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Technology

How the Maestro Amplifiers work.

The Maestro True Digital Amplifiers use a novel technology to deliver 'digital sound' signals to your loud speakers.  Unlike regular amplifiers the Maestro is a single box, replacing the traditional DAC > Pre-Amp > Power Amp boxes.  

It can all get a little too technical, but for those who 'really need to know', we've put together a brief description below.  There are 3 core stages that the incoming digital stream is processed through - and it's not until the final stage that it becomes 'analog' - and it's this feature amongst others that keeps the music 'true'.

 

Modulator

The technology used in the Maestro-50 is based on a pulse-code-modulated (PCM) to pulse-width-modulated (PWM) converter called a modulator.

The modulator receives the audio in PCM (I2S) 16-24-bit audio format with a sample rate depending on the input. In a PCM signal format each sample has a assigned amplitude, see below (left side). PWM format signal (right side) has the magnitude for each sample described as a width as oppose to a height in PCM signal. The signal is up-sampled eight times internally (e.g. 8 x 48kHz = 384kHz) and then the modulator converts the signal to PWM with 384kHz switching frequency.

The sample rate is 44.1kHz. The amplifier selects automatically the sample rate and can run with up to 96kHz. No up or re-sampling is used.

To compare, a CD-player uses 44.1kHz and DVD-player 48kHz. CD/DVD players that specify higher sample rates are using up-sampling. The amplifier accepts digital audio input with a maximum audio sample word length of 24-bits.

The modulator also has built in digital audio processing which is used in the Maestro-50 for sub-woofer processing.


Power stage

The PWM signals for each channel is connected to the inputs of the power stage, where the PWM signals are internally level shifted and fed into two sets of N-channel DMOS power transistors. The power stage is designed in a stereo Bridge-Tied-Load (BTL / full H-bridge) configuration, using a ½ H-bridge (one set of transistors) for each of the four speaker connections.


Passive LC low-pass filter (just prior to speaker terminals)

The PWM output from the power stage filtered just before the speaker terminals using a second order LC low-pass filter. In this stage the 384KHz PWM signal is removed, leaving only the Low Frequency (analog). This is where the signal, for the first time, becomes analog. 

 

How it connects

The Maestro-50 sits between your loud speakers and your digital music source.  Simply plug in the power (Universal 110-240VAC 50-60Hz) cable and your digital audio source, via Optical S/PDIF or COAX S/PDIF - then connect your left and right speakers to the speaker terminals and you're ready to go.  Optionally you can also connect a powered Sub woofer.
 

The completed solution

All of the above is carefully contained within a solid aluminium chassis - along side a specially selected power supply (which normally is used in the medical industry). The result is a very high quality, carefully engineered True Digital Amplifier that not only sounds good, but looks great too.

Below is the Maestro-50 (CAD outline)

 



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