Luxman Class A Integrated Slight Buzzing Noise


I just purchased my first class A amp--a Luxman 550ax--from an AG member recently. I noticed this morning that when I get close to the amp while it is turned on there is a slight buzzing noise coming from the unit. If looking directly at the top of the unit it seems to be coming from the right middle of the unit. Doesn't seem to affect anything with my Harbeth speakers and I only hear it from a couple feet away. I was wondering if this is normal for a class A amp. Anyone with a 550 or 590 have this issue? Any ideas what could be causing it? I have it plugged into a Richard Gray 400 Power Center using the stock Luxman two prong JPA1000 polarized power cord.

Sources are a PC connected USB to a Fostex HPA8C DAC connected to the Luxman with Transparent Audio Link 100 RCA cables.


It is probably of no concern. You could call Philip O'Hanlon at the Luxman USA distributor On A Higher Note. He is a gracious gentleman and has a thorough knowledge of Luxman products.
Perhaps the bolt that holds the power transformer in place is loose. It could be from being shipped. I would check that out as I had a Classe' amp that did that exact same thing.
Most likely it is a mechanical noise from the transformer. Could be loose, could be from a slight amount of DC on the power line or could just be endemic to the particular transformer. It should not affect the sound.
I would personally take it and plug direct to wall...its possible that it wont cure the transformer buzz...class a amps do run a little hotter so ?....
Some transformers buzz in relation to incoming power conditions, and this may be what you are experiencing. I had an amp one time that buzzed when an outside safety light came on at night…buzz went away at 7:00AM every morning. I'd also plug it into the wall and see what happens before you check the transformer bolt.
Thanks all for your input. bojack, you may be onto something with your suggestion of incoming power conditions. I haven't been able to fully investigate and haven't plugged the unit directly into the wall yet but it definitely seems worse when I play music in the early morning. I'll look into it more this week. Again, thanks all for your help.

Hi Dave, I bought a 590AX March this year and went through a rather long ordeal trying to get to the bottom of what I believed to be an unacceptable buzz being emitted from the transformer, I ended up with a response from Japan. I'm willing to share the details if you're interest?
I should add that I actually called Philip O'Hanlon in March when I first discovered the buzz my 590AX was making. He was very helpful and indeed I would say a gracious gentleman, he suggested I check if there was a rubber mat underneath the transfomer, which there was, this also ruled out loose transfomer bolts, which were tight as could be prior to loosening them to check for the mat, outcome was the buzz was and is still present.
Deedo: I would be very interested in hearing the response from Luxman regarding your problem.

My Luxman 590ax amplifier has a very, very low hum but you cannot hear it unless you put your ear on top of the unit. My 590ax is connected to the Furutech e-TP80 that conditions the ac power only. See:

Based on the above posts, I believe there might be something in your environment that is causing your Luxman 550ax class A amplifier to hum.

I suggest you contact the Audiogon person you purchased the Luxman 550ax from. Did the unit hum for this person? If not, ask him to describe their environment to see what the differences are.

What power cord are you using? I suggest you try the stock power cord or another power cord. I suggest you connect the power cord directly to the wall. I owned another product (not Luxman) that would not power on correctly if I used a non-stock power cord. The unit worked perfectly using the stock power cord plugged directly into the wall.

You might also try a cheater plug. This link includes some useful info about amplifier hum and the use of a cheater plug. See:

It is possible one of your other audio units needs the cheater plug and not the Luxman? Does the Luxman hum if you move it to another room (away from your audio system)? It is possible something else (maybe a light) in your listening area needs the cheater plug?

I suggest you turn off all appliances and lights (within reason) and see what happens. You might consider calling a Luxman dealer and ask their opinion.

If you still hear a hum, can you live with it? If not, please contact Philip O’Hanlon at On Higher Note. He is the US Distributer and is very knowledgable with Luxman products.

Unfortunately, it is going to take some time to determine the cause and find a solution. Please keep us posted.
Hello Hgeifman, whatever the cause I think it’s safe to say one thing is sure, what Dave and I are most likely hearing is magnetostrictive noise -

"Audible noise is an effect primarily originating from the phenomenon of magnetostriction: the slight change of length exhibited by a ferromagnetic object when magnetized. The familiar “hum” heard around large power transformers is the sound of the iron core expanding and contracting at 120 Hz (twice the system frequency, which is 60 Hz in the United States)—one cycle of core contraction and expansion for every peak of the magnetic flux waveform—plus noise created by mechanical forces between primary and secondary windings. Again, maintaining low magnetic flux levels in the core is the key to minimizing this effect, which explains why ferroresonant transformers—which must operate in saturation for a large portion of the current waveform—operate both hot and noisy.

Another noise-producing phenomenon in power transformers is the physical reaction force between primary and secondary windings when heavily loaded. If the secondary winding is open-circuited, there will be no current through it, and consequently no magneto-motive force (mmf) produced by it. However, when the secondary is “loaded” (current supplied to a load), the winding generates an mmf, which becomes counteracted by a “reflected” mmf in the primary winding to prevent core flux levels from changing. These opposing mmf’s generated between primary and secondary windings as a result of secondary (load) current produce a repulsive, physical force between the windings which will tend to make them vibrate.

Transformer designers have to consider these physical forces in the construction of the winding coils, to ensure there is adequate mechanical support to handle the stresses. Under heavy load (high current) conditions, though, these stresses may be great enough to cause audible noise to emanate from the transformer."

From this information what I gather is -

A) My Luxmans transformer is emanating Magnetostrictive noise.

B) This Noise/Buzz/Hum/Moan manifests when -
1) A ferromagnetic object is magnetized.
2) A secondary winding is loaded.
3) Mechanical force between primary and secondary
windings occur due to 1 & 2.

B1)is a product of the degree of magnetic flux levels contained in iron core, keeping flux levels low is key to minimising transformer noise.

B2)is a product of the degree to which the secondary winding is loaded.

B3)is a product of the construction of the winding coils, i.e. adequate mechanical support helps handle the stresses within the transformer and therefore reduce Magnetostrictve noise.

So minimal magnetostrictive noise is a product of the sum of low Magnetic Flux minimises Magnetostrictive noise, a low degree of electrical loading & adequate mechanical construction of the Secondary to ensure enough mechanical support to offset noise between windings.

From this information a number of valid points can be raised with respect to the amount of Magnetostrictive noise being heard from an amplifier.

1) Noise is congruous to ferromagnetic objects when magnetized.

2) If iron core purity is not high enough noise will certainly manifest in the transformer.

3) Any residual noise that cannot be eliminated will be amplified dependant on how heavily the secondary winding is electrically loaded, as this has the effect of increasing stress on the transformer and of enhancing any fundamental stresses already exhibited by the iron core.

Note: I presume this is one reason some manufactures produce massively over specified transformers, to provide headroom for loading?

4) A transformer whose coils are not wound so as to offer adequate mechanical support, is likely to produce more Magnetostrictive noise than it otherwise would.

The article also says that the phenomenon of magnetostrictive noise is also recognised as the familiar hum that can be heard around large power transformers (which appears to be true in the case of my good friend’s 590AX who posted prior to me, 'around' being very close to or ear next to the device), the article doesn’t say several feet away, as in the case of my 590AX can be heard up to 8 feet away.

I have to admit that even low music played masks this noise, however with the volume just half way with nothing playing through my ProAc D20Rs (88.5dB) my 590AX is rather noisy, the hiss and distortion not unlike white noise (which is what I presume I am hearing) is very noticeable and is certainly very noticeable at full volume. However when music is playing once again this noise is masked. So should all of this detract from enjoying your amplifier?

Well there is the factor of using my 590AX’s headphone output with sensitive headphones >100dB, in between tracks a background hum is always noticeable and can also be noticeable at low listening levels, moving from low to moderate volume I can’t help but wonder if the music is being tainted by this insistent hum which I’ve been told is not an intrinsic facet of how my 590AX is designed but is in fact to do with the quality of my electric, but aren’t the two inextricably related? I am running an Isotek Titan but it appears to be inadequate in bringing my mains up to a good enough quality for my Luxman to bring the noise I’ve experienced down to an inaudible level.

I've also owned a 550All and a 550AX and both of those hummed a little but the noise was honestly negligible and very tolerable, but in the case of my 590AX I have to say it is bordering on intolerable, but when the amplifier makes music I’m distracted from the thing that niggles me about it.

My last point is with regards to the difference in transformer noise I’ve heard between the 550All/550AX and my 590AX and points B2 above, the 550All was stated in a review as having a transformer rated at 540VA vs 680VA of the 590All, a 25.9% increase in capacity for a 20 vs 30 watt 50% increase in power, which may account for my 590AX being nosier than either of the other two smaller amps.
Deedo: I understand and agree with your points above. My suggestions above were the only things I could think of that might help solve the hum problem. However, the fact that your Luxman 590AX can be heard up to "8 feet away" is, in my opinion, a very "serious problem".

If my Luxman 590ax hummed (like yours does) so that I could hear it 8 feet away, I would return the unit to my dealer and buy another amplifier (not Luxman). Based on your 590ax humming problems, maybe your Luxman 590ax needs to be returned for repairs. What is your dealer saying? Can you return the unit to your dealer and buy something else?

I have owned other high end equipment before that, unfortunately, had problems that I could not live with. In all cases, I returned the unit to my dealer and bought something else.

As a happy owner of a Luxman 590ax, that does not hum, it really bothers me that your 590ax hums. If my 590ax had a hum (like yours), I would return it and buy something else.

I would also call Philip O'Hanlon and discuss the humming issue with him. Based on this tread, it seems other 590ax units also have a hum. A solution is required (repair or return).

When my Ayre QB-9 DSD DAC stopped working, I immediately returned it to dealer who shipped it to Ayre for repairs (bad board to board connector).
Deedo: I just noticed you purchased the 590ax from another Audiogon member. Did the 590ax hum for this person?
No I didn't but Dave who started this thread bought his 550AX from another Agon member. My 590AX was brand new so it requires running in, possibly the buzz will soften as the amplifier plays in i.e. the transformer laminates will physically settle in due to the oscillation? there is no mention of this in the manual though, but hopefully this does happen.
No I didn't but Dave who started this thread bought his 550AX from another Agon member. My 590AX was brand new so it requires running in, possibly the buzz will soften as the amplifier plays in i.e. the transformer laminates will physically settle in due to the oscillation? there is no mention of this in the manual though, but hopefully this does happen.
Sounds like a DC offset on your power line. This article/review should be very informative. Don't bother following the wikihow link in the article. It is about DC offset in an amps output which is an entirely different thing.
It's the design of the Luxman Transformer. I have a 1968 Richard Allen (Sugden) A41 Pure Class A amplifier, the worlds first Pure Class A production power amplifier, which utilises an EL transfomer. It doesn't buzz, so why does the DC offset on my mains not affect this 47y.o. amp? For one the transformer's physical size/weight, at least, in comparison to it's 10 watt output is overkill, the Luxman on the other hand has a disproportionate sized EL transfomer, regardless of material quality or design technique, I suspect, in relation to the 580VA or so that Luxman's 590 amp demands of it, hence possibly a higher propensity for Magnetostriction occurrence. The Luxman integrated Class A (note: not Pure Class A) amplifiers sound pretty amazing, but the modular/plug+play build makes me wonder where the tangible value these amplifiers are. I'll add as a final point, why do Moon (a relatively young amplifier firm), Sugden (around 35 years after Luxman began), Audion (a valve amp manufacturer that use both EL and Toroidal transfomer's in their designs) and Krell amplifiers not buzz the way my Luxman does? I believe the answer can be found in my earlier post concerning Magnetostriction, which can be controlled for the most part by transfomer design.
Deedo--I have found your posts very interesting and illuminating. Transformer hum and buzz has, off and on, bothered me for years. All the way back to when I owned an Adcom 535 (long time ago). I had a big Nackamichi for about a day (re-badged Threshold), that also hummed. And a big Sony from the old ES line that didn't. I had concluded that it was crap on the line coming into the house, combined with the design of the transformer--i.e. that toroidals were a lot more prone to it than other shapes/designs (the Sony had EIs). I've steered away from toroidals for a long time, first with a Cary and now with an Ayre. (I discarded Plinius as an option because there was a lot of anecdotal evidence on line about humming.) The idea that it all depends on the size/weight, the materials, and the exact construction, rather than the basic shape/configuration, is something of a revelation.
I have about 200 hours on my L590ax. There is no hum whatsoever. I'm using an Isotek Acquarius for power conditioning.
Excellent detective work. My C-J tube amp has a bit of a hum when no music is playing. Some call it tube rush. I don't worry about it because it does not interfere or create issues when I play music. Does your hum become undetectable when you play music?