McIntosh Transformer causing noise in speakers while disconnected.

[Golf]

It is known that the magnetic field from the mains transformer can be picked up by nearby speaker chassis. I had this at an Fender Combo guitar amplifier.

Maybe somewhere deep inside the McIntosh’s manual you’ll find something like this:

Make sure that your McIntosh MC255 is located at least 3.1415 feet away from any loudspeaker sets at any time.

And even more important: Don’t listen to folks trying to tell you that the drawing of a 40 Hz peak is actually that of a 60 Hz peak.​

 

[DonH56]

The sound that comes out the speaker is the product of the frequency distribution of the magnetic field generation (either low or RF frequency), the transfer function linking amp to speaker via EM fields, the transfer function of the conversion of EM field to electrical current in speaker, and the speaker frequency response. So there are a lot of steps that might de-emphasize 60Hz and favor 120Hz.

One of our hypotheses (from @tmtomh ) is DC current from the mains is causing saturation of the toroid transformer, and that this leads to the release of large magnetic fields that are picked up in the speaker. Saturation in a transformer due to DC creates a lot of second harmonics.

View attachment 357876
From Sarath Perera, Sean Elphick, in Applied Power Quality, 2023

I like this idea, but didn't mention it because significant DC would usually cause the transformer to buzz as well. Toroidal transformers are much more sensitive to DC offset than conventional EI types (no gap in toroids). A DC blocker could be worth a try...

Different comment: It looks like a conventional supply, so full-wave rectifiers would produce a strong 120 Hz component (and multiples) given a 60 Hz line frequency.

 

[Zapper]

I like this idea, but didn't mention it because significant DC would usually cause the transformer to buzz as well.

My thoughts exactly. But we can't rule out the possibility. Maybe 30lb McIntosh transformers don't buzz no matter how you abuse them?

Different comment: It looks like a conventional supply, so full-wave rectifiers would produce a strong 120 Hz component (and multiples) given a 60 Hz line frequency.

Another good point.

 

[NiagaraPete]

EDIT: **Amp is plugged into wall outlet using stock cable, as per manual - I switched to the high current isolated bank of the Panamax MAX5300PM, still noise, then used Blizzard AQ Power Cable, still noise, went back to wall and stock cable**
See pictures: What am I scientifically dealing with, and what are my options for placement or protection? Just installed new MC255 and B&W HTM71S3 to finish my 7 series 5 channel. When I turn the amp on, any speakers close to it pick up a lot of noise even when speaker cables are disconnected. I'm assuming the speakers are picking up (noise, magnetic interference, idk what is exactly happening..) from the Transformer. Is that normal with McIntosh and high powered amps, and should I consider replacing it to fix the problem? It seems the interference is omnidirectional from the amp. As you can see in second pic, I do not have many options for placement to keep it away from the LCR speakers. When I had it side to side next to the Center speaker in Pic 1, the noise was too loud to ignore.
View attachment 357490
Then I moved the AVR/PRE onto that little table and pushed the Center far left all the way to the edge, and it helped, but still noisy. The right Tower even picks it up a bit. Are there materials which will protect the speakers from picking this up? Anything I can put between them? Center needs to be in center, and the amp cannot go on the bottom (cats). Even if it could, it still causes noise from underneath the speaker thru the MDF.
Amp is in Panamax MAX5300PM High Current Outlet with Audioquest Blizzard power cable, and Panamax has NRGZ3 power cable to wall if that makes a difference.
View attachment 357491

I haven't read all the pages of posts but I can say 1) that amp shouldn't be turned on without speakers connected to it 2) the amp probably needs to be serviced. If its generating enough magnetic noise to be picked up by a speaker driver it's probably not healthy for you to be near it.

 

[Golf]

It looks like a conventional supply, so full-wave rectifiers would produce a strong 120 Hz component (and multiples) given a 60 Hz line frequency.

Wow ... Audition indeed finds a nice 120-Hz-pattern. But that seems to be based on 180 Hz as its starting point somehow:

 

[mhardy6647]

Call McIntosh's Tech Support line (607)723-3512 ask for Chuck Hinton(Tech Support) or John Messemer(Service Manager). There maybe other techs there that could help too.

Best advice in this whole thread! Get on the blower, @ClassG33 !

 

[mhardy6647]

In full disclosure -- because I think the phenomenon that precipitated this thread is very interesting -- I posted the basic question Somewhere Else (Polk forums -- again, I am all about disclosure ).
One of the stalwarts there offered a great suggestion in terms of understanding the phenomenon better (even though it won't really help @ClassG33 much if he's devoted to the B&W loudspeaker suite): If another kind (!) of loudspeaker is available in the house -- does another loudspeaker manifest the same effect or is it specific to the B&W -- maybe even to just the B&W center channel loudspeaker?

I do realize that not everyone runs a shelter for wayward loudspeakers as do, ahem... umm... I.
Still seemed worth puttin' out there.

 

[Doodski]

Maybe somewhere deep inside the McIntosh’s manual you’ll find something like this:

Make sure that your McIntosh MC255 is located at least 3.1415 feet away from any loudspeaker sets at any time.

And even more important: Don’t listen to folks trying to tell you that the drawing of a 40 Hz peak is actually that of a 60 Hz peak.

... with additional instruction in that manual regarding @Doodski getting a proper nights sleep to avoid looking like a bonehead and before doing silly stuff... sigh* LoL.

 

[radix]

Wow ... Audition indeed finds a nice 120-Hz-pattern. But that seems to be based on 180 Hz as its starting point somehow:

Inductive coupling, if that is what it is, will have resonant frequency(-ies) based on the inductors and capacitors of the two systems (amp and speaker).

The question is why is the McIntosh emitting so much. Maybe it's because there's no load? Maybe something is loose inside that's not grounding? Maybe something else is wrong.

 

[OldHvyMec]

The theory(s) is sound, the test method is solid, the fault is clearly defined, the effect is obvious and even more importantly it is repeatable.

So what was/is the answer? I've read a lot of "stuff" but I didn't read an answer. What is repeatable? He can make the noise
go away and then make it return? What did he do to make that happen?

Regards

 

[Doodski]

So what was/is the answer?

I have ideas about what your questions entails although I am not sure what you really want to know. Can you please ask in a different way so I can get more information? Thanksss

I've read a lot of "stuff"

I sure have read a lotta stuff too and I'm onboard with you there.

What is repeatable?

The fault is repeatable in that it can be recreated anytime and the same fault occurs when moving a speaker near the McIntosh amp that is not connected to any speaker with wire.

 

[mhardy6647]

Make sure that your McIntosh MC255 is located at least 3.1415 feet away from any loudspeaker sets at any time.

And even more important: Don’t listen to folks trying to tell you that the drawing of a 40 Hz peak is actually that of a 60 Hz peak.

... with additional instruction in that manual regarding @Doodski getting a proper nights sleep to avoid looking like a bonehead and before doing silly stuff... sigh* LoL.

Join the club

 

[mhardy6647]

The question is why is the McIntosh emitting so much. Maybe it's because there's no load?

This is an interesting point.
A direct-coupled solid state amp ought to be as happy as a clam* with the outputs open circuited, but this amp certainly wasn't designed to operate that way. Mac will know the answer to this (begged) question and will provide it, I'm sure, if asked!
That said, if (!!!) the OP had some noninductive 8 ohm power resistors (dummy loads) to put across the (all) of the amp's outputs, it would answer that question a bit more scienificially than just randomly hooking up loudspeakers to various channels.
Interestingly, since we're talking about zero signal tests, the resistors wouldn't even have to be high-power resistors.

I guess, given the price and presumed sophistication of this amplifier, it would be prudent to ask Mac before just doin' it!
__________
* at low tide.

 

[Doodski]

Join the club

Yeah, I'm re-evaluating my approach for the future so I don't get stuck in a bonehead loop again like I was. Adjusting my operational flow chart per say. I should trust my peeps here at ASR when in doubt. I really distrusted the graph (It still has wonky lines I think.), the frequency analysis and the apparent fundamental frequency of 40 Hz. Like wow 40 Hz. First order of re-evaluation was to hop into bed hours ago and get some shut-eye. That made a big difference.

 

[Golf]

Again, I would try to make dead sure, that the problem is not the result of some room/house/mains related peculiarities.

I mean, nothing could be more frustrating than going through all the nasty and lengthy efforts combined to making McIntosh replacing the device – only to find out that the newly delivered amp shows the same behaviour as the old one eventually ...

 

[DonH56]

Wow ... Audition indeed finds a nice 120-Hz-pattern. But that seems to be based on 180 Hz as its starting point somehow:

View attachment 357906

The strongest spike I see is at 120 Hz in that plot?

 

[mhardy6647]

Again, I would try to make dead sure, that the problem is not the result of some room/house/mains related peculiarities.

I mean, nothing could be more frustrating than going through all the nasty and lengthy efforts combined to making McIntosh replacing the device – only to find out that the newly delivered amp shows the same behaviour as the old one eventually ...

That's the beauty of asking Mac!
They've been around since, you know, 1795 -- OK, since ca. 1949 -- this ain't their first rodeo!
They know the amp's design, performance, and capabilities. Further, they'll know its limits and what it does at or near those limits. They'll also know what if any circumstances might be 'triggers' for it -- e.g., how does it react to dirty power? Dirty power and no load on the outputs?
They'll also be able to suggest the best places to look in terms of troubleshooting and may even be able to suggest simple tests for a non-expert to do.
So -- yeah. I concur.



EDIT: Yay! I was right. 1949.

McIntosh Laboratory, Inc. | LinkedIn

McIntosh Laboratory, Inc. | 8,143 followers on LinkedIn. Defining the boundaries of audio excellence and luxury sound since 1949. Handcrafted in the USA. | Founded in 1949, McIntosh Laboratory, Inc. is known for offering distinguished quality audio products, superior customer service and the...

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[OldHvyMec]

The fault is repeatable in that it can be recreated anytime and the same fault occurs when moving a speaker near the McIntosh amp that is not connected to any speaker with wire.

Thanks, it was difficult for me to follow. So moving the speakers away from the amp lowered the floor noise (noise period)? I've owned Mcintosh for many
years and NEVER had a proximity issue. Rats nest of cable yes but proximity to a speaker? I don't have a lot of experience with B&W. I've had a lot more
sensitive speakers that's for sure and used SS Macs, never and I mean NEVER had noise issues, valves or SS.

If anything gets noisy I check connections and pencil test just in case. Tap the valves with a pencil. Other than that they go to the shop. 51 years and at
least 50 pieces still here. I sold all but one SS piece of Mac, the rest are vintage valve, BUT quiet as a mouse. I've use 106 sensitivity and 103 with
Jensen Imperials, still dead Quiet. The valve amps are next to the Cabinets when they are set up. MC240 in Mono for a little over 100 watts at 16 ohms.
No noise. Something is broken. Tongue in cheek.

I still say run a 120VAC extension cord from a neighbors house or drag it over to someone's house and check. Turn the mains OFF and check.

One SS Mac in 51 years for me and I bought it knowing one MB was noisy. It was the protection circuit if I remember correctly.

Thanks Dooski.

 

[Golf]

The strongest spike I see is at 120 Hz in that plot?

That’s very correct. While a lot of 60 / 120 Hz »multiples« can be seen right of it.

 

[DonH56]

Old article on "linear"" power supplies: https://www.audiosciencereview.com/forum/index.php?threads/power-supply-101-linear-supply.45884/

(I'd forgotten about this one.)