How Does the music get from a Digital File to the Speakers ?

In this series of posts we will see how a digital file is converted to music. We will see also see what parameters affect the quality of music we listen to.

First this would be the process.

MP3, FLAC or WAV file is parsed (decompressed if needed) by a computer (or a streamer ) and converted in to a PCM Stream (We will see how DSD works later). PCM stands for pulse coded modulation. In PCM a number that represents amplitude (loudness) of sound at a particular instant is sent few thousand times a second (for CD it is 44,100 times a second). This is called the sample rate.  So when we say 16 bit 44.1 Khz PCM stream , it means that the stream has 44,100 numbers for each second of music . The numbers range from 0 – 65,536 or (−32,768 to 32,767)  which is 2^16.

So a loud region will have numbers close to 40,000-60,000 and silent portions will have numbers less than 3000.

The digital signal is a square wave where Bit 1 is represented by 5v and Bit 0 any voltave <~2.5 , 8 such pulses(bits) from one byte of data.

These numbers are fed into a DAC (digital to analog converter), which converts these numbers in to voltage levels ranging from 0-2v (assuming 2v Peak to Peak output) . This analog signal is fed into an amplifier which in turn drives the speakers.

For more details you can read

So this system depends on getting those numbers into the DAC in a timely fashion without corruption.

We can assume that Digital Hi Resolution file we get has the correct data since it is not under our control anyway, our objective in our system  is to get this data as perfectly as possible to the DAC.

In our system let assume that we have a Streamer (PC or Dedicated Transport Device) which will give the raw decompressed digital data. The data might be sent over USB , SPDIF over Optical or COAX , I2s , HDMI etc based on the device.

you would connect a USB DAC or USB to spdif converter to the Transport to get the data out. Here the type USB receiver is very important.

For more details you can read


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