Slight humming noise coming from Mark Levinson 331

A ground lifter plug will probably take care of that. They are available in any decent hardware or electrical store.

Its most likely transformer hum which is a mechanical/vibrational thing. Sometimes it can be "cured" by tightening the transformer hold downs. Your dealer should be able to help you out. AKAIK, its not going to make it go up in flames.

Are you using XLR or RCA?

Transparent Ultra XLR's

Might want to check the connectors and make sure they are tight (inside and out). A buddy of mine has a 334 and he was getting some hum on his rca's and it ended up being a loose connection.
He also had a ML 38 preamp that hummed. He sold it with the hum so not sure what of the outcome? I have owned several ML amps with no problems.

Goodluck.

sam

The noise you are hearing is the transformer buzzing. You may want to check the power at the wall outlet with a volt meter...if possible. If it is 110-120v you are good...even 125v is ok, but the transfoemr will start to become noisey. I think around 130v the amp will shut down. Pay attention to the noise, it will probably change at different times of the day depending on the load on the main grid for the area.

Thanks for the information! What are my options if my voltage is irregular or over 130 volts?

Hey again, If the voltage is nearing 130v you need to contact your electric company ASAP. Once they come out to check the problem and see that it is high, they'll make the necessary adjustments at the main grid. Unfortunately, if the power is on the high side but still in range (+/- 10%) there maybe nothing they or you can do. The only thing then would be to get a good voltage stabilizer...of course it would need to be able to meet the demands of your current hungry Levinson. It's frustrating, I know, I'm living it. If you are only able to hear the buzz by puttig your ear up to the amp, you are fine. If it is to the point where you walk in the room and can make it out...there are some serious issues. Only other thing you can try is just what the other post says...check the bolt/nut that holds down the transformer. That's about it. FYI, my incoming power is 127v, if I put my ear up to my Levinson no.333 I hear a slight buzz. Before the Elect. CO. corrected the problem the power was 131v and boy was the amp loud!!

One more thing...All of the other amps I was using Krell, Parasound/Halo, Rotel, Sunfire...at 127v, they all buzzed! it's not just the Levinson.

In my equipment ML 331 is very nice and never lsten noise o humming!
Is better that somebody checking his power line at home!

hi Rick, i know it has been over a decade since you had that humming noise in your Mark Levinson 331.  i got the same thing in my 332 amp.  did you ever figure out what the cause of that hum was?

eelnad

The ML 300 series were plagued with poor OEM power caps so my guess is if you’re hearing a hum it’s the caps. Surprised if it’s the caps that you made it this long without having to recap. The bad news is if it needs recapped good luck getting it done through HK/ML but you should be able to find an independent shop to do it. Unfortunately it will not be cheap but you have a great amp and you’ll never replace it for the 1K or so it might run you to get it fixed. 
First step is you might have a ground loop so go to a hardware store and buy a cheater plug if you don’t have one to float the ground. Secondly make sure all your interconnects are away from power cables. If neither of these work take it to a tech to have it checked out. Again you have a great amp and definitely worth fixing if that’s what it needs. Good luck.