seanadams Wrote: > Well this is fascinating - the short answer is yes we can probably make > it work. > > Our noise floor in the audio band is down at -127 dBu. However > delta-sigma DACs inherently generate impulses (high frequency content) > of some couple hundred microvolts even when fed a DC level - i.e. you > trade much higher performance in the audio band for some out-of-band > noise. Even for all-zeroes the DAC is actively working to hold the > output between two levels. > > So what is tripping your amp is probably this component of the noise > floor. Looking at the rms level of noise floor it is about -60dBu when > the DAC is active. I tried setting the attentuation to -64dB (mute) but > this apparently does not actually disable the DAC, it's the same as > playing zeroes. Next I tried inhibiting the clocks completely, which > worked - it goes down to -90dBu, which is the same as the analyzer > measures with RCA cables not connected to anything. Next I tried > disabling the DAC by setting its reset bit. This worked too. So with > some smarts in the SB2 to shut off the DAC when appropriate we should > be able to do this. > > http://www.seanadams.com/sb2_noise_floor.gif > http://www.seanadams.com/dac_disabled.gif
Sean, Any update on this as my powered sub-woofer which is directly connected to the sb2 along with my amp (thru a y rca splitter) stays on all the time due to the noise floor issue. -- rme _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
