Just another amplifier also in progress ... 😀 same schematic but dual layer PCB
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Some pictures of my amplifier build. The basis of this amplifier is formed by two ExtremA amplifiers: http://www.diyaudio.com/forums/solid-state/96853-extrema-class-strikes-back.html
But these class-a amps generate a lot of heat resulting in big heatsinks and housings.
Because the ExtremA is a balanced amplifier design that has also separate powersupplies for the driver and powerstages, I had the possibility to add a way to regulate the voltage of the powerstage according to the level of music that must be played. Bias currents and gain are not affected by doing this. This is done completely in the digital domain.
SPDIF is taken in and converted to I2S and then fed to a big PIC32MZ controller that now checks for the peak level of the waveform and adjusts the buck converts by PWM to create the exact voltage needed for the level of sound. The audio is delayed just a little bit to make sure that the voltage is on the powerstage and stable just before the audio arrives at them.
From the PIC32 the audio goes to a DF1706 and four PCM1704 to convert the digital audio to analog and then feeding it to the two ExtremA amplifiers.
I have done many hours of listening and done many measurements and the quality of sound is in no way impacted by performing this way of voltage regulation compared to the powerstage running at the full voltage. The result is a nice acceptable sized housing with heatsinks that will not get hotter than 40'C.
And now the pictures plus a blockdiagram describing how everything is connected:
But these class-a amps generate a lot of heat resulting in big heatsinks and housings.
Because the ExtremA is a balanced amplifier design that has also separate powersupplies for the driver and powerstages, I had the possibility to add a way to regulate the voltage of the powerstage according to the level of music that must be played. Bias currents and gain are not affected by doing this. This is done completely in the digital domain.
SPDIF is taken in and converted to I2S and then fed to a big PIC32MZ controller that now checks for the peak level of the waveform and adjusts the buck converts by PWM to create the exact voltage needed for the level of sound. The audio is delayed just a little bit to make sure that the voltage is on the powerstage and stable just before the audio arrives at them.
From the PIC32 the audio goes to a DF1706 and four PCM1704 to convert the digital audio to analog and then feeding it to the two ExtremA amplifiers.
I have done many hours of listening and done many measurements and the quality of sound is in no way impacted by performing this way of voltage regulation compared to the powerstage running at the full voltage. The result is a nice acceptable sized housing with heatsinks that will not get hotter than 40'C.
And now the pictures plus a blockdiagram describing how everything is connected:
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Of you mean the displays, the bottom device which is a media payer build by me in the same style has a Noritake GU3900 vfd as display. The amplifier has a 7inch 800x480 lcd. Both displays sit behind two sheets of 3mm anthracite tinted plexiglass. The areas around the displays have been masked and spray painted black.
My idea from technics is that they adjust the bias actively based on the sound level. This amp was indeed somewhat inspired by Devialet and adjusts the voltage of the final transistors. I do not touch the bias.
the marantz ma700 do the same thing, increase the supply voltage to the output transistors