Slight hum in my amp. Is this normal?

Just had my Levinson 23.5 serviced by an authorized Levinson repair center with many years of experience, capacitors were replaced not the big blue capacitors the medium smaller ones on the board 680UF 100V and other small transistors and resistors, there is no hum from the speakers at all, dead silent but when I opened the cover to look at the repair I place my ears on top of the amplifier I hear a slight hum you have to get really close to hear it. I assume it is normal maybe one day when I can afford a new amplifier I will have something to compare but I am happy with the Levinson 23.5 don't have any desire to replace except for a Levinson 33H.

***UPDATE***
My Anthem A5 will be here Friday but one caveat, just picked up my (new to me) Anthem P5 from UPS. OMG is it a BEAST! Holy crap, it's 130 lbs and just connected it up. This may not be the place for a review and I cannot articulate like the pros, just sharing my latest events. The Integra 50.3, my spare unit had to pacify me while the A5 was traveling from Los Angeles to Ontario Canada, it's birthplace. Sure it didn't sound anywhere as good as the A5 and as I yearned for it's return, fond this P5. Of all places, Craigslist. It came with 4 Audioquest Diamondback XLR cables. Why not 5 is a mystery. I'm not crazy about the Diamondbacks because they look like very early versions with choke type strain reliefs that clamp/screw together. In addition, a pair of Transparent Musicwave Super speaker cables, 12 ft length. These things are HUGE! Im curious to how they will sound compared to my Audioquest Type II speaker cables. I think I'll keep the Integra as a spare and put the A5 up for sale. I hate to since it's in near mint condition however, I'd say the P5 is a nice concession. Wouldn't you?

Just received the service report. All of the power supply capacitors (they look like long C-cell size batteries) needed replacing. It's like a new amplifier now. I understand the caps are what fails soonest in most cases. Funny thing, I just purchased an Anthem P5 that will probably replace this A5 and if so, will be up for sale....

Sounds encouraging! Think I'll roll the dice and see if Prima Luna can fix the hum in my unit.

***UPDATE***
Well, my Anthem A5 made it to its birthplace safely and today I had a conversation with one of the customer service reps. Sure enough, there WAS a problem. Replace a couple bad capacitors. I don't have the hard copy report yet but I'm glad they DID find a problem, confirming I wasn't imagining the "buzz", "hum", or whatever!
As soon as I get the full report, I will list the problems here.
Also, I located an Anthem P5 for a killer price that will be replacing this A5 so it will be going up for sale if the P5 checks out healthy upon arrival. STAY TUNED !.......

Thank you blindjim,
I’ve done every test I could come up with. The best isolation scheme was to only have the Anthem A5 connected to the speakers with no other component connected or plugged into house power. The hum was audible from the amp and coming through the speakers. The the Anthem was replaced with it’s predecessor, an Integra 50.3. With the Integra, no hum what so ever!
why does a $4000.00 amp hum yet a "consumer" grade amp is dead quiet?
the Anthem A5 is currently en route to Canada. I'll have a report in 2weeks or sooner. In the mean time, I'm having two 20 amp dedicated circuits installed so the amp will have plenty of power available.

Hi

Hoefully all is well, but FYI…

I had a similar issue with a very late model, one of the last few made, BAT VK 500 WBAT pack SS amp some years back.

One of the two amps within the chassis had a hum when initially energized. Noticeable. Easily. Within 10 to 15 mins the hum lessend and lessend to near inaudibility within an hour. If you got right on top of it after then you could hear an ever so slight humming.

An ancilliary ground loop made it more e exasberating. Fixing the ground loop did not fix the humming along T former in one of the two amps though. Calling BAT and talking with Victor K his input was something loosened up up inside the channels T former. Somehow. Somewhere.

Victor also said, ensure your gear is on the same phase.

I had several dedicated power lines by then. Still, it hummed.

The hum never intruded into the audio. There was a bit of hash one could hear if immediately next to one of the loudspekars, but a foot or two away and it too was inaudible. Bacon sizziling sort of sound. Grunge on the power line. Adding in some passive PCs helped… but once more did not entirely irriradicate the hum or hash at the squeakers tweeters.

Nothing seemed amiss during listening sessions. The presentation was exceptionally good. Outstanding in fact, and I was running the big VK500 single ended from my preamp… not balanced by then. Formerly, it was being run fully balanced yet still the hum was present then too.

So the proposition was to pay round trip shipping to BAT, or something then close to $180, or live with the humming T former.

As it was not affecting the audio, I kept it for a while longer.

It was then the best sounding rig I had owned. So, I sold it all off and began building another one exclusively with tube monos instead of SS power. Smart, huh?.

What I’m saying here is this…. Unless something is actually affecting the presentation, an outage, audible noise as with a ground loop, its gonna come down to just how pedantic one truly is about their outfit. If I could hear buzzes, or hums from my listening position, I’d have to get it fixed or get rid of it, if I could NOT hear anything from the LP, so what?

As its in an older home with an older home’s wiring there are tons of areas for electrical issues, provided it ain’t in the amp.

If you have hopefully a breaker box and not a fuse box, What I would try is:
1. Switching off every breaker except for the one (S) supplying power to the outfit.
2. have someone then switch each breaker back on and see if there is any change whatever as to hum from the amp, or noise at the speaker (s).
3. naturally, if with all breakers OFF and you still have hum in the amp, and or noise at the speakers with the volume dead low or mutted, then its time to send the amp off to Misassaugua NY and let Anthem check it out.

I’ve had to do that too with an Anthem Processor I owned some years back. They are great folks, but do keep in contact with them so everyone is on point during the assessment and or repairs, so it ain’t sent back with the same issue. My pre/pro came back with the same prob and had to go back again, but then better communication finally resolved the issue which was two fold on my end and one with the pre/pro. My TV provider, my home wiring and an firmware update or reconfig with the pre/pro.

Hopefully, your amp doesn’t weigh 140 pounds shipped.

Best of luck.

No, my system is not connected to a cable box. I've given up wanting to use this amp with my Klipsch. Will trade in for a Pass Labs XA25 SS amp ( I tried selling here on A'Gon but couldn't get a decent price).

Is your system connected to a cable box or satalite dish via RCA interconnects? Sometimes the cable companies don't ground their outside connections to the home. This can cause a hum that will heard through the speakers. 

N

@jea48 - It sounds most like your last link. Does the PL integrated have separate tubes per channel? Or could a single tube cause hum in both channels?

dweller,

Does the integrated amp hum with nothing connected to any of the inputs?

Does the hum sound like this? 60Hz.
https://www.youtube.com/watch?v=SVZ2P0KsLic
https://www.youtube.com/watch?v=Lnd57eOyesk
.

Or like this? 120Hz.
https://www.youtube.com/watch?v=pC4Uzt0qm2E
.

Check this out. A tube causing a 60Hz hum?
https://www.youtube.com/watch?v=GrVtX0QGNls

I’ve worked with the national distributer trying most of what you suggest (cheater plugs, with source, without source etc.). The only thing I haven’t done is unplug everything in my house. I’d bet green money that the integrated is the source of the hum. My Balanced Audio Technology integrated is silent using the same electrical circuit. The noisy amp is under warranty. It works well with normal speakers so I may try to trade it in for some quite tubes or the new Pass Labs 25 watt SS amp. Thanks for your concern and advice.

The hum in my Prima Luna Prologue Premium integrated sounds like a constant 60hz. It is in both channels equally, Its amplitude is not affected by the volume control and muting the amp does not make it go away.

Now that sounds like a typical ground loop hum.

For the test below feed all the associated audio equipment from only one wall duplex receptacle outlet circuit. You can repeat the test later if you have more than one circuit you are using to feed your equipment and then check for hum again.

First disconnect all the source equipment from the inputs of the amp. With nothing connected to the inputs of the amp check for the hum.
(I assume the amp uses a 3 wire grounded plug and power cord).

No hum?

Add/connect one piece of source equipment to the amp’s inputs. Check for hum.
(In most cases the source equipment will use a 3 wire grounded plug and power cord that may be causing the ground loop hum).

Hum?

Disconnect that piece of source equipment from the amp’s inputs and then try another piece of source equipment and connect it to the amp’s inputs. Check for hum.

Hum?

If yes, good chance it is the integrated amp causing the ground loop hum problem.

If no hum, then it’s a good chance it is the first piece of source equipment you connected to the amp’s inputs.

Try all other pieces of source equipment and check for hum.

If no hum, then start reconnecting the source equipment, that did not cause the hum, back to the amp one piece at a time to the amp’s inputs checking for the hum.

If by chance you have a CATV cable box or a SAT dish box connected to the audio system in anyway start there first. Disconnect the incoming coax cable from the receiver box.
This a prime suspect for a ground loop hum problem. What happens is there is a difference of potential, voltage, from the incoming coax cable shield and the safety equipment ground at the wall AC power outlet. In most cases the coax cable shield is not ground properly outside at the grounding block on the outside of the house.

The hum in my Prima Luna Prologue Premium integrated sounds like a constant 60hz. It is in both channels equally, Its amplitude is not affected by the volume control and muting the amp does not make it go away. My guess is that it's coming from the rectification circuit or some shielding did not get installed during manufacture. I bought it to power some 105db speakers. It is useless in this application. 

For those who have offered advice, education, and information, I am very thankful. I've tried everything almost imaginable to find the source of the "hum". I've deduced the problem to it's source being my original assumption. Doubting myself provided a lot of experience and I'm sure useful education for myself or someone else one day. I decided to send the amp to the factory where the technicians who will repair my amp work on only one brand, the one they specialize in, their own!

The shop did not reply to my email. I became more upset by the hour and decided to send it back to its creator who will surely find and fix the problem. Stay tuned as I will surely post again when my Anthem amp returns and is functional again.

Lesson to learn here; don't take a Ferrari to a Chevy mechanic!

Not likely to be DC on the line, but if you think it is, I have a PS Audio Humbuster I can sell you which did not solve my problem. For toroidial transformers, the mounting position is sensitive to hum, try rotating the right tranny around its axis for minimum hum, and the tightest position of the mounting nut may not be minimum hum. You can also order polymer washers from Herbies to better damp the hum, If the Anthem is 15 years old, it may also be the filter caps which may need to be replaced.

After all this, my problem isn't a ground loop, bad ground, or anything external. Reading my email to the repair shop will explain;
Hi Morris,
Ok, I’ve exhausted my resources and have isolated the problem. I have a dedicated AC line I tapped from that powers my tankless water heater. This is a new line installed about 4 weeks ago and the water heater is the only thing powered by it so I ran an extension cord to the Anthem. The only connection after the Anthem is speakers. No input connections what so ever. The “hum” is in the amp AND audible through the speakers, all 5 channels.
I still have my Integra DTR 50.3 and for giggles, unboxed it and connected it. Again, AC line into the Integra and speaker wires to the corresponding speaker. Result, DEAD QUIET! I went a step further and connected the Integra to the wall (not the dedicated line), same result. Another step further and connected the AC line to the Torus, Torus to the Integra, Oppo BDP-103 Blue Ray to the Integra, speakers connected. Again, DEAD QUIET!!
My comparison is a $700.00 Integra AVR to a $4,000.00 Anthem amplifier.
Conclusion; there is something going on internal to the Anthem. No question about it. It’s something common to all 5 channels.
Lets review the chain of events….
When I lived in my condo, you serviced the Anthem and it worked beautifully! Had there been a “buzz”, I would have noticed. I’m POSITIVE of this!
I moved to this house and upon installation, I found the Surround Right channel dead, so I brought it to you. Then technicians finding was everything was good. Considering the contradiction, you recommended the technician disassemble and reassemble the amp.
Up to this time, I never heard a “hum” from the amp. Again, I would have noticed it.
As soon as I got it home, connected everything, I heard the “hum” immediately and brought it back. You called me and said there were no problems and I took a leap of faith doubting my own observations. I’ve never heard a “hum” from an amp before. You stated all amps have a little bit of noise if you put your ear close enough. I wondered why I could hear it from my seating position. Were my ears that good? Possibly but, thats when I put my ear close to each and every speaker and discovered the same “hum” from the amp, I heard coming from each and every speaker.
This is when I brought it back to your shop. In addition to the “hum”, the right side front panel ear was loose which got fixed.
Immediately when I put it back in the system, the “hum” was apparent and I tried to describe it best I could. Again, doubting my own judgement, I gave it a day or so. I came to the realization that what I was hearing was not normal.
It all became real to me today when I put the Integra in the system! To add icing on the cake, the technician neglected to install one of the housing screws and your office lady, had to mail it to me. It arrived today and I installed it.
Morris, I’m at a loss on what to do at this point. It’s clear the amp is not functioning properly. A piece of gear of this caliber should be light years better than the Integra it replaced in my system, and it was, until the technician disassembled and re assembled its innards.
I need to know how we are going to address this. I’m very upset and exhausted at this point and ready to send it to Anthem in Canada. Before I do, I need to know what you can offer for a solution. I know this will get resolved, the question being by who and at what cost. I’ve thrown a lot of $$ at this already.
Thank you and I look forward to resolving this expeditiously.

I tried a different power cord. If it were a ground issue, wouldn’t running it through a power conditioner such as the Torus correct it? Also, the Torus is plugged into the outlet by the left channel and I tried plugging directly to the outlet by the right channel. And the electrical connection is a two wire AC connection to the power source.

oldschool1, I can't remember.  Did you ever try a cheater plug just to see if it eliminates the hum from the speakers?  Not to use permanently, but to narrow your investigation?  In any case good luck in finding the issue.

Picked up my amp today and at the shop it seemed dead quiet however, there's ambient noise in the shop. According to the owner, early in the morning he heard nothing. It was dead quiet. After getting it home I spent the evening re configuring all my wiring taking care no power came in contact with any signal wire. here are my results as I emailed the shop owner:

Hello Morris,
It’s about 10:20 pm and everything sounds great however….
Remember I said that the “hum” could be heard from 10 ft away? Well I just unplugged and powered everything off one thing at a time and here’s my findings; What I can hear from 10 ft away is coming from the speakers. Yes there is a very slight “hum” in the amp and it’s also coming from the speakers. If I disconnected the interconnects from the preamp, no change. Of course since the power is off on the preamp and no signal feeding to the amp. Then I disconnected all the speaker cables and yes there is a “hum” or “buzz” in the amp. It has to be very quiet in the room to hear it.
This “hum” or “buzz” is not only in the amp but sending it through to all 5 channels. this explains why I can hear it from my listening position. I have a surround sound “hum” or “buzz”. So yes, the “hum” or “buzz” is in the amp and the amp also sends this noise to the speakers, all 5 channels. Could it be a bad ground causing this? Again if its the ONLY component with power connected, how could that be? Btw, there is no other electrical device on in the house other than an incandescent lamp for light. I tried powering it straight from the wall, using the Torus TOT MAX, and straight from the wall with a Emotiva CMX-2 Precision AC Line Restoration and Common Mode Filter System without the Torus.
I can only suspect it’s a component in the amp that is defective common to all 5 channels.

Any ideas anyone?
As a last resort, I will send it to Anthem in Canada. Being a current item, they will have all the components to trouble shoot with. It's just expensive to ship from California to Ontario, Canada. May be my last and only option.

I explained again that it was loudest when you first power it up then the hum diminishes after a few seconds but is still audible. He wants to keep power applied to it and observe.
Another thing I just remembered and haven't mentioned, since the hum began, it has been running a bit warm even at low listening levels when it was in my system.

Its 100% normal for any toroid to make a bit of noise on startup. This is because the core of the transformer can become magnetized when the unit is turned off. The next time its turned on, the magnetic field causes saturation in the core and the transformer rattles until the magnetic field is degaussed by the alternating current.

The second paragraph above suggests that the bias of the amplifier is high- which could account for the additional mechanical noise.

I have a modwright integrated KWI-200 that developed a hum that got louder over time. I finally had to send it to them and they replaced the transformer.
if this is a new problem since you moved, I don't believe in coincidences. 

 I was having the same problem a little while ago where my amp started humming. I tried multiple things without success but later I found that the problem was being caused by a potable heater connected somewhere else in the house.

if you ground is not isolated everything that is connected to the house is picked up by some of your components.

in my case that's all it took to get it fixed.

Hope this helps.

Adalberto

have experience with this one.  DC is in your line.  It not only can cause hum from the transformer, it can damage it (AND WARRANTY will not cover it) if you use it like this over time.  Bought a DC filter from EMOTIVA,  around $100 as I recall.  works like a champ!!!
SILENCE.   My humble opinion.  a great product for the money

I had the same problem with an Ayre V3 amp. I first built a DC blocker and that did not help so i removed the transformers that were humming and took them to a motor shop. They were dipped in that special winding varnish and when i reinstalled them they were dead quiet. What happens is that one or more loops of wire loosen up and then the magnetics cause the loose wire to vibrate. By locking them all back together it solves the issue.

There are two issues being discussed in this thread:  the original issue of a transformer hum and hum coming out of speakers.  They are two separate issues.  The transformer hum is mechanical, the speaker hum is electrical.  Hum out of the speakers is caused by one or more ground loops in the system.
Mechanical hum is caused by other issues, typically:  a DC offset in the AC line; electrical noise in the AC line; a poorly designed or implemented transformer; or an old transformer. 
I have three essentially identical amps that are about 25 years old.  The transformers in them did not hum, at least audibly, when they were new.  Now I can hear them from across the room.  Everything I read indicated that since the noise was constant and occurred with no fluorescent lights on and no motors running that it was caused by DC on the AC line.  As it happens, I built these amps at a company I used to own.  I consulted with my ex-partner, the design engineer and he said he doubted there was DC on the line and that the transformers, which are toroidal, were probably just old and the windings had loosened slightly.  I decided to build a DC blocker anyway.  It didn't help.  I tried an isolation transformer.  It didn't help.  I then built a fixture to measure any DC offset on the line.  What do you know, it was zero.
In the end, I moved the amps to the room behind the front listening room wall.  All's quiet on the listening room front.
oldschool1 - I suspect the right transformer in your amp is humming louder because the bias on the right channel is slightly higher.

My amp has been at the shop since Wednesday and the owner called me this morning at 7:00 am when the shop was dead quiet. Said he did agree the transformer on the right was a bit louder than the left however it was a normal hum. I explained again that it was loudest when you first power it up then the hum diminishes after a few seconds but is still audible. He wants to keep power applied to it and observe.
Another thing I just remembered and haven't mentioned, since the hum began, it has been running a bit warm even at low listening levels when it was in my system. Another thing is this whole thing only began when I moved into this house with knob & wire electrical. It is on a 20 amp circuit.
All of these things suggest DC in the line. Just to review; all of the problems began when I moved in this house. First thing was the surround right channel was dead. The shop found no malfunction indicating a loose connection that suddenly worked when I delivered it to the shop. As a precautionary measure, they disassembled it reseated everything. When I brought it home is when I noticed the hum. After bringing it back to the shop, being told it was normal, brought it home and noticed it running warmer than normal and of course the hum was still there. Since I refuse to accept that its operating normally, its back to the shop.
Again with everything I've read, this smells of DC. Even a Torus TOT MAX made no difference. I just ordered an Emotiva CMX-2. I plan to call the shop tomorrow for status.
Anyone care to guess what the problem is?
My guess is; 1- there's a bad connection, 2- a faulty component (transformer), or 3- DC in the line.

oldshool1, 
I had the same problem to my Constellation Mono amp.  Amp checked and find nothing at the Constellation repairing center.  Checked with Shunyata Research, I used quite a lot electrical products from them, they said probably a DC on the main.  With a reasonable low cost for a try, I tailor-made 2 DC blockers (one for each channel), to which to ensure sufficient current serving the Mono amp.   No hum from amp anymore, and more importantly that would not affect the sonic performance. 

Is your system set up for pure stereo?  Or, are you connected to some video theatre stuff too?

If so....disconnect all the inputs from sources leaving only one source at a tine....cd, phono...etc.

I'm thinking you need to rule out groundloop.

^^ Yes- and that is what we are dealing with when the power transformer in most audio equipment is involved. Its best to block the DC prior to a transformer- otherwise you have to use a very sophisticated power conditioner!

Thanks, Ralph. To be clear, though, am I correct in believing that to the extent the asymmetry of the waveform corresponds to a 2nd harmonic component, neither a DC blocker nor a transformer would eliminate it?

Best regards,
-- Al

@almarg , that's true, and if you look at my initial post I mentioned that DC on the line can also be interpreted as a 2nd harmonic. Its pretty clear that filtering using a transformer is an inefficient method; a DC blocker is a lot cheaper!

FWIW, most of the time the reason for DC on the line is an issue that is pretty closely associated with the local AC situation. For example, if there is a distribution transformer serving five houses, only one house might be running a space heater at half power, but all five houses would experience DC on the line.

Atmasphere 5-24-2017
DC on the line occurs when 1/2 of the AC line (for example, positive going portion of the AC waveform) is loaded while the other half is not.

Space heaters or hair dryers on half power do just exactly that. So one half of the AC line can have lower amplitude due to the loading as a result.

But its still an AC waveform and so can travel through a transformer. But the output will still be asymmetrical. The asymmetry can be filtered out by a DC blocker which is a simple circuit consisting of 2 or 4 diodes that are bypassed by some large capacity electrolytic caps.

Ralph, I share Jim’s puzzlement about that. If a waveform that is asymmetrical above and below zero volts is sent into a transformer, I would expect that what would emerge from the output winding of the transformer is a waveform that looks similar (assuming that the frequency components other than DC are within the transformer’s bandwidth), but that has been offset up or down such that the zero Hz (DC) component is eliminated.

Best regards,
-- Al

atmasphere

But its still an AC waveform and so can travel through a transformer. But the output will still be asymmetrical.

Is it really DC in the true sense/meaning of the word? Does it build to a DC voltage and then fall to zero at each half of the waveform cycle? If so then I could see how it would pass though from the primary to the secondary winding of an isolation transformer.

Sorry for my ignorance. I am just trying to better understand what is going on.
I do know there are people that say that an isolation transformer will block DC offset on the AC mains from the secondary of the transformer. I personally do not have any personal experience whether it will or not.
I believe you when you say it will not. I also believe that to be the case from actual bench testing which you have done.

I know AC and DC can both travel in a circuit at the same time. And yes I know the DC can be blocked using a DC blocker allowing only the AC to pass though the circuit or another circuit.

I know a pulsating DC voltage source, such as a battery, can be transformed, for lack of a better word, but constant DC voltage cannot. (As long as the applied voltage is constant.) If a constant DC voltage could pass through a transformer then an output transformer on a tube power amp would pass DC to the speakers.
Jim

.

It's a beautiful unit and extremely well made (big, beefy power cord). I don't need it so may try to return. Thanks for the heads-up!

@dweller

Emotiva has a customer friendly return policy should you choose to go that route.

https://emotiva.com/help/faqs/return-policy

Received the Emotiva  CMX-2 which made no difference in suppressing the 60 Hz hum (clearly heard thru my KEF Q1 monitors 12 inches away).
No source was connected, hum did not vary with volume and mute button made no difference. I've given up hope of using this integrated with my Klipsch LaScalla IIs. I'll be content using my BAT VK-300se 150 wpc integrated which is dead silent. Sometimes you get what you pay for...

Go under chassis, remove the transformer screws, apply some blue tac or similar substance to the holes and re-tighten the screws. It will lower transformer noise.

For a well made amp this is not normal.

@jea48 , I thought I did. One more try:

DC on the line occurs when 1/2 of the AC line (for example, positive going portion of the AC waveform) is loaded while the other half is not.

Space heaters or hair dryers on half power do just exactly that. So one half of the AC line can have lower amplitude due to the loading as a result.

But its still an AC waveform and so can travel through a transformer. But the output will still be asymmetrical. The asymmetry can be filtered out by a DC blocker which is a simple circuit consisting of 2 or 4 diodes that are bypassed by some large capacity electrolytic caps.

@atmasphere thank you for chiming in on this thread.

.

atmasphere

You can have DC on the line and oddly enough, it can be passed through transformers.

Please explain.

You can have DC on the line and oddly enough, it can be passed through transformers. It could also be considered a 2nd harmonic as basically its caused by loading on 1/2 of the AC line and so the AC waveform can be offset slightly just as if it were riding on a slight amount of DC. The resulting asymmetry could be interpreted as a 2nd harmonic.

Its easy to correct with a DC blocker which is a simple and inexpensive device. DC on the line can cause the core of the transformer to saturate, causing it to rattle or hum. It can vary from one transformer to the next even with parts from the same construction run.

Grounding in the house has nothing to do with this problem even if its not DC on the line. So the age of the wiring isn’t the problem.

Transformers can be mechanically noisy on their own despite the best of intentions. Tightening a noisy part down won’t help and might make it worse. But sometime the part is causing something else in the chassis (like a cover) to resonate and it might be possible to damp that part. If you can only hear the problem when you are within 6 inches of the amp its not a problem. IME, most audiophiles listen to their gear considerably further from the amp they are playing :)

Getting quiet transformers is always an on-going challenge. Transformer manufacturers often don’t understand how important it is for the part to be silent and might sometimes skimp on a few core laminations or the like thinking they can save a buck. In the process they might loose the entire run as reject parts!

Good Luck!

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.

If the cause of the hum is DC on the line, it certainly should work. It can't hurt in any case, unless one considers the two blue status indicators to be "active" and thus draw some minuscule amount of current.