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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.
djembeplay
gbart
290 posts
 
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.
sidssp
1,077 posts
 
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.
djembeplay OP
178 posts
 
Hmm... I'm not sure what would constitute excessive or normal. I have sensative ears... lol, but I'm sure we all do here.

Idk.
kijanki's avatar
kijanki
4,394 posts
 
"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.
gbart
290 posts
 
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
.
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