sbn;131587 Wrote: > Hi, I'm just wondering about how the "Preamp Volume Control" attenuation > works. > > I can see that it only impacts the analog outputs, so my first guess > was that it was using some kind of analog volume control, controlled by > the slimserver... > > But then i read about all these guys noticing a diffent sound via > SPDIF, using the -63dB tweak... And that means that the attenuation is > being done on the digital side of the DAC, right? > > If so, what is the impact on sound quality? I could fear that the > dynamic range was decreasing, due to a less amount of usable bits, but > maybe that's all wrong? > > In short: What's the impacts of the volume control and the preamp > attenuation, and how do they work?
The Squeezebox uses the Burr-Brown/TI PCM1748 DAC chip, according to Stereophile. The datasheet of the chip can be found here: http://www-s.ti.com/sc/ds/pcm1748.pdf. If you look at the first page of this datasheet, you'll see that the chip internally implements a variable attenuation scheme, 0 to 63 dB in 0.5 dB steps. It doesn't give details of the implementation though. To set this attenuation, the appropriate digital word is written to the serial control port. It's not at all obvious if or how this would affect the S/PDIF output, which is presumably tapped off upstream. I'll refrain from further editorial comment :-). -- andy_c ------------------------------------------------------------------------ andy_c's Profile: http://forums.slimdevices.com/member.php?userid=3128 View this thread: http://forums.slimdevices.com/showthread.php?t=26788 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
