Slight hum in my amp. Is this normal?

Wow, I thought it was bad hearing hum from my Klipsch speakers from 12 feet. I'd be pissed if I could hear the actual transformers! I have an Emotive  CMX-2 ($127 w/tax) coming tomorrow. I'll report on its efficacy.

Today I dropped it off at the local authorized service center who has been the only company to work on my amp. Interesting thing, without opening the cover, I put my ear real close to the vents adjacent to the transformers, there are two, one on the left and one on the right just behind the front panel. I could swear the hum sounds slightly louder from the right side making the right side transformer suspect. I used an analog decibel meter using fast and slow response, and it's hard to tell with the slightest ambient sound pressure. It measured approximately 55 dB with the right side maybe 1/2 - 1 dB higher. Are my ears that good? the proof will be in the pudden when the shop gets into it. The owner said he would get in early when it's dead quiet and listen for the hum.
I told him today that the hum is loudest when power is initially applied then quiets down however, I can still hear the hum from 10 ft away when the room is quiet. Of course when a program is playing, the speakers drown it out so It's inaudible. My Integra DTR-50.3 AVR, $700.00 retail has always been dead quiet. Certainly a $4000.00 retail Anthem A5 amp should be as well.
Lets see what they say in a couple days. Stay tuned!

What jea48 said.  I just didn't want to be an accomplice if you touched the wrong place with your screwdriver.  Let us know what the solution was.

I was unaware (until I heard about it here and looked the damn things up) of the Emotiva CMX stuff, but it IS less expensive than the Humbuster III, and actually obtainable. Cool.

oldschool1,

Is this what the inside of the amp looks like?
http://www.studio-22.com/anthem/images/Anthem%20MCA%2050%20-%20Inside1.jpg

If so notice the two toroidal transformers on each side. Pull the top off the amp and check the center mounting bolt and nut for tightness. Make sure the round top plate is seated properly on the top of the transformers. Maybe one of them is loose.

After checking them, to make sure they are secure, power up the amp and listen to the two transformers. If the hum/vibration is still there listen to each transformer individually the best you can. First verify the hum is coming from one or both of the transformers. Is one louder than the other? If so recheck the mounting bolt and nut. Make sure the round top plate is seated properly on top of the transformer.

@gdhal,

An isolation transformer will not pass DC.

dhal,
I like the concept of what you and wolf_garcia suggest. Here is Los Angeles we typically don't have the same power issues one would have in other parts of the country however it couldn't hurt. Reviewing the chain of events, I seriously think it's a component issue and I know it's in the amp as it is not coming through the speakers. I'm going to exhaust that possibility first and then add the Emotiva. I like Emotiva products. I have one of their HDMI cables, a couple interconnects, and a power cable (AWG 12).

Here is a more detailed description of the events leading up to my evaluation. I posted this in another forum explaining its wording:

Yesterday I purchased a Torus TOT MAX. WOW, what an improvement it made to audio quality however, the "hum" is still there. This morning I got up extra early as it was very quiet in the room and outside so I figured it would be a great time to see to what degree this "hum" was. As luck would have it, I could hear the "hum" in my seating position 10 ft away from the A5, and it was running through the Torus. Correct me if I'm wrong but the Torus should have corrected the problem if it were a grounding issue. Here are the sequence of events leading to this problem.
-Bought as a used unit, damaged in shipping
-Took it to the only authorized Anthem repair facility in the US here in Los Angeles
-Repaired successfully and ran beautifully until
-Moved to a new home and the right surround was dead
-Brought it back to the service center and they found no issues
-Then they completely dismantled it and re assembled finding no issues
-As soon as I got it home, I noticed the dreaded "hum"
-I returned to the service center the following week and they plugged it in with no interconnects, only the AC power. We heard the hum. Of course we had to put our ears relatively close to the unit to hear. Problem was, there was ambient noise in the room so it wasn't as easy to hear. They said what I was hearing was perfectly normal. The skeptic that I am and never hearing this before, I had my doubts.
Now that I've tested it with the Torus, heard the same hum as before at home and at the service center and the fact I never heard it before, tells me there's something not right.
Today I sent an email to the service center asking what he suggests. Worst case scenario, I send it to Anthem Canada and get it corrected once and for all. They can expect a telephone call from me tomorrow discussing this and their suggestions. I know they are going to suggest sending it in, of course! They like the business. I don't mind the service bill, it's the shipping I have an issue with since its not exactly small or light weight.

@oldschool1

The Torus TOT MAX you bought is certainly a nice power isolation transformer. Thing is though, in the case of hum, that can very well be caused by DC on the line, and I don’t believe the Torus has a filter for that. For another $120 you might as well get an Emotiva CMX-2.
https://emotiva.com/products/accessories/cmx-2

I have one. It does work and even if it doesn’t in your particular case, it cant hurt. So essentially what I’m suggesting is use both the Torus and CMX-2. Torus plugged into CMX-2 of course.

wolf_garcia recommended a PS Audio Humbuster III. Same concept/functionality. That too would be good if you can find one, but is likely more expensive than the Emotiva.

Watching this post with interest. I have a Prima Luna integrated making hum. If you are successful getting your fixed, I'll send mine in (under warranty) to see if it is fixable.

jc4659, my guess is either you hit the nail on the head or it's a faulty component. Your suggestion is about the most logical given the history. Another thing I'd like to add, this unit replaced an Integra 50.3 AVR that was dead quiet. I don't believe this "hum" is normal and definitely not acceptable. I'll report the service centers response tomorrow. I believe they are a top notch shop however it's my assumption the tech may have missed something. Whatever the case it's gonna be fixed even at the cost of shipping from Los Angeles to Anthem in Canada and back.

I once had a subwoofer that had an internal hum.  It was actually more of a very faint buzz, but audible when it was quiet.  The manufacturer of the sub acknowledged that some of their transformers were noisier than others and they sent me some parts to install around the transformer that physically isolated it from the cabinet and the noise went away.  If in your case the service involved "disassembled and reseated everything" then I suppose it's possible that what you are hearing is resonance from vibration.  They would need to loosen and retighten the fasteners holding the transformer in place such that it doesn't resonate quite as loudly.  I just thought I'd share my experience since the solution for my issue was a physical one rather than electrical.

Thank you everyone for the great intell. I bought a Torus TOT MAX yesterday at a killer price and the dreaded hum is still there. I'm convinced its internal in the amp and something isn't right. This morning real early I powered it up with no input. Nothing else was on and I could hear a ver faint hum from 10 ft away.
I've sent an email to the local Anthem authorized service center, who told me this is normal, and we'll see what they say. As I mentioned before, there has never been a detectable noise (hum) from this unit until they disassembled and re assembled it. Worst case, I bite the bullet and ship it to Anthem factory at a hefty shipping cost.

Question for oldschool...if you've got 'knob & tube', I can only assume you don't have the 3rd prong 'direct ground' wiring.  That could be an issue, even if it's all wired correctly.  In order to use those wall plugs which Should be 2 prong only, you'd be forced to either use a 'dead man' 3>2 plug adapter at each connection for such, or been doing some 'plug surgery' and snipping off the 3rd prong.

In the first case, the 3rd is just hooked up to the normal ground.  In the second, you just 'sidestep' it, which does eliminate any common grounding between any and all chassis ground connections.

The 3rd dedicated ground exists solely for short-circuit safety issues, and it's what a GFCI depends upon in the modern kitchen and bath...to protect you from grounding yourself out if you come in contact with water if using a faulted device.  By extension it works for the balance of the home if, by chance, you're operating a faulty appliance or spill your drink on some device.

Now....given your situation, if there's no hum exhibited from any other device, within your system or without (a fluorescent lamp or some other device being run concurrently when you've powered up), and it ONLY exists from the one device that you've had refurb'ed, I'd look at a interconnect cable going into AND out of the amp.

I chased a 'hum' gremlin in my system not long ago, swapping power cords, power sources, interconnects on All components, hunting down a somewhat loud hum.  It finally came down to One faulty cable of a pair, which had either a bad RCA plug or a fault in the wire itself.

Viola', it worked.  To be honest, there is a slight residual hum from the amp if I crank it up with no program.  And a power conditioner may or may not minimize that, depending on (as noted) the design and parts used in your amp and other segments in the signal chain.

While I'm being long-winded and pontificating *G*, you might try hooking up the amp into a 'bare bones' setup....different speakers, one source, something really minimalist.  See if it still hums at you.  Dig out the 'orphans' in the attic, closet, or garage...hit up a buddy for an afternoon 'test', you spring for the lunch and libations...

Not that I'm not telling you to buy a power conditioner, but it'll save you the WTH response if it doesn't make a difference....;)  The last could be cheaper and maybe more fun and educational. *S*

I've always experienced power transformer hum and HF hiss until my current ARC and Hegel H30 amps.  Both dead quiet so I guess it's design dependent.

I don’t recall ever hearing it before. When I moved into a new home, the right surround was dead. I took it to an authorized Anthem service center, the only one in the USA, they couldn’t find any problem so as a preventative measure, they disassembled it and reseated everything. When I powered it up is when I noticed. Note this home was built in 1941 and still has "knob and wire" electrical. It looks like everything is grounded but electrical is not my specialty. I’m purchasing a Torus TOT MAX tomorrow so I wonder if that will help. I'm not sure if everything is sharing the same ground. If it were a grounding issue, wouldn't I hear it in the speakers? This is not coming from the speakers, only the amp.

I bought a now discontinued PS Audio Humbuster III to solve that issue and it did. Those things show up for sale here and there and something like that should be made by somebody else, but I’m not sure if that exists. Maybe as part of a good power conditioner.

Use a balanced power source and it'll go away.  A Furman, Euqitec, Tourous etc.  


Good Listening

Peter

Having spoken to a couple of manufacturers about their amps it seems that the use of low or zero negative feedback can leave an amp vulnerable to slight hum. 

I would not say it is "normal" but it is pretty common.  Both my Acurus amps emit a slight hum that is only audible at close distances.  Most likely transformer hum(vibrations) in the majority of cases.

Bill

Just some transformer hum not unusual. Is the amp new or new to you? Or if you've had it a while is this noise new?