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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
lowrider57's avatar
lowrider57
5,393 posts
 
It's not acceptable to hear hum thru the speakers from your amp. It's possible that it's the grounding scheme of the Parasound, but before returning it, you need to check the grounding of your Hubbell duplex.
Pull the receptacle from the wall. Is there a metal box or plastic? 
Is the ground wire attached to a ground screw or a metal box? If using a metal box, the receptacle must be connected to it with a ground wire.

A ground fault tester will confirm proper grounding.
https://www.amazon.com/dp/B000RUL2UU/ref=cm_sw_r_u_apa_fabc_2A5ERAZ2Z0Y5P78X4C7T?_encoding=UTF8&...

Have you tried using a receptacle on a different circuit?


geof3
1,124 posts
 
Obviously no one is reading the post. The OP changed out three amps, all had hum, albeit to a different degree. So the problem isn’t the Parasound or any other amp, it is a problem with your power and the Parasound is more affected by it. Do you have any fluorescent lights, dimmers, led lights or other noise producing things on that circuit? Particularly dimmers... they are notorious. You could have a ground loop, you could have a faulty interconnect. Not an easy problem to nail down, start with any dimmers etc. they are the easy ones.
mofojo
2,171 posts
 
  If not too difficult do what I did. There was a teeny bit of drywall cutting involved but depending on your house layout may be easy peasy.

   Get dedicated 20a line from your box.

   Well worth the 500 it costs me . For sure. I had a small amount of static but could  not be heard from the seating position. After . None nada. Also it is better at higher listening levels when pushing things. Way more relaxed sound with better bass. I am knocked out by this 500 mod. My volume on dac to amp is about 6db higher on an everyday basis with 0 fatigue.  

jwl244 OP
64 posts
 
@yogiboy I was more excited about integrating the new amp into my system and with settings. I never noticed a hum in my system ever before. I can't say if there was hum before I changed the receptacle. I do plan to switch the receptacle back to stock to see however....

@helo thank you I was thinking the same thing and was really surprised tech support told me that actually. 

@lowrider57 the receptacle did have a ground which I attached. I do need to pull it off the wall again to make sure it didn't come loose pushing it through the gang box 

@mofojo thanks for that. I think mine is dedicated but I'm not 100% sure now..

@geof3 I do have dimmers around in my listening area. I suppose even if the light isn't technically on the dimmer is still working? I didn't think about this one. Might try and disconnect or cap off one of the receptacles 

I'll report back to the post when I have an update 

jasonbourne52's avatar
jasonbourne52
2,863 posts
 
Hum is not acceptable! That Parasound 5-channel amp has an internal ground problem someplace between the circuit boards and the chassis. The design team should have fixed this problem before production! Nothing you can do externally will fix it!
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