1. Ground lift or isolate the power of the unit to a single CLEAN power source
2. Double check cables (I work with a lot of rental samplers that have worn 1/4 connections & replugging sometimes helps)
3. Try an impedence transformer (@$30 each) or a passive DI box (these almost always fix the problem)
4. Move the sampler & it's connections as far away from any other live cables (that might be sending interference to the sampler & its cables)
5. Try useing a filter/eq and notch the buzz out (although it will probably change the sound)

(snipped from the DUC re: Gary Stadler)

60 cycle hum is usually caused (in a home studio) by the ground loops created when you plug two or more audio devices that have a ground pin on their power plug- into a plug strip. All of the ground pins are thus connected together, and since all of the audio grounds of those units are also connected together, it creates a gigantic mess of ground loops that are sometimes impossible to eliminate.

Often people cut the ground pins of their power cords off...sometimes it works but it's more than likely to make things worse and unsafe. There are usually little capacitors inside a typical unit's internal line filter hooking power line to chassis...when you lift a ground pin these can -and do- cause shock hazards, and a different kind of hum that is often worse than the origional!

I'm the right guy for the solution...but at the wrong time....I used to make a thing called "Humbuster" that was essentially a 2U rack box with 10 power isolation transformers inside, each of 10 110vac plugs on the rear had no electrical connection of any kind, including ground, to any other plug on the rear...it was so simple- just plug your gear in to the box and ground loops instantly and safely gone! But the world evidently had a hard time spending $500 bucks on magic that instantly cleaned up studio hum when the same $500 bucks could buy a new synth module or plugin, so we eventually quit making them- it was too much of a fight to make even a small profit....the 200 or so customers we did have were totally amazed at how simple it was and how well it worked...
Balanced power from Equitech is a different solution that works pretty well, but it raises a LOT of safety issues, and it's a hassle to install correctly.

Email me privately... nightsongs@home.com if you can't get your hum fixed...perhaps I can make one last humbuster for you if you're interested...

(snipped from the DUC re: Gary Stadler)

I have a number of ribbon mics with low gain. It seems no matter which mic pre I use, I get hmm. When I bring the gain to where I need it, usually the last 10 db or so of the (60db)pre I hear hum in the signal. This is still the case with every ribbon mic I have, beyers, coles, b+o except for the beyer m160 which has a hotter signal. What do you recommend for dealing with this?

Henry Shapiro
Big Shot Recording

Henry,
Tell us some more about your gear. Which pres do you have? What kind of wiring / how is the mic connected to the pre? Do you have a lot of dimmers or flourescent lighting? Computers/monitors? Is the electical system properly balanced?

There are so many things that can cause hum, tracking then down will require a lot more background info.