[sdiy] Audio hardware platforms?

[rsdio at sounds.wa.com]

Apple is not making a device that is primarily geared towards audio.  
They're making a general purpose device that does GPS, compass, cell  
(voice and networking), wireless networking, touch, massive GUI for  
endless possibilities in applications, and then also audio and voice  
recorder type features - all on top of a fairly sophisticated mobile  
operating system. It makes way more sense to use a general purpose  
processor like the ARM for that long list of features, rather than  
just specializing on one or two specific features.

But a couple of DSP opcodes in an ARM variant does not make those  
chips perform like a dedicated DSP, which has much more silicon  
dedicated to high performance of a particular kind. If you want to  
focus on audio, then a DSP makes the most sense. There are even some  
DSP chips, like the TMS320 C55xx family, that have USB and other  
hardware support that allow them to handle a display and basic  
interface tasks while primarily devoting the bulk of the power to  
signal processing.


Apple does have to worry about performance because they're a battery- 
powered mobile platform. But the fact that they're doing many things  
means that they need a processor that does reasonably well at a wide  
variety of things.

For an audio hardware platform, battery power might not be as  
important, since adaptors can usually be attached for power. But  
there's still some importance for performance, especially if you want  
to do a lot of effects without needing a high-wattage supply. The  
nice thing is that a good DSP can do more audio processing than a  
full-on computer (laptop or desktop) using far less power.


As for price, a well-designed DSP like the TMS320 is actually much  
cheaper than an FPGA chip when you really start doing complicated  
processing. DSP chips are very competitive with ARM on price, so I  
don't think anyone would choose ARM just to save money. The AVR can  
go lower in price, but the AVR cannot handle as much as the ARM or a  
DSP, so that particular choice is a price/performance tradeoff.

Brian Willoughby
Sound Consulting

p.s. I just discovered the XMOS chip, and that company has a few  
interesting platforms for development. I just saw the XK-USB-AUDIO- 
U8-2C, which actually has on-board MIDI I/O connectors along with  
stereo audio I/O and, of course, USB. There may be a plug-in board  
for an LCD, but I've not really studied their offerings. They do have  
a multi-channel audio I/O version, but that one does not have MIDI.  
They also have mini-board that plug in to the various main boards,  
adding optional peripheral I/O. As for something that can be sourced  
later for manufacturing, I think the XMOS development platforms show  
how there are just too many variations for anyone to make exactly  
what you want - it's a shame that their MIDI board is only stereo,  
while their multichannel audio board has no MIDI. I still think it's  
necessary to prototype on a generic board with added options, but  
then pay to have a purpose-built PCB made that fits your product  
enclosure and has exactly the I/O you need, no more and no less.


On Oct 12, 2013, at 14:15, Joel B wrote:
> Question, these DSP processors - are they a better choice than the  
> Arm Cortex/neon for music? Wondering since companies like apple are  
> using the Cortex series. Is it a price/performance thing?
>
> Joel
>
> Sent from my iPhone
>
>> On Oct 12, 2013, at 9:01 AM, Martin Klang <mars at pingdynasty.com>  
>> wrote:
>> stm32f4