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"Amplifier Noise Floor" and hum acceptable?

I recently purchased the Parasound A52+ (5 channel amplifier, 180 wpc all ch driven). Initially I loved it and had no issues. About 2 weeks in however I was sitting around quietly and noticed the dreaded 60 hz hum. I get up close to the speaker midrange driver (Focal Aria 936) and there it is blaring at me. It is present in all 5 speakers I have connected. Everything is connected on a single dedicated receptacle with a power conditioner.

Trouble shooting.. the hum is not affected by volume control on the preamp. When I have removed the XLR cables to the preamp and ONLY have the speaker cables and the power cable connected... it hums. I did recently change my receptacle from a stock to a Hubbell but I don't think this would affect it. I upgraded my power conditioner too to see if that would do anything (I didn't think it would) and it did not. I switched the parasound out for a class D amp (120 wpc) and there was almost no hum. I switched it out for another class AB amp (140 wpc) and there was a hum but about half the volume of the parasound. 

So here's the gist.. when I emailed parasound tech support there are 2 things he said that I thought were noteworthy. One, he states that it is typical and normal to have some hum that close to the speaker baffle, i.e. within 1 foot of it. Second, while I asked for help he ultimately just said "I think you are just hearing the amplifier noise floor".

Three questions I pose to the community. 
Is it normal to hear a hum next to your speak baffle?
Is it acceptable and normal to be hearing the "amplifier noise floor"?
What can I try to lower this noise floor? I thought about connecting a ground wire between the chassis of the A52 and my power conditioner as the next step...

Thanks in advance for input.
jwl244
don_c55
1,025 posts
 
It is 2021, any audible amplifier noise floor and hum is unacceptable to me!

I put my ear on the twitter and hear no audible noise or hum.

Your Parasound amp has a ground loop problem IMO.
ditusa's avatar
ditusa
1,883 posts
 
@jwl244,                                                                                                                                OK. When you changed your receptacle to the new Hubbell did you cheek the Hubbell for phase. If you reverse the hot and the neutral on the receptacle by mistake, it could cause a hum. BTW: The faint hiss from the tweeter, is the amplifier gain just lower the gain knob on the back of the amp. Hope that help. Mike
jwl244 OP
64 posts
 
@ditusa thank you for that. I will have to check on what you said. The faint hiss I don't mind so much but thanks for that knowledge as well!
jwl244 OP
64 posts
 
For updates
1. The receptacle neutral and hot wires were not reversed. I checked.
2. I switched the new Hubbell recep out for my old one (common 20 amp one). Hum was still there. 
3. I bought a new and better power conditioner. Hum did not change.
4. I lifted the ground with a 3 to 2 prong adapter. Hum still there. 
5. Parasound service mentioned channel 2 is closest to the toroidal transformer and thus may have the most affect on hum. This is true and I would up rearranging the hum out of my fronts but it still present in my rears now where i switched them. Still audible from my listening position. 

Today I had a really weird thing happen. I was further trouble shooting and messing around. At some point the hum was almost "jumping" around. First I heard it in my Outlaw amp (runs my ceiling atmos channels). It sounded like it was coming from inside the amp itself. When I turned it off the hum jumped into my subwoofer. I don't know what I did but I just turned it all off and put it all back together. It went back to just hum in the 5 channels like it always was.... very confusing to me but suggests the issue is my system rather than parasound? @geof had mentioned this. I still have not tried removing the light dimmer from the line. 

Parasound does not really have any more to add and did state they would check it for me. I have to ship it to them (which I pay) and they would ship it back free. 

The dealer who sold it to me suggests I have to plug it into someone else's home's receptacle to see if anything changes. At 50+ lbs i'm not excited about this idea but i'd consider it......
helomech
1,680 posts
 
Is the hum present with the subs disconnected? 
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