Hum & Buzz - Audio Nightmares of Today...

#2 GROUNDING ISSUES AND HUM LOOPS: There is Often Hum in the System, and it is hard to identify and fix.

 by Frank White with Anthony Grimani

The next rendition we worked for Tony, enjoy...

This comes from our list of the top 50 recurring problems in home theater systems - gathered over the last 25 years from more than 1,000 high-performance installation projects.

Most have been there: The project has gone just too dang smoothly. The gear arrived on time, the construction schedule was maintained - karma, chi, and wha are in balance.

Your relationship with the interior designer actually grew and both teams are on the same page. Once you have loaded in the technology, it's time to light up the entertainment system: the projector fires up, the screen lowers, and the audio arrives.

That's when you discover that the light at the end of the tunnel is really a blitzing locomotive with your org's name firmly tattooed right on the front. You have a bit more audio than you anticipated. Hum and buzz, the dreaded bane of the tech world, has just appeared like a terminal rash.

Guess one way to look at it is that you scored some, uh, free audio? Maybe not so much.

Situational frame: You have dozens of pieces of expensive gear all plugged into multiple circuits. Everything except the diffusers will be affecting and managing electrical current. On one hand, you have the "dumb" lighting fixtures. On the other end of the complexity shelf, you have the content engine, the control system, and a hybrid communication arena firing commands, content, and status codes all over the neighborhood - even the UPS module is a constant toxic cloud of RF communication. Any and all components could come into play in the hum and buzz war.

Where, dear and gentle reader, does one start?

Don't just stand there asking, "Whisky Tango Foxtrot?" It is now time to earn your stripes.

Each component is consuming and/or transforming energy into its designed state. The different power supply types, grounding, and safety circuit topologies are a recipe for frustration, inappropriate aging, finger pointing, and all-around angst. 

Many technology contractors have very vivid and dark nightmares about this one scenario - hopefully not recurring on every project. You can spend hours troubleshooting, "plug-festing", and even pulling out your precious little hair.

But the hum remains.

SOLUTION Understand how line power works. Any time you are using multiple circuit loads, the possibilities for hum rise logarithmically. When you have different grounding paths, as you do in multi-circuit systems, each circuit will have a different ground potential. Although it can be quite small, it is still a fact.

The definition of "difference in potential"? That, my friend, is voltage. In this case, catastrophic. Figuring out which component - or which combination of components and their power supplies - are at odds then becomes worse than a Three-card Monte scheme, with you on the wrong side of the table.

Or, you could save yourself a lot of frustration and delays by designing systems that are all digital - with proper ground isolation from product to product, proper ground topologies, and proper isolation transformer power supply conditioning. You should also have a supply of various Jensen brand signal isolation transformers -- take a look at their website for choices and education, and call them for more help if needed; they are very friendly and smart about all this hum (and buzz type) stuff!

While on the web, check out Anthony's new offerings at Grimani Systems.

You can get ahold of me at [email protected]