensation can be made differently using the unique signal processing algorithm of the WAP chip, but the user can select three modes.

 

B. AC (Ambient Control) mode: After detecting ground noise and vibration inside and outside the amplifier through a sensor, the concept is that the WAP chip generates and cancels the same value of noise in real time through digital calculation. There are five levels of mode, from 'NO', which accepts noise as it is, to 'MAX', which completely eliminates noise.

 

C: A tube harmonic algorithm reconstructs the 2nd, 4th and 8th harmonics of real music that were lost during digital recording or digitization of master recordings. This is how digital music sounds poignantly real, spatially diversified and natural.

 

5. Reduced output amplification and subsequently amplification error by one-fourth through four parallel balanced transformerless (PBTL): Class D 600W output at 4 ohms by adopting a parallel structure of normal, reversed, normal, and reversed phase, which is twice the normal BTL. The dual-mono design with the left and right channels completely separated is allowed using this BTL structure. If you look at the inside picture, you can see that the toroidal transformer and the SMPS power source are also covered with duralumin blocks, respectively, and are installed in pairs of 2 for each channel.

 

 * PBTL = Para Bridge-Tied Load. PBTL comprises several small output amplifiers that are combined to form one amplifier. Configured in this way, it has an extremely low impedance and can even drive loudspeakers with low efficiency.

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