|23rd August 2005, 02:06 PM||#11|
Join Date: Aug 2005
The Wolfson micro parts are awesome.
I will get one and experiment with it.
I am not a seasoned DSP programmer, and to implement this I would have to stick to the only one I have expecience with-- dsPIC from Microchip.
In worst case, I could indeed implement the PCM-to-PWM conversion in firmware. But I assumed a dedicated chip could do it better, faster, more accurately.
Think about it: if you have a 16 bit signal to convert to PWM-- that's 64,000 individual timing quanta. Superimpose that on a PWM base frequency of 50 KHz, and you'd need a 3200 MHz clock to resolve 16 bits in PWM.
I can't implement that in a DSP, unless I reduce something.
Reduce bandwidth: (for subwoofer) 100Hz passband, with 1KHz PWM carrier.
Reduce resolution, 12 bit instead of 16.
That's 4096 x 1000, or about 4MHz PWM timing clock. Although doable, this stretches the limit of a DSP, since you will need to execute more than 1 instruction per PWM step.
But then you have a PWM carrier in the audible range. A subwoofer channel will imply hefty class D amplification post-processing.
A class D amp operating at 1KHz! -- great; the MOSFETS will like it.
Unless the whole circuit is dunked in epoxy and cemented, there may be some audible whine coming out of that.
I'll try both approaches
|24th August 2005, 09:59 AM||#12|
Join Date: Nov 2003
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