-Do you think (theoretically even) that the sound on the SB2 could be improved by changing the power supply?-
In my experience (having done it) there's no doubt at all. I do have some reservations over the RA Powerpak's though - they are SMPS, which is part of the 'problem' in my view, with the supplied PSU. I've had a bit of a prod around inside and outside my SB2 (wireless version) and discovered some intersting stuff (like Sean did a good job on the design ;) ). For starters the supplied SMPS supply is pretty noisy, compared to what is possible from a well-designed linear PSU: - [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/Noise%20Comparison.gif] BUT, as Sean has pointed out, this external supply has a long way to go before it reaches the circuits inside. Even though, the linear supply has a quite marked effect on some of the internals, for example: - [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/14V_internal_supply.gif] The above shows the effect of the noise out of the 14V internal supply (derived from the display) when fed from the SMPS and the linear supply (red trace is the noise floor of the measurement system). The 14V supply is a lot noisier, especialy at HF, when the SMPS is used. Interestingly it also changes with the brightness level of the display: - [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/14V_vs_display_brightness.gif] Both of these plots are worse again with the SMPS supply (not shown). Having said all that, the most critical supplies, the 5V and 9V linear internally regualted supplies are commendably quiet and show good engineering, design and layout around the audio sections: - [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/5V_internal_supply.gif] and [image: http://www.alw.audio.dsl.pipex.com/Downloads/SB2/9V_internal_supply.gif] These don't tell all in my view or experience though - whilst there's little evidence in most cases of the 14V supply (that feeds the 5V / 9V regs) breaking through to the audio circuits, the reg's will be affected by this noise, and in my view (and actual experience) the effect of a better external supply is clearly audible in my experience. Measurement in this relatively simplistic manner doesn't tell the whole story. Andy. -- Andrew L. Weekes _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
