High Definition Digital Audio Signal Chains in the Car – From Source to Amplifier

Digital Audio in a car is a wonderful thing when rendered properly. Just like analogue audio, digital audio signals can be affected by system losses. The loss takes a slightly different form as it is bits that are dropped which can have a subtle but very real affect on the resulting sound. In the early days of digital, it was quite common to hear people complaining that the sound was hard, and spiky and generally not very nice. Much of this was not necessarily down to digital rendering per se but more due to data loss and poor digital to analogue conversion strategies. The data rate of CD for instance was decided for purely arbitrary reasons (It was all Beethoven’s fault!) and this held digital audio back for many years.

With the dawn of hi res audio as well as huge steps forward in digital to analogue conversion algorithms and associated hardware, things have become much better. Some will always claim that their static crackle-prone, largely mono recordings replayed from spinning vinyl sounds better than anything else and it is best not to argue with them in my experience. In a car, there is nothing quite like a totally pure digital rendering of a piece of music devoid of distortion and other physically generated artefacts. Even 16 bit CD, when properly reproduced and with utmost care given to data preservation and accuracy of information, can be a beautiful thing.

Italian high-end car audio innovator Audison has been leading the field for a while in providing car drivers with the purest digital signal chains possible.

Their latest “High Definition” offerings are capable of reproducing digital recordings and carrying them in the digital domain to processors and even amplifiers whilst still in the digital domain. This results in only one conversion from digital to analogue being required, which happens in the amplifier. The simplest way for Audison to do this was to create their own hi-res source unit known as bit Play HD. This clever box is capable of reading hi-res files (FLAC files for instance) with a word length of 24 bit and a sampling frequency up to 96kHz. The result is output via a TOSLINK connection to the optical input of a processor (bit One HD) where signals can be split into many channels and filtered and shaped while still in the digital domain. The result can then be digitally transferred directly to an amplifier (Audison Voce AV 5.1K HD for instance) where the signal is converted to analogue and sent on its merry way to some speakers without any loss or anomalies often associated with too many conversions!

There are still many who do not yet get hi res audio, mainly due to not having experienced it over a period of time. The differences are very real but initially quite subtle. Without the equipment to properly squeeze the most out of it, the difference can be missed. This is unlike HD TV, which is quite obvious to many more people due to the eye being most people’s dominant sense. Having listened to quit a lot of hi-res music over the last three years, we are convinced that this coupled with the purest signal chain possible is the way forward.

Car Manufacturers are adopting a technology called “MOST” (Media Oriented Systems Transport) as a way of passing digital signals around a car. In many cases, audio data is carried on this buss and Audison has a product called bit DMI capable of collecting this and carrying it forward for processing and amplification. This makes a huge difference to CD listening in the car as any tricky signal fiddling added to protect appallingly low quality speakers from bass and other distortions can be effectively bypassed. The result is unerringly accurate information leading to better dynamic response, clarity and linearity.

Of course, the best place to go to find out more is your local FOUR MASTER who will be able to point you in the direction of mobile audio nirvana!


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