Amplifier hum - normal?

Is it normal for amps to emit a slight humming noise from the transformer when turned on?

I never noticed it in my old integrated that I lived with for over 10 years, but that was lower power. Now I've gone from 50wpc to 120wpc... don't know if that makes a difference here though.

I mean, it's not nearly enough to bother me or even really be audible past 3 feet away... but I am curious if this is typical for amplifiers to do this.
Some do and some don't.

From my experience, tranformer hum has no correlation to an amp's power rating.

It has more to do with the quality of transformer and amp design.
I have found that higher power amps tend to have a little hum to them. Some more then others. If you can only here it from 1-2 feet in a silent room, that it pretty normal.
I have a Yamaha M-40... did they use quality transformers?

It is pretty quiet... i would say you could barely hear it from 3 feet away from the chassis top in a silent room.
I have owned several SS amps.

Bryston 4B SST - no hum whatsoever
Bryston 14B SST - no hum whatsoever
McCormack DNA-2 - no hum whatsoever
Odyssey Stratos Mono Extreme - no hum whatsoever
Belles 350A Reference - no hum whatsoever
Belles 150A Reference - hummed like a $10 hooker
Pass Labs XA-60.5 - no hum whatsoever

My history with SS amps suggests that no hum is more common than hum.
I too have owned a good number of high powered solid state amps and never had any hum issues. I have had hum problems with large toroid isolation transformers. A lot of modern amps have toroids, which are more prone to humming and buzzing as a result of DC on the power line. I would look to exclude this as a possible source of mechanical hum.
All transformers will hum a little but only poorly constructed ones will generate excessive hums. I would consider that a defect if you can hear it more than a few inches away, especially in a modern high-end amp. The propose of a high-end amp is play music in a quiet room. It shouldn't hum at all.
Hmm... I'm not sure what would constitute excessive or normal. I have sensative ears... lol, but I'm sure we all do here.

"A lot of modern amps have toroids, which are more prone to humming and buzzing as a result of DC on the power line."

As far as I know Toroid is very quiet compare to non-toroidal transformer. In addition is more efficient because of low stray magnetic field (one tenth of traditional transformer) and higher power rating for the size because of higher flux densities (up to 18000 Gaus vs 14000 Gaus in non-toroidal transformer).

The only disadvantage of toroidal transformers that I know of is cost of winding.
It seems like you've rehashed what you've read on Wikipedia without getting a proper understanding of the facts. Yes, toroids are generally mechanically quieter than E-I types, EXCEPT when subjected to DC.

The core of a toroidal transformer saturates more easily than that of an E-I type transformer. Because of this, toroids tend to have higher inrush current. DC offset on the power line will also cause magnetic saturation of the core of a toroid more readily than in an E-I type transformer. As the toroid transformer attempts to recover from the saturation, this causes a buzzing sound.

Manufacturers like Equi=Tech and Plitron employ manufacturing techniques in their "Q" type and NBT type transformers respectively that help make them less susceptible to this core saturation.

See here:
So this humm isn't something that indicates a poor-quality transformer or a malfunction?

A friend used to have an older Crown amp and he said it used to buzz much louder than this Yamaha.

Also, I wanted to add... whatever I have my volume set at makes no difference what-so-ever. With my amp gain all the way down, I still hear the same buzz.

Thank you - that was very informative.
Only black from my Yamaha MX1000 U. It's both very high wattage and vintage.
Really? Hmm... Your not referring to noise coming through your speakers, right?
Djembeplay, hum can come from things like loose transformer laminations, loose mounting bolts, other internal issue, or DC. Trying to do an accurate diagnosis on the Internet is difficult and the best that can be done is to offer suggestions.

You need to go through a process of elimination, IMO the first and least intrusive step being to rule out DC. Try disconnecting devices/shutting off breakers to see if a connected device is the cause. You could also try the amp at a friend's house to see if the hum persists or goes away.

If you are still getting the hum, the next step would be to remove the amp's top cover and check for loose mounting. In the end it could just be that the transformer is noisy. If DC is the cause, there are solutions that include eithar a manufactured or DIY DC blocker.
Channel Islands Audio makes a CD blocker called the XDC-2. You could give it a try. It's available with a 30 day trial period (10% restocking fee applies for returns).

In my system, the XDC-2 knocked down the transformer hum, but it did not eliminate it completely.

There's also the Humbuster III from PS Audio. The DIY solution costs much less though.
Hmm... DIY you say... how would one go about such a project?
Install the DC blocking circuit in a metal enclosure with a 120V 15A single or duplex receptacle. Insert the blocker between the incoming HOT line and HOT terminal of the receptacle.

Its probably easiest to install everything in a 4" x 2 1/8" or deeper steel electrical junction box and use a cover plate with holes for a single or duplex receptacle. Alternatives are a metal power strip enclosure or aluminum project box.

You can use a 3-wire grounded 14 gauge or 12 gauge power cord for the input and be sure to bond the incoming ground wire to both the metal box and ground terminal of the receptacle. Also use an appropriate strain relief at the point where the cord goes into the box.

The caps and diodes can be obtained from Radio Shack, Parts Express, Mouser, etc. Radio Shack does not seem to have 3,300uf caps but they have 4,700uf 35V which will also work.

See this circuit:

Enclosure and two types of 1/2" cable connector/strain relief:

Hmm... I think it's a bit over my head. I've never made a circuit... but, I suppose this may be a good place to start.
Do you have a friend or relative with good basic electrical knowledge to whom you can turn for help ? If you are unsure of your skills, then don't attempt this. Also, the cans of the capacitors are going to be at line potential. They have plastic shrink labeling around them but there is still some bare metal exposed. You need to exercise care that these don't come into contact with anything else. Observe polarity of the caps and diodes. The caps usually have a (-) marking on the side with the negative lead to indicate polarity. The diodes have a band on one side to indicate the cathode (negative) side.
See this circuit:

The only 1000V diode is 1N4007. 1N4001 is only 50V
I do have a relative that is good with soldering and circuits. I'll see if he's up for a project - could be fun.
The PS Audio Humbuster III worked pretty well for me. Give it a try, most places carry a 30 day money back guarantee. Not much risk.
I'm with Studio68.

Why not try the PS Audio Humbuster or the Channel Islands XCD-2, whichever is available with a home trial.

At least that way you'll determine if DC is the cause of the hum before you go messing around building a DIY DC blocker that may be unnecessary.
Resurrecting this discussion, if the hum has increased over time (and increased consistently over that period, not ebb and flow), would that pretty much rule out a DC source i.e. more so a fault of the transformer, the fault becoming worse with time?
If you are referring to the OP, I built him a DC blocker that cured his hum problem.