From the MC8207 owner manual Power Supply Circuits
To compliment the design of the MC8207, there is a high current power supply for the five power amplifier channels. Refer to figure 21. The very large Power Transfomer, has toroidal windings on a toroidal core and can supply over 35 amps of continuous current. Refer to figure 22 (golf ball is for size comparsion). It is enclosed in the legendary McIntosh Potted Enclosures and weighs over 12kg. The super size main filter capacitors can store over 340 Joules of energy for the seven amplifier channels, necessary for the wide dynamic range that “Digital Audio” demands. The power amplifier draws high current from the AC power line. Therefore, it is important that they plug directly into the wall outlet.
See page 15 http://stereobarn.com/wp-content/uploads/mcintosh-mc8207-amplifier-owners-manual.pdfWhere’s the second transformer? Am I missing something? The very large Power Transfomer, has toroidal windings on a toroidal core and can supply over 35 amps of continuous current. 120V X 35 amps = 4200VA. Just a guess the transformer is rated at 5Kva. |
Simple solution. Take the second defective 8207 back to the dealer and get your money back and if he is the one that sold you the Niagara get your money back for it too. Then find a HT amp from another reputable company with customer service and buy it. There are plenty of multi-channel amps on the market even if they don't have blue meters that will work in your situation. If only one of multiple transformers on the same chassis makes noise then the problem is not your house. Don't waste any more time or money trying to fix McIntosh's problems as they are not the McIntosh of old. |
@jea48
With my amp only one is buzzing, the left one, so lets say I do have dc on my ac line why would only one buzz? IMHO I think that the one that buzz is a bad one comparing to the right one which is a good one. It would be the only explanation.
So what I did was, I turned off every switch in the house except the on the amp is plugged in and yes the buzzing sound got quieter but was still present. But having an expensive amp that has much better transformer than a cheap amp this little interference when all breakers are on should do nothing to it.
I bet you that every house has the same problem when you have multiple things running in a house such as ac units, furnaces, washers and dryers etc, you can't tell me that there is going to be no interference at all, but this expensive amps should take care of that problem. - I could be wrong. |
He already did that. He took the amp to a friends house and it still buzzed.
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Not all transformers will respond the same. Try taking the amp to another building and see what happens.
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@ tomiiv30 As for DC on the AC mains. Nelson Pass
If you are experiencing mechanical hum from your
transformer, it is often caused by the presence of
DC on the line. Usually this comes from some appliance
using current asymmetrically, such as a lamp dimmer.
The hum comes usually from toroidal transformers, which
saturate easily with DC, and when they recover, they
draw an extra pulse of current, causing the noise.
You can put a pair of back-to-back electrolytics in series
with the AC power line to block this, and it works fine.
Makes sure the current rating of the electrolytics is
high enough, and the they are joined at a like polarity,
such as + to +. https://www.diyaudio.com/forums/solid-state/2080-dc-filter.html Re: Not trying to start a flame but.... "If your not comfortable with a meter get an electrician or tech that knows his way around test equipment. " If you read the comments in the AA archives, you would have seen the ones from real engineers (Jon Ricsh, John Curl, etc)who have measured this. They report that most hand held DVMs cannot measure this (John Curl tried three different Fluke models with mixed results). If you really want to try and measure the DC off-set on your AC line with a cheap hand-held DVM, try the following: Put a 100K resistor in series with a 100µF cap (this is called an integrator). This now goes in parallel with the AC line. Measure the DC voltage across the cap. Even a few tens of mV DC off-set can make a toroid buzz, especially low priced ones. The image here is a PA Audio DC blocker. Note the two series connected bridges, this gives four forward diode drops vs the two of the Bryston circuit. Note also that the caps in parallel with the diodes are very small, just for RF suppression. The original LC Audio filter was similar to this PA Audio one as well, only they used three forward diode drops, and only small RF caps.
http://db.audioasylum.com/mhtml/m.html?forum=tweaks&n=140383&highlight=integrator+djk&r=...JMHO, if the mechanical buzzing on one of the transformers is caused by DC on the AC mains, then both transformers would be buzzing. . |
@erik_squires
But what makes one transformer to buzz but another not. Wouldn't you think that when you spend this kind of money for an amp to be quite even if there is a little DC offset in the AC line, plus there was another guy that said there is no such thing as DC in AC line, so which advice should I go for.
Even my electrician was confused as to what I was trying to fix, and when I told him how much money I paid for the amp he was laughing his arse off.
He was trying to make me happy and do whatever I asked him to do even though he did not wanna do anything because everything looked fine to begin with.
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You got a bit of bad advice.
Mechanical transformer hum comes from having DC on the AC line.
Isolated lines or ground do not help you.
First check your AC for DC. An electrician should do this.This can be caused by lights and dimmers elsewhere in the home, so you may diagnose this by shutting off everything but your amp.
Fixes include:
- Switching to other phase
- Using a balanced power conditioner.
Most power conditioners are not balanced so won’t help.
Best,
E
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@jea48
I am in the USA
I will talk to the electrician when he comes back from vacation to find out what exactly he did, I may say things that are misunderstood since I am no electrician by any means, but for what I know is that I have an isolated 20 amp outlet that has it's own grounding and that's pretty much all I know and I know that there is a copper poll in the ground by the outside electrical wiring. I can tell you more once I talk to him. |
@cleeds...…………………….
I received 3 private messages. There also were a few posts in answer to my post but they seemed like guesses.
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tomiiv30 OP11 posts01-02-2019 8:10pm
@stereo5
I just got an email from the salesman I bought it from and told me that he would talk to service dept. to see if they can check or have checked the one I returned. I would also be bringing this one to them as well and have them plug it in while I am there no matter how busy they are.
Check the serial numbers of the two units. My bet is they are close to one another. |
stereo53 members of the forum told me there was a bad batch of the potted transformers which was confirmed by McIntosh. That certainly wasn't publicly posted in the forum. Are you saying that AA users told you that privately?
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@ tomiiv30 Your profile list country as N/A. By chance do you live in the USA? I have McIntosh MC8207, the first unit I bought from an authorized dealer came with a loud buzzing coming from the left transformer, and was replaced with a new unit which came with even a louder buzzing. The buzzing can be heard from 8 feet away. Then I was told to have install new 20 amp outlet that has its own isolated grounding. That was done professionally by an electrician who installed two isolated 20 amp outlets, two 20 amp circuit breakers, two copper polls for grounding for each outlet, each outlet has its own neutral and power line. After all this done the buzzing sound was still there. Then I was told to have install new 20 amp outlet that has its own isolated grounding.
That was done professionally by an electrician who installed two isolated 20 amp outlets, two 20 amp circuit breakers, two copper polls for grounding for each outlet, each outlet has its own neutral and power line. After all this done the buzzing sound was still there. If you live in the USA the so called electrician is no electrician. Definitely not a qualified licensed electrician. No way in hell! two copper polls for grounding for each outlet, I assume you mean two earth driven ground rods. DANGEROUS and not electrical safety code compliant. Not NEC or any AHJ in the USA. IF the branch circuit wiring is Romex an isolated grounding type receptacle serves no purpose what so ever. Per NEC code the insulated equipment grounding conductor that connects to the isolated ground terminal on an IG receptacle shall terminate on the ground bar in the electrical panel the branch circuit is fed from. Exception: NEC allows the insulated IG equipment grounding conductor to pass through a sub panel and to be connected to the equipment ground bar in the main electrical service panel. NO isolated ground rods allowed for IG receptacles. |
3 members of the forum told me there was a bad batch of the potted transformers which was confirmed by McIntosh. Let the dealer know about that. Best of luck and let us know how you make out. |
@stereo5
I just got an email from the salesman I bought it from and told me that he would talk to service dept. to see if they can check or have checked the one I returned. I would also be bringing this one to them as well and have them plug it in while I am there no matter how busy they are.
And thank for posting in the other forum for me, I really appreciate that. I just don't want to spend another cent on trying to fix something that may not be fixable by me. |
I own a Mac MC152 power amp and a MA6600 200wpc integrated and both are dead quiet. I have never heard of that. I will ask over at Audio Aficianardo Mac forum and see if others may have a clue. I’ll report my findings back here. Did you or the dealer check to see if the transformer is bolted down tightly?
This is what I posted on Audio Aficionado:
McIntosh MC8207 Transformer buzzing
I am asking this for an Audiogon member who is having a hard time with this amp. He bought from a reputable authorized dealer and the left power transformer buzzes so loud he can hear it from his listening chair 10 feet away. He returned the unit for another amp and it has the same problem. He contacted McIntosh service on 3 different occasions. They first told him he needs dedicated lines so he had a licensed electrician do that, having 2 lines installed both with separate grounds, but no change. Then service told him to buy a power conditioner and he bought an Audioquest Niagra to the tune of 4 grand and still no change. The last time factory service told him he needs a DC Offset Blocker.
It seems to me they are taking stabs in the dark. He brought both amps to his friends house 10 miles away and the same problem, the left toroidal transformer buzzes. His house is new, only 5 years old with a 200 amp service. He is quite ticked to say the least. I feel bad for the guy and I am trying to help him out. Anyone??
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@stereo5
I returned the first unit to them and they had all this time to check it and tell me what the deal is, but so far I have heard nothing.I can return this one for a full refund that would not be a problem but I am trying to resolve this issue, and my question is why am i hearing the buzzing only from the left side and not the right, if I have a DC in my AC Line wouldn’t it both side be buzzing? |
Did you try either amps at the McIntosh authorized dealer? If it is ok there, then there is a problem with the power line. If it isn’t ok, then the unit is defective. At any rate, your dealer should be bending over backwards for you. If not, I would demand a full refund. |
@kalali
I did buy from reputable authorized McIntosh dealer and the dealer replaced the first unit with a second brand new unit which has a louder buzzing and it is coming from the same left side of the amp. I am suspecting that somehow McIntosh has built defective transformers since these two amps were bought within one month period, but this is only a guess. |
Emotiva CMX-2! Killed the buzz from my Classé CA-200. Now dead silent.
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I would have expected the buzzing sound to come from both transformers if it’s due to DC riding in your AC line. Secondly, I’d also find it unlikely if it happens after all your efforts and also in your friend’s home. I’d consider getting it replaced if you bought it from a reputable dealer instead of going down a rabbit hole trying to fix the symptoms. A power conditioner rarely if at all addresses a transformer mechanical buzzing. |
Audio by Van Alstine make a relatively inexpensive but excellently built model. They also have a generous return policy. If McIntosh can't or won't help, it would be worth trying (if only to eliminate the possibility). |
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I don't know much about McIntosh, but always thought they had a great reputation.
What you are describing isn't something that should be happening.
You have done everything correctly, and the issue persists, so it would seem the problem is equipment related.
The only other cause would be the power coming into your house.
Do you live in a rural area, or use your own power source?
Second, if you bought from a dealer, he/she should be by your side getting this rectified. Period.
I hate it when good people get the run around.
B |
