Guidance on DSP and DAC IC’s To Use
Hi,
I am building some 3-way Active Speakers, and I have designed the analogue filter stage, and in implementing the PCB design, the size of the PCB is large.
After searching on DSP audio boards there are a number of open source products which are quite cheap using the ADAU1701 DSP. Further examination of the results has shown that there is a magazine ADAU1701 board (sold out) but this uses the Analog Device SigmaStudio software which is free.
Therefore, it will be optimal to use a DSP solution.
The requirement is that the DSP board will have 2 analogue inputs, 1 digital input (SPDIF), and 6 or 8 DAC outputs. My proposal is to use 3 stereo or 6 mono DAC IC’s. The questions I have to select the DSP and DAC IC’s are as follows :
Preference is a floating point DSP, with the smallest number of pin outs, using the low profile Quad Flat Pack implementation so as to allow hand soldering onto the board.
The DSP chip is to have 6 or 8 SPDIF outputs.
The DAC IC’s required to be 32bit, hence can the DSP output 32bits on the SPDIF outputs ?
The DSP is required to have similar to ADAU1701 microcontroller-like control interfaces.
Would fixed point DSP be acceptable for (6 or 8) x {4th/8th} order linear phase filter implementations and volume control for each of the 6, or 8 SPDIF outputs ?
Possible implementation of an infra-red receiver – could a DSP implement this aspect with little impact to processing of the other signals.
Are there any guide designs for implementation of the DSP IC to ensure that it can integrate with SigmaStudio ?
The list of DSP’s available that are compatible with Sigma Studio is quite large, so for a person not well versed in DSP, to determine the optimal DSP is difficult. Therefore, I am grateful for any guidance as to which DSP to use to met the criteria above.
Thanks and regards,
Richard.
Audio Signal Processors
dsp
sigma studio
SigmaDSP Audio Processors
adau1701
Hi,
To answer some of my own questions after reading some of the initial pages of the datasheets. There are a limited number of products that are suitable - since the preference is for outboard DAC's.
The ADAU1466 offers the maximum capability for the requirements - and this is stated to be a fixed point processor.
The SPDIF outputs outputs - this was an error on my behalf - i should have stated 8 audio outputs. This is possible since there are 4 serial outputs on the ADAU1466, where each can provide a stereo bit stream (or more), hence there are at least 8 output streams.
It seems that the serial outputs are maximum 24bit words.
The ADAU1466 seems to have similar interfaces as per the ADAU1701.
I installed SigmaStudio onto a VM - and can see from the help files and examples it offers a 3-way crossover. There is also a volume control example.
From SigmaStudio, does not indicate if it can implement the code for an Infrared receiver. I am not sure it has the capability to implement as such.
I examined the EVAL-ADAU1466 board - and as per the EVAL-ADAU1701 board, the serial EEPROM can be programmed using the EVAL-ADUSB2EBZ board, if you follow the design of the boards.
I will need to add a 51us and 127us delays (buffer) to the Woofer and Mid-Range signals - not sure if the ADAU1466 has the memory for this ?
For the volume control - can a separate micro-controller signal on GPIO pins up and down volume control ?.
Regards,
Richard.
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