To be able to use a DSP a digital signal has to be available (like e.g. coming
from a CD). Is the signal analogue an analogue-digital converter (ADC) has
to be used to convert the signal into a digital signal. The digital signal
available usually in 8, 16 or 24 bit (digital on/off switches) and running
through 1, 16, or 24 bit signal lines may then be processed.. Afterwards the
digital signal has to be converted into an analogue signal so that loudspeakers
are able to reproduce it. That's done by a digital-analogue converter (DAC).
The 3 steps:
- DSP processing
- conversion back to analogue
to be seen on the left.
Picture 1: diagram for acoustic signal processing with analogue
The Sitronik or Audaphon DSP-modules feature 2 ADC's, one for each stereo channel.
The digital processor receives, therefore, two signals (left/right) from the
ADC, already digitised with 24 bit and scanned up to 96 000 times a second.
The processor now calculates three signal:
- a new output signal for the left channel
- a new output signal for the right channel
- a output signal for the subwoofer
The processor possesses extensive facilities to adjust the signal on all three
Let's assume your glass cabinet has a resonance at 8.5 kHz, then The DSP is
capable of suppressing 8.5 kHz on all three channels. It's also capable of
adjusting the skew of your loudspeakers - when they are not positioned the
same distance from the listening position -, the phase and may boost frequencies
that your loudspeakers are reproducing too softly.
These three digital signals are then converted back to analogue using a DAC,
for left and right channel and the subwoofer.
The digital sound processor (DSP) is made by Motorola: DSP 56364FU100 (refer
Picture 3: diagram of the digital sound processor Motorola
The heart of the processor can be seen in picture 3 below right: the DATA
ALU (ALU = arithmetic logic unit).
The remaining components are auxiliaries, programme and data memory that
is extended by the way on the Sitronik PCB. There are data circuits (to the
ADC and DAC), control circuits and address circuits (for addressing the external
The analogue stereo signal arrives at AIN1L and AIN1R and is then converted.
The 24 bit signal is sent bit-by-bit as ASDATA 1 and ASDATA 2 (on the left,
just above the middle) to the DSP.
The signals coming back from the DSP are sent bit-by-bit to DSDATA 1 and
DSDATA2, respectively DSDATA 3 for up to 3 stereo channels (e.g. 5+1). From
here the signals are sent via volume and filters to the DAC's (on the right).
The analogue signals are then available at the outputs Aout1, Aout2, ... 6.
DSP: room tuning back to Sitronik