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Quatros, M5-HPAs, and a community challenge

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I bought my first set of Vandersteen speakers one week after I started my first legit job. I was 25 and I carried those 2Cis around the country over the next 25 years.

The upgrade started when I accepted that even though I had worn earplugs at concerts my entire adult life, I had lost a fair amount of the high end. I wanted more of what I could still hear. I called Randy Cooley of Optimal Enchantment, and he started talking about the Quatros, powered by M5-HPAs.

Plotting commenced.

I knew who I had to convince first. Randy set up a listening session for my wife and daughter. He said the subwoofers bring people a great amount of joy. They could hear that, so the speakers and amps on our official family home improvement project list.

When our hopes to remodel the kitchen and bathroom in 2021 fell through, guess what shot to the top?

The speakers came, curbside delivery, on a few weeks ago early on a Tuesday morning. A neighbor sussed out my predicament, and helped me lift them up the stairs into the house. Amps, interconnects, and speaker wire arrived over the next couple of days. I quit work early to set things up.

Dropping this amount of money, a large sum for me, on a system that I have been eyeing for years had a likelihood to disappoint. Expectations were so high. What would they sound like in my house when they were mine?

I then had the remarkable experience of John Lennon appearing about six feet in front of me. The song was "Happiness is a Warm Gun."

It was one of the more stunning experiences of my life. These Vandersteen speakers and amps are worth every penny.


On the right, a beautiful combo, with the amp on stilts.

Careful examination of the photo of amp/speaker right might lead one to ask, "What are those things doing under the front feet of that M5-HPA?" 

This leads us to the community challenge.

That one amp has a soft hum. The noise is from the amp, not the speaker. The other one, about 15 feet to the left, is silent. 

I talked to Richard Vandersteen about this. He told me about a possible improvement to the feet that is on the list at Vandersteen that might help with this. But in the interim, he suggested the Jenga block idea.

Alas, my kid's Jenga blocks did not help. I am open to any other ideas. I am happy to provide more details of what I have already tried.


 And on the left -- I decided to spring for an additional speaker and amp so I could listen to something besides the Back to Mono box.

Thanks to Randy Cooley of Optimal Enchantment for guiding me and answering my many questions. And, thanks to Vandersteen Audio, who have been the loudspeakers for my entire adult life of music. You are a great companion.

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Congrats on the new hardware. I have the same and mine are about a month old now. 

How far away from the amp do you have to be to hear the hum?  Can you hear it when music is playing?

I heard a small hum once, but only when I was sitting right by the amp, way out of the pole position.  I haven’t investigated since, and I am so pleased with the “black levels” of silence/quiet, I haven’t bothered since. 

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SITREP Community Challenge. 

It is not quiet in our house at the moment so this is pretty unofficial data. But, I can hear a tiny hum from both M5s when I am on my hands and knees and my ear is 8 inches or less away from either amp.  Beyond 8 inches I do not hear it.  

I think it’s minimal and acceptable. I can hear a very tiny, tiny hiss from the tweeters on the Quatros when my ear is less than 2 inches from them. Beyond 2 inches they are dead silent. 

I have mild tinnitus at 11 kHz, but this hum is much lower than that (maybe 60 Hz)  so I think my data is good.  I can ask wife to perform same test if that will help you. 

I am plugged into the wall but I am on a single, dedicated 20 amp circuit with pretty meticulous receptacles and wiring. I have dimmers in the house, but they are ultra high end Lutrons. 

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Thanks JonM for the SITREP. To answer your questions: My family and I hear it after about two steps into the room when the house is quiet, maybe six feet. Only the one amp makes audible noise. When I swap amps, the hum follows the one amp to the other side. The noise goes away if I bend over and pick up the amp, but I have found that is not a sustainable listening position. The consensus, if I understand things, is that it the magnetized transformer that is vibrating.  It is not distracting when in use. But because the purchase is recent, when I hear it when I put the amps into standby mode or during silence between tracks, it is a bummer. I made a recording and the hum seemed to be around 120 Hz, if I was reading the chart correctly. It sounds like your situation is better. Let me know if you have additional info or thoughts.

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I'll put my two cents in.  Just remember what I declared the value to be...

Transformers often tend to hum.  There's lots of reasons for this.  Some basic types are more susceptible to humming than others.  Even within a family and model, some transformers tend to hum more than others do.  It has to do with the tightness of the windings, if and how the transformer is potted, differences in the cores, and so on.  It just happens.  Lots of technical details.

So, there's that.

In addition, there's the effect of "DC" found on the incoming power circuit.  I put DC in quotes, because what that really implies is an asymmetrical applied AC waveform, which effectively causes a DC component on that waveform.  Transformers don't like that additional magnetizing current.  Again, some transformers are more susceptible than others.

How about a couple more clues:

  • If you swap amplifiers between channels, does the hum follow the amp?  - Oops!  You answered this while I was typing.
  • Have you tried turning off all the dimmers and other gadgets in your house one by one to see if the hum ever goes away or changes?  You might actually need to unplug some.
  • Is this a consistent problem every time you power up the amplifier?  By that, I mean every time you unplug it from the wall and then plug it in again.
  • Have you tried placing this amplifier on something squishy?  Not permanently - just for a test.   - Oops!  You answered this while I was typing.
  • Have you tried adding damping to the cabinet top, like, for example, a hard cover book?  Another test.  - Oops!  You answered this while I was typing.
  • Where were you on the night of June 17th, 1996?  (Had to throw that in.)
  • Did somebody already ask you these questions?

(OT: Based on your snazzy user name, you might appreciate that my wife went to college with Thomas Mariano and Ed Mann.  They were leaving pretty much as she was arriving.  Hasn't talked to them since.  But, as three degrees of separation goes, this one isn't bad.)

Edited by BKDad
Paths crossed in aether...
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Thanks BKDad. Appreciate the connection to Zappa.

Answers . . . 

  • I did swap amps, and the hum followed the amp.
  • I have not turned off and unplugged everything in the house. The closest I have gotten is 3 am one night when everything was off that we can turn off, including all computers and phones being shut down. Next time I am home alone, I will turn off all the other circuits in the house and see if that changes things. 
  • It is consistent -- I hear the noise whenever I plug it in and turn on the power switch on the back. The hum does not change in standby or play mode.
  • I put the amp on FORLRFit for one minute. That did quite the noise to where I have to be within, oh, three feet to hear it. I would not want to do this without being assured it does not screw up the ventilation. 
  • A book helps like the FORLRFit. I have the same concern about keeping it cool -- there are vents on the top.
  • I believe that day in 1996 I was trying not be miserable camping on Mt. Hood. I failed. 
  • You are first person to ask me most of these things.

The weird thing is the one amp hums everywhere I plug it in, and the other amp does not anywhere. Moving them around has been a good weight workout, though.

Thanks much for the ideas. Keep 'em coming.

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Hmmm...  (No pun intended)


  • Do you have any idea what you AC mains voltage is?
  • You probably won't know this, but I'll ask anyway:  Any idea what the AC waveform looks like?
  • Sorry about Mount Hood...

I hate to suggest this, but this could just be variations between units.  It could be that at the factory, with the AC mains voltage and all there, both units were quiet as church mice.  But, at your home, one amplifier may not be quite as happy with the AC waveform or voltage.

It does seem like the transformer is making the case vibrate.  Holding the amplifier in your hands makes the hum go away, and the damping helps, too.  If it was the transformer parts themselves humming, external measures like you successfully applied wouldn't have much effect.  At least, so I think.  

I don't have M5-HPAs myself - BKDad only pawn in game of life - but the pictures found in another thread on this forum show a lot.  It's possible that the covers might dimensionally change a bit either over time because of the amps not sitting on a flat surface, or due to shipping.  So, the mating edges might not be entirely flat against the cover.  This could allow any transformer vibrations to excite the cabinet enough so that you're hearing the cover vibrate across this small gap.  Perhaps some tape along the mating edges of the seams would be a fix.  Mr. Vandersteen would obviously be the one who could tell you that or offer ideas.  (Remember the two cents valuation!)  

I can't tell if the covers are aluminum or steel.  I'd only be guessing.  If they are steel, it's also possible that the external field of the transformer, however small it might be, is causing the cover to vibrate.  I've certainly seen that with other pieces of equipment, audio and otherwise.  Again, some kind of tape might be helpful, not only for mechanical damping but also to add magnetic gaps in the closed magnetic "turns" created by the cabinet.  

JonM's observation that the hum seems to be 120 Hz kinda supports these two ideas.


I only offer those ideas as things to consider in further testing at your end.  I'm sure that more information supplied to the factory would only be helpful, especially if they can't replicate the problem at the factory.  

Again, I'm just some guy on the internet spouting off.  Good luck!

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Thanks, BKDad. Hmmm puns make our 2 cents worth at least a dime.

On electricity, Sgt. Schultz comes to mind -- "I know nothing!" Here are some words that may make sense.

We have 200 amps coming into the house. I have a voltage meter on a backup battery that buys me a few minutes to shut down my iMac when the power goes out. It fluctuates between 119 and 123 volts. I have no notion of the what the waveform looks like.

We shall see what Mr. Vandersteen suggests. I am up for tape, better feet, and even acceptance and peaceful equanimity. So long as the hum does not get louder. 

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BKDad is correct, the transformer is what is moving.  Toroidal and R Core (what we use) transformers have high sensitivity to non-symmetry on the line (DC component) which causes the core to partially magnetize (vibrate).  Today our power is very noisy (solar inverters, wind generators, switching power supplies variable speed motors, dimmers, etc) many of which are mandated by the government for efficiency.  We chose the R Core because it has great regulation, low radiated field, efficient and runs cool but we deal with this DC power line problem and may be a better choice would have been an E & I core transformer (much more tolerant of a DC component).  E & I core transformers would have compromised the sound and that would not be my first option, but these line problems are not going to get better, so we are working on a solution.  We have found changing out the transformer is not a solution in homes where this is a problem because once line distortion gets to the point of causing a hum the margin is razor thin.  Changing out the transformer has less than a 50% chance of improvement and would be a very expensive solution and even if it lowered the vibration a slight increase in line distortion would bring it back.  The solution is to cap couple the AC going into the primary of the transformer which would block the DC component and silence the transformer but at a cost in sound.  It lowers dynamics and softens the bass slightly but still sounds better than using a E&I core transformer.  We will make this mod available in the future as an option for situations where the noise is not acceptable.  RV

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Here's some more technical information on this, oriented toward the audio enthusiast:


Ed Simon also published a series of articles on various aspects of powering audio gear back in the Ought's in AudioXPress magazine.




As you'll see when you read these, the problem is everywhere and the solutions all have their own compromises, even if it is just the complexity.

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6 minutes ago, GdnrBob said:

Is there any way to 'clean up'



Of course!

Cheap?  No.

Easy?  No.

Especially if you want to avoid collateral effects.

If you power your entire listening set-up with giant batteries, you avoid transformers...

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1 minute ago, Richard Vandersteen said:

The cover of the M5-HPA is already damped.  This problem is one that Damping Plates can not solve.   RV

Well...  If you build a shelf made from a Damping Plate just beneath the floor where the amp sits, put the amp on that shelf, and run the speaker cabling through the floor, that might mitigate the problem.  The transformer will still hum, but it would be in a different room.

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Thanks to everyone for batting around ideas and sharing your knowledge with me.

I am going to turn off all the power to my house, other than to the listening room, and see if the hum ceases. If it does, I will turn things back on, one circuit at a time, to see if I can find a trigger.

And, to be clear, the noise is not overwhelming. There are other ambient noises, so this is just another one, by no means the worst. My neighbor plays bagpipes. 

If the new feet come through and show promise, I will try those. And, if there is a eureka moment that solves this, let me know.

You have a great community here. You should all be proud.

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2 hours ago, Richard Vandersteen said:

The cover of the M5-HPA is already damped.  This problem is one that Damping Plates can not solve.   RV

Thanks Richard.  I thought so, but as you know, I'm ignorant on so many of the technical stuff!  

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Once upon a time, Richard Marsh designed a product for MIT (the audio company, not the school) called the MIT Z-Stabilizer.  There were several models, but the one of interest is the Z-1.

Here's a Stereophile review:  https://worldradiohistory.com/Archive-All-Audio/Stereophile/90s/Stereophile-1994-12.pdf  (Note that the technical information is really iffy here.  The description doesn't even match the patent.)

There is some somewhat more technical information on it here:  https://mitcables.com/filterpole-technology/

He even got the circuit patented:



Note that these patents have almost certainly expired by now.  There's schematics for the circuit shown on the patents.  So, this is where you want to go if you're interested in the details.

A circuit like this has the potential to fix this problem up, at least to some degree.  Perhaps you can borrow one to try to see if it helps.  Easy enough to install and try out...


Edited by BKDad
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I owned the Z1 back in the day.  I Bruce's top speaker and interconnect cables that were tuned for my tube gear and then also when I had the Spectral amps and pre amp for a spell.  I recently sold the music hose 770 speaker cables.  I forget which box designation they were, but man were they awesome in the day for my system.  The Z1 made such a positive difference as we lived in a condo and hte power sucked.  I also had Richard Marsh's amps for a spell.  Mono blocks.  Man were they a value.  Gave them to a family member who LOVED they for years.  What memories.  

It sounded best with the Spectral which I got rid of, because it was a bit too 'critical', lol... Had no soul for my set up and was worth way more than my top ProAc speakers of the time.  I broke even as I bought them used.  Dealer had them at a steal trade in price.


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