Hello
I bought AMP+, connected it with A+ and with ceiling loudspeaker. Everything works fine. However I miss one important functionality - turning AMP off by a software!
The thing is there is a hiss even when volume if at zero. It is hardly noticeable but it is irritating. What I need is a possibility to switch current off completely that drives speakers.
I noticed that hiss started when linux loads HIFIBerry driver which made me think - it is possible to switich amp off on a driver level.
HIFIBerry Team, please tell me you have this functionality in your software...
Thank you in advance
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8 comments
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HiFiBerry team Hi,
no, unfortunately you can't turn off the Amp by software. The used chip does not have a function like this.
Best regards
Daniel -
hsmeets Strange, no hiss or noise at all even not with volume set at max and this is on efficient speaker. So maybe the hiss not originates from the AMP? Maybe RF interference from transformers used in modern LED or Halogen lighting? -
Andrej Kislovskij Hello
It's unfortunate there is no feature like this. However after some testing I still think there is similar functionality.
The thing is there is no hiss when hifiberry amp driver is not loaded. This fact make me think that driver somehow "enables" or "unmutes" amp.
Could you comment about driver initialization routing? Is there "enable/disable" or "mute/unmute" functionality that can be used by user-space software?
I am also thinking about making some tests whether loading/unloading kernel modules make any effect on hiss. As far as I know it should be easy with kernels <= 3.17. Do you know how to load/unload your driver with kernel 3.18?
Thank you in advance. -
HiFiBerry team Hi Andrej,
there is no such function that can be used by user space software. You can try to unload the driver. However this might break the ALSA subsystem. The chip itself has no mute function.
Best regards
Daniel -
Andrej Kislovskij Hi
You are right, once amp is activated by hifiberry driver hiss is present even if driver is not loaded.
So my next step will be checking if hiss is caused by power supply (I use cheap 14V power supply from China). I was hopping that amp has a very good power regulator so power supply does not have any affect.
Could you comment whether power supply causes any "side effects"?
Thank you in advance -
Andrej Kislovskij Hi
Just tested with clean DC power (I used car battery that was giving 13V). Hiss was just slightly less :(
May be I was not clear about level of hiss I am talking about: I can hear it only when put my ear <10 cm away from the center of a loudspeaker.
As far as I understand there are two options:
-> This hiss is due to some RF interference
-> I am expecting too much from a 60 EUR board and it is normal behavior
Any thoughts are much appreciated -
HiFiBerry team Hi Andrej,
a bit of residual noise is normal for any analog component. It also depends on the efficiency of the speaker. As different people hear different things, I can't say if it is normal. However if you're not happy with the Amp and you bought it directly from us, you can return it to us. We have a money-back-guarantee.
https://www.hifiberry.com/shop/money-back-guarantee/
Best regards
Daniel -
Andrej Kislovskij Hello Daniel
I got confused when I saw comments saying there was no noise/hiss at all. In my case hiss is noticeable only from <~10 cm., .so in general the amp is good enough. "Turn-amp-off" functionality could resolve this minor issue, so you might consider it for future upgrades.
Anyway I am keeping it as it suits my use-case (I plan to use it to stream music in the bathroom).
Thank you for your support.
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