[floresjc]

I have a double 440 and a double 240/3. They make a low level humming noise from the unit themselves. I would judge the 240/3 as being louder, although both are pretty quiet (ie get lost in the background noise of the house). The 240/3 is slightly audible from 5-6ft away. Is this cause for concern or out of the ordinary? I figured for the most part the amps should be dead silent, unless they have a fan or something in them.

Update: The 440 is definitely a lot quieter when on, its hard to hear even when putting my ear right next to it. The 240/3 you can tell if its on from several feet away pretty easily in a quiet environment. Both have a buzzing "transient" as you flip the power switch on which settles into their hum. Is this normal?

[oneinthepipe]

The 240/3 is slightly audible from 5-6ft away.

That isn't normal, in my experience.  Call Frank.

[srb]

Transformer humming is often caused by a DC voltage component present on the AC line.  Are the units plugged into any type of power conditioner or filter?
 
Steve

[Wayner]

These amps do not have the usual core and coil type transformer, usually associated with buzzing, but rather a toroidal type transformer. There are no other ill effects, but the transformer may have become a little loose and that is what is causing the vibration hum, sympathetic to the 60 cycle and it's harmonic cousins.

Wayner

[floresjc]

No power conditioning of any sort being used. The 440 has the buzzzzz at power up then dies to nothing within like a second or so. The 240/3 settles out into a nice hum, kinda sounds like a refrigerator running although not nearly as loud. Its hard to describe, its quiet enough that any source material wouldn't be affected, but its loud enough that in a quiet environment you can tell its on, which shouldn't be the case in my opinion. I sent an email off to Frank and hopefully he can chime in. I might try and unplug the 240 and bring it upstairs to see if its the environment and if its as quiet as the 440 plugged into the same spot.

[Wayner]

It could be something as simple as a wire sympathetic to the transformer. Sometimes, the location of the amp may naturally amplify low level noise, such as proximity to the floor, or rear wall or even worse, a corner or a combination or all three. Sometimes an enclosed cabinet can start to act like a resonant chamber, amplifying the low freq.

Wayner

[charmerci]

The 440 has the buzzzzz at power up then dies to nothing within like a second or so. The 240/3 settles out into a nice hum, kinda sounds like a refrigerator running although not nearly as loud.

Yeah, I know that 440 buzz. It happens with my AVA Mos-Fet D in an old Dynaco chassis. It too also has the 240/3 vibration/buzz/hum. I did send it to Frank (a number of years ago) to have it checked out and he said it was fine without any comment about the noise.

My guess is that you just have to live with it.

[floresjc]

Maybe the location is not so great. Its in an open cabinet, but the bottom shelf towards a corner of the room. I'll move it around and see if that helps too. It only bugs me because I know its there, it doesn't seem to be impacting material when I play it, because overall it is low level.

[avahifi]

Often the cause of audible hum from a unit with a toroid power transformer is low level DC floating on your AC power line.  This can be caused by any appliance (hair dryer, etc.) that reduces AC line input with diodes internally.  I saw a well done scientific article on this that explains that even a tiny fraction of a volt can upset toroids.  If anyone can find that article, they are welcome to post it here.

My suggestion is to try the amplifier on different AC circuits in your home and see if the hum goes away on some circuits, if so then search for the culprit.

Regards,

Frank Van Alstine

[turkey]

reduces AC line input with diodes internally.  I saw a well done scientific article on this that explains that even a tiny fraction of a volt can upset toroids.  If anyone can find that article, they are welcome to post it here.

This one? http://sound.westhost.com/articles/xfmr-dc.htm

[avahifi]

Correct, this is the article about DC on AC power lines making transformers unhappy.  Recommend reading.

Would be a nice thing to design into expensive power cords - blocking DC there would be of real value.

Regards,

Frank Van Alstine

[floresjc]

Well I figured out that it is indeed not the amps fault. I've flipped it on an off a few dozen times the past day or so and it has varying degrees of hum. It goes away nearly completely if I run it through the Panamax power conditioner I have, and I also figured out that my plasma has a hum to it which sounds exactly the same as the amp. So the amp itself is alot quieter from farther away than I thought, it was a combination of hums that I was hearing which was mostly the plasma.

In the new house I'm setting up dedicated circuits for the amps, hopefully that will help as they are in a pretty noisy environment right now. May also have to get a filter/conditioner of some sort if those lines are contaminated as well.