I just finished recommissioning my old Rotel system as the world's largest distributed alarm clock in the bedroom.
My alarm clock configuration is SB3 -> Rotel RB-890 -> B&W Matrix 805 bookshelf speakers. Note that the SB3 is about 6.5 dB hot on line levels for the RB890 (1V input sensivity). I *do not* have proper analog attenuators installed yet (still looking for an easily orderable Canadian source), so the noise floor is definately double the volume it should be. I have the Preamp Volume Control set to -6.5 dB to keep me from being blown out of bed in the morning by accident. Since the RB890 has no trigger I leave the amp on even when the SB3 is in powered off mode (not really off...). The SB3 is set not to turn off audio when "powered off". I have noticed that on the right channel only, with no music playing, there is a perceptible high frequency tone. It is very low volume, right in the noise floor. Because the room is so small and quiet, I do hear it even a few feet away. I have tried the following steps to debug this: 1. I swapped the R/L channels at the SB3. The tone follows the channel (i.e. when I swapped L for R the tone moved to the L speaker). 2. I flipped the SB3->RB890 RCA cable R/L on both sides. Problem remained on the R channel. 3. I tried a second SB3 I have on hand, same results. 4. I moved the wall wart switcher PSU from right beside the amp to around a corner, far away from the amp. 5. I have changed the brightness levels. (1) implies the problem is either the SB3->RB890 interconnect cable or the SB3 itself (problem moved channels, so it is not the amp or interference on the speaker cables) (2) eliminates one side of the cable as the problem (if it was the cable problem should have moved to L channel). (4) requires more explaination because it is the only change that impacts the tone I have made so far. The SB3 has 5 brightness levels (0 - off, 1-4 from dimmest to brightest). On display brightness 0, 4, and 1 there is no tone that I can pick out. Brightness 3 has the loudest tone. 2 is much less noticable. The pitch of the tone is related to how much text is displayed on the SB3 screen (the tone changes between lots of text and a little text are not large). If I had to guess i would say the R channel in the SB3 is picking up some RFI from the computing cycles. This rates as a "nit" not a big problem, because I do not hear this tone when playing music (usually at volume 40-50 right now). Its just an issue when not playing music because I leave the amp powered up and the tone is somewhat evident. Has anyone else experienced this? Will this go away with proper attenuation? Are there any other suggestions to resolve this? -- Eric Carroll ------------------------------------------------------------------------ Eric Carroll's Profile: http://forums.slimdevices.com/member.php?userid=9293 View this thread: http://forums.slimdevices.com/showthread.php?t=32045 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
