Noise & Bandwidth

We see a lot of the competition using basic computer parts to do the heavy work, and then using power supply designs and noise filtering to reduce the noise.  Many use add-on boards to re-do a job that was done poorly on their motherboards.  The trouble with this approach is that over-use of slow linear power supply designs and noise filters constrains bandwidth, and a digital audio signal needs a lot of bandwidth to square out the wave and thereby define the timing data with precision.

One way of putting it is that Antipodes uses fewer parts, but higher quality parts.  We also avoid taking quality short-cuts, with the parts we use, when trying to hit a price point.  For example, our least expensive music server is the Antipodes S30, but if you feed it with an Antipodes S60 power supply (an upgrade option for the S30), you get the same hardware and parts quality that we use for the Player stage in the K50.

But it goes further than just higher parts quality. One of the things we believe we do uniquely is to tune residual noise that cannot be totally eliminated. Imagine that three different chipsets generate noise that each peak at a frequency that reflects their clock speed. If the peaks coincide then nodes are created and the noise floor goes up dramatically at that frequency. Shifting the clock speeds can avoid noise nodes and reduce the combined noise level, as illustrated in the image below. Managing this for an entire music server is very complex, but yields significant benefits for sound quality.

If you compare an Antipodes music server with many of those from our competitors, you will hear a clear difference.  If you only listen for tonal qualities, you may not hear a fundamental difference.  But if you let yourself engage emotionally with the music you will hear more life, urgency and drama with an Antipodes music server.  Listening to music is about being moved emotionally – to make you want to smile, cry, dance …  Then you will understand why we take a different approach.

The diagrams below may make this clearer.

In order to get a perfect square wave digital audio signal, you need a perfect clock, zero noise interference on the signal, and infinite bandwidth.  With these three factors you can precisely define the transition point in time between one bit and the next.

Here is a graphical representation of a perfect digital audio signal.

This signal represents the data ‘01010’.  The ones are represented by a 1v level, the zeros are represented by the 0v level, and the clock data is defined by the vertical lines that define the transitions between them.  For argument’s sake, let’s say that the digital receiver recognises a transition from a zero to a one when the signal rises through the 0.5v level, and recognises a transition from a one to a zero when the signal falls through the 0.5v level.

Here is what happens when we add noise at a frequency that is below the bitrate.

Here is what happens when we add noise that is above the bitrate.

Here is what happens when the transmission bandwidth only just matches the bitrate.

Here is what happens when the bandwidth is one harmonic above the bitrate.

Here is what happens when we combine the impacts of some noise and some bandwidth limitation.

These examples over-simplify and exaggerate the point, but they do serve to illustrate how a combination of noise and bandwidth limitation obscures the clock data. But the point cannot be trivialised either as the perfect digital audio square wave is always going to be impossible to achieve. In the last graph above, it is obvious that the digital receiver is not going to be able to discern the transitions between the bits with perfect precision, because the timing of the transition through 0.5v is obscured.

This is what a high-end music server is all about, delivering the digital audio square wave with as much precision as possible, and no music server will ever achieve perfection given the real-world issues involved.