Amplifier hum - normal?

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.

Kijanki,
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:
http://www.soundstage.com/maxdb/maxdb071998.htm
.

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.

There's also the Humbuster III from PS Audio. The DIY solution costs much less though.

http://diyparadise.com/dablok.html
.

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:
http://img.villagephotos.com/p/2003-5/191557/DC%20Blocking%20Circuit.jpg

Enclosure and two types of 1/2" cable connector/strain relief:
http://img.villagephotos.com/p/2003-5/191557/J_BOX.jpg

.

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.

If you are referring to the OP, I built him a DC blocker that cured his hum problem.

http://img.villagephotos.com/p/2003-5/191557/DC_BLOCKER_02.jpg