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Faint hum....

I've been struggling to understand this issue for a while...my integrated amp has 2 RCA inputs, 1 XLR input, and a few digital inputs (Toslink, Coax, etc). When I turn the system on, i'm usually on either RCA1 (CD player) or RCA2 (phono stage connected), there is a low hum in the speakers. If I increase the volume, it gets louder. If I mute the amp, the hum goes away. It's noticeable, but it doesn't bother me when the music plays. What I find it somewhat strange is that it has the same volume if i switch between RCA1 RCA2, and XLR (I have nothing connected to this input!!!). But when I switch from one digital input to another (Coax, Toslink1, Toslink 2), there is no hum. Everything is dead quiet.
So what's going on? Is there anything I can do to eliminate this hum? I tried all sorts of interconnects, speaker cables, the hum remains when I switch from one analog input to another. It might have different intensities, but no cable got rid of it.
iasi
schmitty1
46 posts
 
Bad filter cap in the power supply could be at fault. IMO
Post removed 
iasi OP
115 posts
 
i unplugged everything from the int amp...turned it on and the faint hum is present whenever one of the three analog inputs is selected...the hum disappears when one of the 4 digital inputs is selected...i changed the power cable for the int amp to the one with 2 prongs...no difference...anyway, it is not that obtrusive when the music is playing. i was just trying to understand why is the hum present only on the analog inputs and not on the digital ones.
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twoleftears's avatar
twoleftears
5,318 posts
 
Yes, if it's only a question of which input is selected, even if no component is attached to that input, then it obviously sounds as if the problem is internal to the amp, especially as digital input is quiet.  Hum on any/all of the line-level analog signal inputs, then?  What make of amp?
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