Hiss on audio, but only when nothing is playing and the sound is active
  • pilesofspam
    First, PiPlay is awesome. I'm building a hidden coffee table emulator, and this is going to make the hardware part of it pretty much trivial.

    I do have one problem: I have Pi model B+, and there's a distinct audio hiss that sounds like white noise. Specifically, if you boot to command line (not the menu), then there's no hiss. When you start the menu, you can hear the familiar *click* of the audio device starting (not a problem) and then the hiss begins. Here's the interesting part: When you move the selector, getting the familiar muted *bong* the hiss disappears while the bong is playing, and then restarts. It's not that I just can't hear it, the hiss actually stops while the sound plays. The same thing is true in mame4all. Silence in 'joust' sounds like somebody left the water on, but a 'flap' temporarily silences it.

    Checking other RasPi forums, most people with this problem experience it all the time, and it's usually as a result of a noisy 5V power supply. I swapped mine temporarily with a fairly high quality bench supply and there's no change. Any ideas? It's not THAT loud, but I'm no audiophile and it's pretty obvious, so maybe I've got some 'special' hardware here. I have a RasPi model B (original) so maybe I'll give that a shot as well.

    Let's see- other details- I tried direct connecting with headphones alone as well as 2 different amps. If the noise sticks around, I'll probably pick one of these up and give it a shot:
    http://www.ebay.com/itm/PCM2704-USB-to-S-PDIF-Converter-DAC-Sound-Card-Board/191097084845

  • mholgatemmholgatem
    have you tried updating your alsa drivers? Also, try turning down the raspberry pi volume, and turning the speakers up. are you running through 3.5mm or hdmi?
  • pilesofspam
    Thank you for the reply! I didn't specifically update the alsa drivers, but I did run an update on everything, assuming that picked up the latest version. Version info below. I am running out of the 3.5mm headphones jack. I thought it might be due to picking up some noise from the composite video, but the noise doesn't change based on what's displayed. I actually had some luck crankingdown the pi volume and decreasing my amp volume, which decreases the amplitude of the noise at the speakers, changing it from really bad to merely annoying, so that's a good recommendation.


    apt-cache policy alsa-base

    alsa-base:
    Installed: 1.0.25+3~deb7u1
    Candidate: 1.0.25+3~deb7u1

  • pilesofspam
    I tried on the Model B original (the one that came with 256MB ram) and found the same effect, so it's not a specific hardware thing. I put it in an obvious mode (amp turned up a bit, sound volume turned to 50%) and took this recording while in launchmeny.py (you can hear the hiss go silent when I change the menu selection):

    Noisy audio link

    Does anybody else hear this? If not, and since I'm seeing it on both the Model B and B+, then it MUST be something else I'm using. Maybe I'll go back and check power again. This recording was taken using an Ipad charger for power.
  • tearexairz
    i have the same hisssssss its terrible. i find when connecting through the audio jack with a pair of head phones i get no hisss. but if i use any type of powered amp its there and its loud. i bought a small USB audio device, just waiting for it to arrive. hope that solves the problem. http://www.adafruit.com/products/1475
  • ian57ian57
    Hello,

    i've got the issue since the last update. I think it comes from the latest firmware. But i changed the power supply in the same time !

    I noticed that when games are stereo (1944 for example) everything seems to be good (no hissss), but when the game is mono, 1 speaker is good and the oher one makes hissss.

    When no sound is played, my left speaker gives hissss , but not the right one.

    I think it comes from mono/stereo management...

    anyone can confirm that?

    [edit] I will try to change my power supply of the pi, -> http://forum.stmlabs.com/showthread.php?tid=3092
  • pilesofspam
    Not seeing quite the same thing. My noise is from both speakers, but when I start, say, Joust, it plays the hiss until I start the first game and the first sound is heard. Then it's gone, but kind of sneaks in now and then when there's silence during a game. Stereo games are about the same. Both speakers are affected when I hear it. I have a PCM2704 board on order (about $7 on ebay), I'll post back here with results when it comes in.

    I tried power supply changes (including a DC battery with a linear 5V supply) to no avail. Usually it looks like this is the problem- let me know how yours works.
  • ian57ian57
    I changed the power supply this morning, ssame thing, the left speaker makes hissss

    i checked that my amplification device is working good with a mp3 player. No Hisss with it. SO it comes from the output of the pi.

    I'll check my alsa config
  • pilesofspam
    Boosting the master output on ALSA helped- it seems that the hiss is constant volume regardless of ALSA setting, so a volume boost increases S/N ratio. I'm somewhat limited in that regard though, since my amp is based on an ST class D part:
    http://www.st.com/st-web-ui/static/active/en/resource/technical/document/data_brief/DM00067996.pdf
    I don't have a linear volume control. Still, it's efficient, so no heat sinks or extra power.
  • pilesofspam
    My PCM2704 board came in yesterday. I can say that without a doubt, I'm happy- the hiss is gone, the sound is great.

    It wasn't plug N play though- you'll need to follow a guide like this one:
    enable USB audio on the pi

    Then after a reboot, fire up alsamixer and make sure your USB sound card (you might have to hit F6 to get the the usb sound card controls) is set to volume > 0. Works great. My test is TMNT, which really botches the audio even in the attract screen when something is off. Sounds perfect now.
  • ian57ian57
    I made some tests.. and it comes from my sound amplifier... I think it does not filter well the signals. I tested others amplified sound speakers and oit works well....

    I need to check the first one...
  • lateolateo
    This issue is firmware based from my experience (got to this point after a firmware update on a pi B).
  • Freddy
    I have the same problem, both on B+ and a P2. Anyone got a solution except getting a USB audio card?
  • BMDK
    Same problem here when using the the 3.5mm. Using the HDMI there is no hiss. On a pi2 here.
  • atv223
    I chased this issue for so long I gave up and just bought a USB audio card. For as cheap as they are I wasted WAY more time trying to chase this down. I am tempted to believe it's actually a problem with some of the boards themselves. Between it not being all of them and a lot of people just using HDMI audio, it just never gets tracked down to firmly diagnose.
  • oggie
    I have the same problem. low audio levels. And if I turn up the amp, I get hissing.

    I don't have any hdmi audio on my monitor, so I can't use HDMI for audio.
  • EkDor
    I get a background noise. Using Pi2b. HDMI to DVI-I with composite Audio. I have noticed that it starts during the boot process. Presumably when Audio is loaded. But interestingly if I "Accidentally" cause the PiPlay menu to not load (reverts to terminal) static doesn't start at all. I do hear a pop during the load at about the time the noise normally starts. On mine; the following config causes this to happen:

    config_hdmi_boost=4
    hdmi_group=2
    hdmi_mode=4
    disable_overscan=0
    overscan_left=24
    overscan_right=24
    overscan_top=24
    overscan_bottom=24

    This suggests to me that the fault is within the software.
  • mholgatemmholgatem
    @EkDor - it's mostly (but not completely) the 3.5 audio output that causes the noise. The reason that you don't hear it in terminal, is that it automatically turns off the audio until it is needed. The way that PiPlay works (more specifically, the pygame sound library) is that you initialize the audio then it waits to receive audio commands. While it's waiting, it's still active, so you can hear all of the line distortion. (It's an analogue signal, so they would need to add better audio filters to the pi in order to correct this.) If you use a digital signal (hdmi or usb-audio), you won't hear these audio artifacts.

    Now that being said, we technically could de-initialize the audio in piplay until it is needed for SFX, but that would cost us in cpu-performance and for the time being, we are very much concentrating on keeping the cpu workload at a minimum since there is such a disparity between the pi 1's and pi 2'2.
  • EkDor
    Thanks mholgatem; I just added this to my config and the hiss is gone:

    disable_audio_dither=1
  • mholgatemmholgatem
    nice EkDor! I didn't even know that was an option for the boot config
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