Hi Dave Dave Malham <dave.mal...@york.ac.uk> a écrit : > Hi Marc > > I've certainly thought about doing that, but not initially since it > means that > > (a) you would be limited to passive speakers
This limitation is a feature: with less hardware the cost is lowered and the quality is raised. It would be a good choice to create small domestic systems or public installations. It would be adequate with 6 or more identical full range speakers. > (b) the specs aren't as good as the Analog Devices ADAU1966, the > evaluation board for which is sitting next to me :-) The better spec of the ADAU1966 is rarely matched by amps and speakers... I agree that for professional use it would be perfect. ;-) > (c) serious levels of hardware design needed for the power amps stages In the example application schematic the D-class amps with PWM inputs are connected directly to the PWM ouputs of the TAS5508C. How easier can it be? The final system could be made in the form of a PCM to PWM decoding board to connect amps with PWM inputs. > on the other hand, the TAS5508C has a "Full 8×8 Input Crossbar Mixer. > Each Signal-Processing Channel Input Can Be Any Ratio of the Eight > Input Channels." and "Mixer gain operations are implemented by > multiplying a 48-bit, signed data value by a 28-bit, signed gain > coefficient" so.... 8 speaker digital decoder, anyone? Only problem > is, no way to implement shelf filtering :-( Interesting! But its only job would be to interface PCM streams to PWM inputs. There's also stereo D-class amp chips with I2S inputs. Marc > > Dave > > On 10/07/2012 02:20, Marc Lavallée wrote: > > Dave, > > > > It's possible to skip the A/D conversion by using amplifiers with > > digital inputs. Texas Instruments have a 8 channels digital to PWM > > converter that can drive D-class amps with PWM inputs; that means > > only one A/D conversion, done by the speaker... > > > > http://www.ti.com/product/TAS5508C > > > > Marc > > > > > > Wed, 25 Apr 2012 15:51:02 +0100, > > Dave Malham <dave.mal...@york.ac.uk> a écrit : > > > >> Hi Marc, > >> True, I'm sure you could use a usb interface, but even a low > >> cost multichannel unit would be quite a lot more expensive (and, > >> probably, power hungry) than the PI whereas Analog Devices (for > >> instance) do a 16 channel, 24 bit, 192kHz DASC IC for around 10 ukp > >> (ADAU1966) which would probably need around another 20 quid's > >> worth of op-amps and other bits to get going properly. Much more > >> in the maker tradition - and a possible product. > >> > >> Dave > >> > >> PS total number of pre-orders for PI's have reach 350,000! > >> PPS I'm not connected with them at all, I've not even ordered one! > >> > >> On 24/04/2012 18:33, Marc Lavallée wrote: > >>> The snd_bcm2835 driver is for the integrated stereo sound module. > >>> For more channels, a cheap 8 channels USB sound module would > >>> probably work, and ALSA drivers for many sound modules are stable. > >>> > >>> Martin Leese<martin.le...@stanfordalumni.org> a écrit : > >>> > >>>> Dave Malham<dave.mal...@york.ac.uk> wrote: > >>>> > >>>>> The Raspberry PI is really cheap and runs Linux, so it does > >>>>> provide some real possibilities, though > >>>>> it is, in some ways, quite limited - max 256m ram at present, > >>>>> for instance - > >>>> ... > >>>>> it seems that the SPI pins are available on a standard header so > >>>>> shouldn't be too difficult > >>>>> physically to add DAC's or ADC's (since most use that > >>>>> interface), though how easy it would be to > >>>>> write the drivers, I don't know. > >>>> The Arch Linux ARM image (operating system) > >>>> contains an ALSA driver. However, it states: > >>>> > >>>> "The alpha-quality ALSA driver included in this > >>>> release is disabled by default. Type > >>>> modprobe snd_bcm2835 > >>>> to enable it." > >>>> > >>>> Regards, > >>>> Martin > > > > _______________________________________________ > > Sursound mailing list > > Sursound@music.vt.edu > > https://mail.music.vt.edu/mailman/listinfo/sursound > _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
