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  1. #1
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    High freq noise from analog out?

    I have a 8-10kHz whine coming from SB right channel analog output, confirmed by swapping and experimenting with other components. I have entered a bug fix for it, maybe it is just something broken and not a bug. But for curiosity..

    Does anyone have similar high pitched whining noise coming from one or both channels of their SB 2/3? It is most easy to hear with SB connected directly to a high powered separate amplifier while SB is muted. The noise level does not change with software volume control, but music level does.

    I noticed it while trying the NuForce amps. I never noticed it before with the integrated amp where I use the amp volume control and keep SB S/N maxed with its volume control set to 40.
    Thanks,
    Rich

  2. #2
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    Yes, I have the same problem.

    I got mine replaced but the new one has the exact same behavior. I've been meaning to post a follow-up about this on my previous thread.

    Try this - change the screen brightness and notice how the pitch of the noise changes. Max brightness is bad, the next level down is worse, then the third level is about equal to the first. The two dimmest settings (dim and off) seem to be completely quiet. This happens for me whether the SB3 is playing, paused, or is in its "off" state. And only through the right analog out.

    Also take a listen to the headphone output. You should hear similar noise, but this time in both channels.

  3. #3
    Founder, Slim Devices seanadams's Avatar
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    How are your levels set? If your amp is maxed out and sb3 is set to low volume then you will be amplifying its noise floor substantially.

  4. #4
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    Quote Originally Posted by seanadams
    How are your levels set? If your amp is maxed out and sb3 is set to low volume then you will be amplifying its noise floor substantially.
    In my case I've run through two different setups:

    Setup 1: Wireless SB3 analog out to Paradigm Active/20s (self-amped speakers). The noise level does not seem to chage when I raise or lower the volume on the SB3 (muted through 40). Right-channel noise/interference level appears to be the same whether the SB3 is playing (though it's difficult to tell), paused, or "off". The only thing that affects the right-channel noise/interference is the display brightness.

    Setup 2: SB3 analog out to my Proceed AMP5, AMP5 to my B&W 703s. Same results.

    In both cases the SB3 is used as my volume attenuator so I can't run it at max level while playing music. However, the fact that the right-channel noise/interference level does not seem to change when I raise or lower the volume while it's not playing strikes me as odd.

    I've tested and eliminated the following possible culprits:
    - Audio cables (swapped cables, same result)
    - Local interference (moved SB3, same result)
    - Speaker issue (swapped channels, switched in B&Ws, same result)
    - Wireless connection (switched to wired Ethernet, same result)
    - Power supply interfering w/amps (moved plug to a separate circuit on opposite side of the room, same result)
    - AC line noise (plugged directly into my PS Audio UPC-200 line conditioner, same result)

    Digital out seems to be fine (though I'm wary about the digital coax after I ran into problems on my DAC. Toslink has worked well).

    Is it possible that the display is throwing off some interference that is being picked up by the right analog out (and the headphone output) after the attenuation stage?

    Can you locate my returned SB3 and give it a try? Or maybe grab a new wireless SB3 off the shelf and see if it exhibits the same noise?

    I'm sure you would have noticed this before if this issue existed from the beginning. Perhaps it's just a funny production batch? Or maybe a slight change in a vendor's part that's different from the original pre-production run?

    It's worth noting that my first SB3 only arrived last month and this replacement obviously is just about as new.

    For the original poster - how old is your SB3?

  5. #5
    Founder, Slim Devices seanadams's Avatar
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    Quote Originally Posted by banzai
    In both cases the SB3 is used as my volume attenuator so I can't run it at max level while playing music.
    This is bad. For a hifi setup you should use an attentuator or preamp, for safety reasons if nothing else. The problem is you are taking a DAC with a decent SNR, and then only using a *TINY* fraction of its range down close to the noise floor. I can not stress enough how detrimental this will be to the sound quality!
    However, the fact that the right-channel noise/interference level does not seem to change when I raise or lower the volume while it's not playing strikes me as odd.
    Actually, that is the expected behavior. The noise floor does not change when you use digital attenuation.
    Can you locate my returned SB3 and give it a try?
    I just did.

    http://www.seanadams.com/1.gif
    http://www.seanadams.com/2.gif

    1.gif is a full-scale sine wave, and 2.gif is the noise floor when nothing is playing (both plots are right-channel only). The peak you're hearing is at 8865 Hz and is at -120.70 dBr. The left channel is quieter, but still, 120dB down is very low **provided you have a reasonable signal level**.

  6. #6
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    I did one more test with a third setup:

    Wireless SB3 to old Yamaha RX-495 (two channel analog receiver) to B&W 602s3 at full volume (using Yamaha for volume control).

    At SB3 full volume, Yamaha at modest listening volume, the right channel buzz is basically not noticeable when SB3 is paused. However if I raise the Yamaha volume, the SB3 right-channel buzz does become apparent again. Admittedly, this level would be a bit loud for regular listening (guesstimating 80dB) but not completely excessive.

    Turning the SB3 down to the levels I have to use it at when it does its own volume attenuation (15 on SB3 volume control), and then turning up the Yamaha level to compensate makes the right-channel buzz much more apparent.

    I have re-confirmed that the SB3 volume level does NOT affect the right-channel buzz. In other words, the buzz is at a constant output level regardless of SB3 output level. The difference in hearing the buzz or not is based, as Sean suggested, on the output level of the amp.

    So really it's only an issue when the SB3 is used as a volume attenuator. At line-level (max) output the snr is high enough that the right-channel noise becomes insignificant.

    However, that still screws up my analog setup which relies on the SB3 to do volume attenuation and play at low levels.

  7. #7
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    Quote Originally Posted by seanadams
    This is bad. For a hifi setup you should use an attentuator or preamp, for safety reasons if nothing else. The problem is you are taking a DAC with a decent SNR, and then only using a *TINY* fraction of its range down close to the noise floor. I can not stress enough how detrimental this will be to the sound quality!
    Fair enough. After my last round of tests I can definitely appreciate what you're saying.

    The Paradigm Active/20 speakers can attenuate the input signal as it enters their self-powered amps. It's already cutting the signal, but I can drive it down a bit more while I drive the SB3 up. I'll have to see if I can cut enough off the input at the Active/20s to achieve a low enough listenable volume level while still leaving room for +/- volume control on the SB3.

    As for my temporary SB3 to AMP5 setup, I'm just out of luck since the AMP5 has no input attenuation (this was just a temporary measure anyway until my DAC is repaired). And it is an admittedly silly setup to begin with.

    Quote Originally Posted by seanadams
    http://www.seanadams.com/1.gif
    http://www.seanadams.com/2.gif

    1.gif is a full-scale sine wave, and 2.gif is the noise floor when nothing is playing (both plots are right-channel only). The peak you're hearing is at 8865 Hz and is at -120.70 dBr. The left channel is quieter, but still, 120dB down is very low **provided you have a reasonable signal level**.
    Okay, so moral of the story is: there is some trace right-channel noise but under recommended usage it shouldn't be an issue.

    The headphone output though still seems problemmatic. Unless you have an outboard headphone level attenuator you're stuck with a noisy signal.

  8. #8
    Senior Member JJZolx's Avatar
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    Quote Originally Posted by banzai
    The only thing that affects the right-channel noise/interference is the display brightness.
    How significant is the effect on this noise when you turn up/down the display brightness? I've seen concerns voiced elsewhere that the large display might be detrimental to the audio quality, but I this is the first time I've seen anyone say they can hear it.

  9. #9
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    Quote Originally Posted by JJZolx
    How significant is the effect on this noise when you turn up/down the display brightness? I've seen concerns voiced elsewhere that the large display might be detrimental to the audio quality, but I this is the first time I've seen anyone say they can hear it.
    Keeping in mind everything above (i.e. in terms of cranking up the amp w/the SB3 at low output levels), here's what I've noticed for each Brightness level:

    4 (Max brightness): audible buzz, but becomes masked during playback, even with volume super-low (e.g. volume = 1-5). It's still there, just difficult to hear unless you have a pretty quiet track.

    3: Buzz gains in pitch, becomes more noticeable, though perhaps overall volume is the same.

    2: Buzz returns to Brightness 4 level.

    1: Buzz seems inaudible. Left and right channels seem to only carry the basic DAC noise floor.

    0: Same as Brightness 1.

    I've configured my SB3 to set the base Brightness to 4, but the screensaver to Brightness 1 w/a 10-second activation. This way I can "wake up" the screen when I need to use the UI, but after 10 seconds it goes into screensaver mode and dims the screen again.

  10. #10
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    And I should add that at max volume with the amp/receiver attenuating, the SB3 DACs do sound very, very good.

    Overall I'm still very very happy with my SB3. The display-induced buzz at low levels is only a minor drawback (as long as you're not forced to rely on the SB3 as a low-level output device).

    As far as I'm concerned the SB3 is a stellar product that falls just a hair shy of perfect.

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