seanadams Wrote: > FWIW SB2/3 already exceeds the manufacturers' specs for both the E and > the KE parts by a good margin - dig back in the archives for some other > comments on K vs KE. One off the mods I have tested is the super > regulator and this indeed pushes it a bit further in terms of lowering > the noise floor. Some test results here: > http://www.seanadams.com/sb2_super_regs/ > > I haven't tried Vinnie's changes yet so I can't really comment except > that you will have a 1Vrms output voltage and no LP filter, so the > sound will surely be different. Thanks Sean. 1V is about a volt and a half shy what of what it takes to drive my power amp. I also assume that bypassing the audio output opamp raises the source impedance to some degree, which may have an added impact in its ability to drive a power amplifier. As you mentioned, the loss of the two pole filter by Vinney's mods goes against the manufacturers' application notes:
-"Delta-sigma DACs use noise-shaping techniques to improve in-band signal-to-noise ratio (SNR) performance at the expense of generating increased out-of-band noise above the Nyquist frequency, or fS/2. The out-of-band noise must be low-pass filtered in order to provide optimal converter performance. This is accomplished by a combination of on-chip and external low-pass filtering. Figure 27(a) and Figure 29 show the recommended external low-pass active filter circuits for single- and dual-supply applications. These circuits are second-order Butterworth filters using a multiple feedback (MFB) circuit arrangement that reduces sensitivity to passive component variations over frequency and temperature. For more information regarding MFB active filter design, see FilterPro MFB and Sallen-Key Low-Pass Filter Design Program (SBFA001), available from the TI Web site at http://www.ti.com."- http://focus.ti.com/lit/ds/symlink/pcm1748.pdf -- mac ------------------------------------------------------------------------ mac's Profile: http://forums.slimdevices.com/member.php?userid=932 View this thread: http://forums.slimdevices.com/showthread.php?t=18491 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
