Hegel hum?

Unfortunately I seem to have really dirty mains, had a H590 on demo, which hummed and then a loner H390 again hummed and finally my new H390 which again hummed, definitely DC issues which the Puritan drastically reduced (great equipment shame about the price). The H400 seems to have a buzz and I am wondering if its from the secondary small transformer and I am betting it doesn’t get the same mains feed as the main which has the DC blocker and is quiet. So now I think the culprit is the small transformer that I think is used to power sundry stuff. The unit was an ex demo and will contact the dealer but will give it a few days, maybe will ping Hegel direct. When I put my ear close to the amp the buzz is on the right side as you look at the amp from the front which again indicates the small transformer - perhaps it is picking up DC that the Puritan isnt killing. The H390 hum was the big transformer and the H400 is silent in that respect so am convinced its the small transformer. @baconboy do you think the buzz is the small transformer in your unit, mine is constant and maybe its just "normal" transformer hum

@dwest1023 

My 390 is dead silent. Even putting my ear right up on it.

Mine too...

@baconboy

Please contact Hegel and explain your hum issue to their technical support staff.

i also suggest you ask your retailer where you purchases your amp.  The hum issue needs to be addressed.  

My 390 is dead silent. Even putting my ear right up on it.

Received my H400 today to replace my H390, watched YouTube videos saying power supply now has a DC blocker built in. I had a lot of DC hum from the H390 but my Puritan PSM156 killed most of it. However the new H400 has a low pulsing hum which I am surprised to hear given what was said in the reviews, one of which said it was now dead silent (the Canadian guy Mr Chibbs I think) It is odd as it pulses and can be heard in my dead silent room. It is plugged into the Puritan but even on a normal mains socket still the same low level hum. Have played it only for a hour or so and the improvement in sound is apparent over the H390 but quite annoyed that it still hums. Seems a couple of people in this thread have the same issue? Dave543210 is describing exactly what I am hearing so maybe they haven’t made the H400 silent after all, sigh…

dave543210 Very interesting info. Thanks for sharing.

I recently bought a Hegel H400 and have also experienced a slight hum, normally not audible from more than a foot or so away, but very occasionally it's just loud enough to hear a very low-frequency hum from my listening position. A DC blocker hasn't helped. Apparently, this is completely normal for a Hegel when the power supply is sub-optimal. Their own website has the following info: 

If you are hearing a mechanical hum from the transformer and this also varies in loudness, it is nothing wrong with your amplifier.
Hegel amplifiers have very large unwrapped toroidal transformers. Unwrapped transformers are more prone to picking up electrical interference. Still, we have chosen not to isolate/wrap our transformers, as this would seriously degrade the sound quality of our amplifiers. The humming noise does not harm the amplifier in any way, but it can be annoying.

What you are hearing
The noise you hear is the vibrations in the windings of the toroidal transformers. Imperfections in the copper wires allow the windings to vibrate. We, of course, use the best quality copper and production methods in our transformers, but on a microscopic level, the wires are still not 100% round. That means that even if the windings are completely tight, they can vibrate, and make this humming sound.

Where does the noise come from?
It's the transformer that picks up other sources of noise on your home's electrical system. Typical culprits are products such as induction stoves, fridges, adjustable lighting, heaters, etc. These create an uneven load and thus generating DC back into the electrical system, something the transformer in the Hegel can pick up.

How to solve it
If you hear this hum try to troubleshoot by removing all other electronic components from the mains circuit the amplifier is connected to, to see if the sound disappears. If you can’t find the culprit you can use a DC filter/blocker between the amplifier and the mains outlet. This will remedy the problem.

all transformers humm, some very much so. Usually they are bolted in tightly, or have some elastomer in the bolt to quiet the humm. 

You may have an issue where the transformer has loosed up, and is being allowed to vibrate. If it has elastomer it might have been squished out, deformed, or come apart. 

Pull the amp out, disconnect from everything, pull the case, and see if you can move the transformer around. Also check to see if anything holding it down is loose. If it has elastomer, it should be "tight" but not so much so that the elastomer disformed too much, or gets pushed out. 

It's like a 10min fix, also normal.

My solution to the nest of wires (I have the Hegel H20 amp) is to seperate all interconnects and speaker wires from AC cables. I put that black foam pipe insulator with the slit in the middle  (cut into several pieces) to seperate all the low power interconnects/speaker wires from AC cables, just slip it over the interconnect and AC cable, cheap and effective.

Sounds like either a combination of cables picking up AC and/or DC gettting into your power lines, several products out there to clear up DC on power lines which make transformers hum as many have noted.

Your system is deserving of power conditioning, I like the Puritan PSM136 conditioner with groundmaster and some Verifi audio plug in thingies, astounding how much improvement that comes from cleaning up the power.

My experience with high current Class A or Class AB designs with large power transformers like Krell and Classe is that they normally produce a faint mechanical hum when first turned on as transformer charges and “warms up”.  The hum should not be audible after warmup.  I am not familiar with Hegel in general, but the H400 specs indicate it is a high current design with a large power transformer, so some hum on warm up may be expected.  You state this occurs after warm up. This does not appear to be normal.  I would contact Hegel for recommendations. 

It does not appear you are hearing the hum from your speakers.  If you are not hearing it from your speakers I would not expect it to be  ground loop hum.  If you are hearing it from your speakers, I agree with others to experiment with removing ground loop hum. See the link below that explains ground loop hum and how to attempt to remove it.  If that does not solve the problem, then contact Hegel   

https://www.sct.com.tw/articles/4-effective-approaches-that-eliminate-ground-loop-video-audio-interference

I've had preamps and amps that were sensitive to DC on the line before.  I've tried many DC blockers and pretty much all of them hurt the dynamics.  The one that I found to work best and not hurt my system dynamics is the Emotiva CMX2 AC Line Filter With DC Offset Eliminator.  It is a great design and does what it needs to do, nothing more.  I have one extra used one with the LED lights not working (a common reported problem) that I could let go for $75 plus shipping if you are interested.  My new Atoll IN200 evo integrated does not hum at all in the same house and location.

In fifty years of owning high end audio equipment I have never heard a hum coming from any of my components. 

You may try to contact Hegel and explain to their technical support staff this issue..? I would return such amp to manufacturer, if no help etc.. Foot away hum isn’t good, few inches could be okay..

I had many amps, and the only accuphase designs have zero transformer related hum noise. some transformers can be fixed by potting them in qualified epoxy, or putting transformers on shock absorbing spacers.

As the OP I offer thanks to everyone for their suggestions. I’ve never spent this much on a stereo component and was hoping for some assurance that nothing was amiss. From now on I’ll resume my listening position and enjoy the music.

Props to all who responded above. Very thoughtful and correct advice.

If you’re not hearing a hum/buzzing from the speakers your concerns should be minimal.

The Hegel integrated amps don’t turn off/on. They switch between standby (very low power consumption) to on (full power & ready to rock)

When transitioning between standby and on the system will fully saturate with current. In so doing the first thing in the chain which is that large transformer will charge up. Charging up is a physical process where the transformer’s copper wires wrapped around the core can micro-vibrate and can cause noise (hum).

This process should stop and the unit should be very quiet after warm up. If the hum persists, then as described by the proper comments above, there is some order of DC imbalance.

If you’re not hearing it from the speakers and can’t hear the physical hum from the amp at your listening position does it matter? I hope you enjoy your listening experience.

hum out of speaker indicative of ground loop 

hum out of box indicative of DC offset causing toroidal vibration

hums are annoying. You might try a DC filter ...ala,

https://avahifi.com/collections/accessories/products/humdinger-dc-line-blocker

Seems most audio systems are enjoyed having your ears equidistant from the speakers, rather that a foot from the amp 😉

My Hegel H590 has a normal, cyclical, mechanical, ever so slight hum.  In over 25 years in high end audio, I've never owned an amp, whether it be tube or SS, that didn't have some kind of a hum.  Some hums extremely slight, and some more noticeable.  With my Hegel H590, the barely noticeable humming sound cycles out after a few minutes.         

The hum is most likely coming from the transformer inside the amp. I use to hear it in my H390. Got a DC blocker and the hum went away. Since grounding the outlet the amp was plugged into I don’t hear any hum. I think what you are hearing is normal. I just purchased a Electrocompaniet intergrated and if I get very close to it, I can faintly her a buzz coming from it. No worry.

I should have also mentioned in my first post that the hum is not coming from the speakers. In fact, when I turn the volume up and pause the music, I hear nothing out of the speakers. It's the h400 that has a slight, even tiny hum. When I look behind the amplifier I have a spaghetti plate of wires between speakers, electric plugs, a streamer and a subwoofer but the hums not loud enough to make me try sort that mess out.

If you put your ear a foot from the speakers it is common to hear a faint hiss. But not a hum. This could be a faint ground loop. This would be that the amp is on a different circuit from the rest or one piece of equipment and there is a slight potential. 

To test. Plug everything into a single circuit and see if it remains. 

Is the hum mechanical? 

If so it can be related to DC in your AC.  Try turning off every other breaker in the home to try to locate it. 

I would think and hope no hum is normal and desired.