McIntosh Transformer causing noise in speakers while disconnected.

[ClassG33]

Update @Doodski @mhardy6647 @Zapper

I said originally the amp is silent. But if I press my ear literally up against the Transformer chassis (L) and power chassi (R), I hear it making this same noise on the inside. I cannot hear it unless my ear is suctioned onto it tho, so no audible SPL is coming out of the amp itself.

Still, the noise transmitting to the speakers is relative to the proximity of the Transformer chassis (L). Like I said, It is much more quiet when I switch sides, yet still audible (picture). Does that mean anything?

also, included the fact that nothing else is plugged into wall with stock power cable or interconnected, as this has been asked several times. I value power cables and Surge Protectors but If McIntosh says to do this with theirs, I believe them.

 

[mhardy6647]

... and just for (as I like to say) shoots and googles -- 150 Hz

EDIT: Same scale as the earlier post, finally I am a ready, fire, aim kinda guy, unfortunately!

 

[mhardy6647]

Update @Doodski @mhardy6647 @Zapper

I said originally the amp is silent. But if I press my ear literally up against the Transformer chassis (L) and power chassi (R), I hear it making this same noise on the inside. I cannot hear it unless my ear is suctioned onto it tho, so no audible SPL is coming out of the amp itself. Does that mean anything?

That's mechanical noise from the transformer (most likely) from the AC mains power -- the root cause is the same in the sense that it's an effect of the AC power entering the amp and doing various things, but it's more like a side effect with respect to the induced signal in your center channel loudspeaker.

 

[ClassG33]

That's mechanical noise from the transformer (most likely) from the AC mains power -- the root cause is the same in the sense that it's an effect of the AC power entering the amp and doing various things, but it's more like a side effect with respect to the induced signal in your center channel loudspeaker.

Figured it was expected, but making sure all variables are noted here since you're all being amazing helping me figure this out.

 

[mhardy6647]

Figured it was expected, but making sure all variables are noted here since you're all being amazing helping me figure this out.

It's a really interesting phenomenon.

 

[Doodski]

@ClassG33 here is a schematic of the AC to DC power supply basic type found in your McIntosh.
The orange square with D1, D2, D3 and D4 is the bridge.
Then red squares are the smoothing capacitors of the power supply.
The other orange squares are the positive and negative voltage output going to the audio amplification unity gain stage where the current amplification for your speakers occurs.

The electromagnetic energy inducted into your speakers comes from before the bridge on the transformer side
That is why you can hear the transformer when you put your ear to it.

 

[ClassG33]

@ClassG33 here is a schematic of the AC to DC power supply basic type found in your McIntosh.
The orange square with D1, D2, D3 and D4 is the bridge.
Then red squares are the smoothing capacitors of the power supply.
The other orange squares are the positive and negative voltage output going to the audio amplification unity gain stage where the current amplification for your speakers occurs.

The electromagnetic energy inducted into your speakers comes from before the bridge on the transformer side
That is why you can hear the transformer when you put your ear to it.
View attachment 357789

This is great knowledge, i love this!! Thank you for sharing your knowledge.

So all things considered now... is it unanimous that this is a defective amplifier and needs to be exchanged?

 

[Doodski]

So all things considered now... is it unanimous that this is a defective amplifier and needs to be exchanged?

It should not do what it is doing. There is the possibility that due to the high power output design of this unit, the immense toroidal rating/size and high toroidal secondary windings output voltage and current that another unit might have the same issue. You can only try to see if a replacement unit fixes the issue. I have not seen an amplifier induce noise into speakers when not connected by wires. This is a totally new thing for me to see.

 

[mhardy6647]

Sort of on topic
A little story from my youth.
I grew up in a home with some pretty good hifi of the DIY kind, assembled by my father who had been an AM and FM radio broadcast engineer (First Class FCC license holder) in the 1950s.

At one point in my childhood, the hifi consisted of a pair of EICO HF-12 integrated amplifiers and a pair of Electrovoice Wolverine LS-12 "full-range" 12
inch twincone drivers in bass reflex cabinets. My father had the amps, tuner, and record player in the basement and the speakers upstairs, so the speaker cabling was fairly long. The LS-12 drivers are quite sensitive (probably upper 90s in terms of dB/watt at 1 meter).
We were very surprised one day to hear, very faintly, a radio station playing through one of the two speakers! Nothing was turned on. The radio station was WFBR-AM in Baltimore. Their transmitter and antenna array in those days was not too far from our house (about 2 miles as the crow flies, in the so-called "Middle Branch" of the Patapsco River). My father's theory was that the long cable plus voice coil was acting as the antenna and resonant circuit, and (perhaps) a 'defect' in the voice coil winding was acting as the detctor (i.e., extracting the amplitude modulated signal from the carrier at (then) 1300 kHz. The driver's high sensitivity transduced the detected signal to produce audible program. Sort of an accidental implementation of a so-called "foxhole radio" receiver.

Foxhole radio - Wikipedia

en.wikipedia.org

As it happens -- I still have one of those two LS-12s -- and a few more besides Not the enclosures, though.


In the present case, though, the loudspeaker seems to be responding directly to the "carrier" frequency (or a harmonic thereof)... I guess...

 

[Philbo King]

If you have an Android phone, try this app to measure the magnetic field around the outside of the amp:
Keuwlsoft AC Magnetic Field Meter

Try holding the phone at various angles relative to the amp. Share a screenshot of the highest reading you can get.

 

[Doodski]

We were very surprised one day to hear, very faintly, a radio station playing through one of the two speakers!

I experienced a similar issue. I was operating the turntable, the sound was up fairly loud when I heard radio communications from a pilot overhead in a small aircraft. It was clear as could be and I heard every word easily at a loud volume. I replaced the amp and turntable toot suite and never had the issue again.

 

[mhardy6647]

I experienced a similar issue. I was operating the turntable, the sound was up fairly loud when I heard radio communications from a pilot overhead in a small aircraft. It was clear as could be and I heard every word easily at a loud volume. I replaced the amp and turntable toot suite and never had the issue again.

I'll bet it was the coils in the cartridge picking up the signal Lots of gain downstream of them.

 

[Doodski]

I'll bet it was the coils in the cartridge picking up the signal Lots of gain downstream of them.

It was awesome I thought... very cool.

 

[mhardy6647]

Coils are magical things.
Every transformer contains at least two of them, inductively coupled.
As shown in the power supply schematic @Doodski posted!

The 60 Hz mechanical hum is not "the same as" the 60 Hz electromagnetic field, but they both arise from the same thing (the 60 Hz AC mains frequency).

EDIT: And actually a resonant circuit is the most magical thing of all!

 

[ClassG33]

If you have an Android phone, try this app to measure the magnetic field around the outside of the amp:
Keuwlsoft AC Magnetic Field Meter

Try holding the phone at various angles relative to the amp. Share a screenshot of the highest reading you can get.

On it.

 

[Doodski]

The 60 Hz mechanical hum is not "the same as" the 60 Hz electromagnetic field, but they both arise from the same thing (the 60 Hz AC mains frequency).

There is so much stuff going on in the power supply and the power transfer from the mains transformer on the pole to the audio amp circuitry that I hit the main points and skipped some stuff in effort to make this as painless as possible in understanding the basics to the degree that you peeps in this thread can absorb and figure it out. It is not exact and inclusive of every single detail but it's near close. I made some grammatical errors along the way even though I proof read several times each post.

 

[mhardy6647]

I edit a lot. I try to own up when I do.
Ready, Fire, Aim really is one of my mottos.
Of course -- so is Strive for mediocrity -- because for some of us, it's a stretch goal.

 

[ClassG33]

On it.

Note: it spikes when i press to take screenshot. The last 2 are the most accurate without movement changing the readings.

In front of center speaker at center driver:

To the right of Power Supply chassis right side of amp, between amp and speaker:

On top of amp, above Transformer side.

To the left of the amp, Transformer side:

 

[Doodski]

I edit a lot. I try to own up when I do.
Ready, Fire, Aim really is one of my mottos.
Of course -- so is Strive for mediocrity -- because for some of us, it's a stretch goal.

I find the technicality of this textual communication to lend me very strong spoken word organizational skills. When I speak now I always minimizing my words, skipping all those extra words that are not required. I also use the proper words and of course substitute generalizations the word, "Stuff." Sometimes peeps I speak with really don't need all the details and we all know what the stuff is. LoL... I really need to get the <;> function use understood. I never seem to be able to use properly and I fudge it always.

 

[mhardy6647]

Apples to apples - I ripped the whole second video with Audacity. In other words the time axis is true to the original video.