Hum has no place in an audio system. It’s often caused by improper grounding. When I worked at The Absolute Sound from around the mid-1980s through the mid-1990s, eliminating unwanted hum was a constant struggle. (Well, one of many constant struggles but I digress…)
Since the TAS systems were (mixed metaphor alert) audio magnifying glasses, such noise could be anywhere from annoying to maddening. And with editor in chief Harry Pearson in the listening chair I had to do everything I could to make sure it wasn’t present. Anything and everything…
A major cause of ground hum is a ground loop. This can occur when an audio system is connected to ground at more than one point, such as when the various components in a system have their AC power cords plugged into outlets in multiple locations. It can also happen because the components have their grounds connected via their audio interconnects; for example, the interconnects between a preamp and power amp.
So, when I would get ground hum, the first thing I would try to do was to break the ground loop. Sometimes I got lucky and could just happily plug everything in…preamps, phono stages, monoblock amps, turntables, CD players, at times electrostatic speakers all at once…and the system would be noise-free. Other times…hum hum hum, aarrgghh!
Here’s the disclaimer portion of the program: I am not a licensed electrician. I’m NOT recommending ANY of these procedures and will not be held responsible if you try any of them.
My standard first step for eliminating hum would be to use a “cheater plug,” one of those 3-prong to 2-prong adapters. Back in the day we thought nothing of it; today, as Wikipedia so eloquently states, “this practice has been condemned as disregarding electrical safety.” In fact, they’re illegal in Canada and other areas.
You’re supposed to use a cheater plug as an adapter for plugging three-prong AC plugs into old “grandfathered” two-prong outlets. You’re supposed to connect the grounding tab of the cheater to an electrical ground, such as the screw that connects the wall plate to the outlet. But I wanted to break ground loops! So, I never did that. In fact, sometimes I’d use multiple cheater plugs, since some audiophile sages had decreed that a system would sound its best if it was only grounded via one 3-prong AC cord, with all other cords floated.
Not only that, but received wisdom at the time was that you should try the cheater plug oriented both right side up and upside down to see which way sounded better.
I would start by taking a voltmeter and touching one probe to the chassis of a component, or a grounding post on, say, a preamp and sticking the other probe into the grounding hole of the wall outlet. I’d have to poke around to make contact with the metal in the hole. (Somehow, I never got shocked.) Then I’d note the AC volts reading on the meter. It would usually be close to either 120 or zero volts. If the latter, fine. If the former, flip the plug! Sometimes I’d have to go into plumbers-butt contortions to hold both probes and look at the meter.
I would then flip each plug for each component and listen to see if the sound improved. (Hours of agony but I had to maintain what we strived to create as the Best System on Earth.) Sometimes it did. So, the cheater plug would stay upside down.
I had a bunch of cheater plugs, including the now-discontinued type with a grounding wire rather than a metal tab for even more hazardous adventure. But, some of them had a bigger prong on one side to assure they’d be properly oriented when plugged in the “right” way. If I had to use them upside down I’d file the bigger prong down. Safety second!
Some audiophile power cords are big and heavy. And if you used a cheater plug with them, they’d tend to want to fall out of the outlet. As a result, before every listening session I’d check to see if the cords were loose. Yes, there was a time when I actually did this.Ground loop diagram. Courtesy of Wikimedia Commons/Chetvomo.
But sometimes even all of that didn’t work.
And I had to get the systems up and running for El Exigente. So, more rule breaking.
This usually involved taking lengths of wire and connecting them to the metal parts of the different audio components in a system, sometimes running them in what I pathetically hoped would be a “star” grounding configuration, where all the grounds in a system went to a central point (hence the “star” appellation), sometimes festively stringing wires between them in daisy chains. Or, running wires from the components to the ground screw or grounding hole on a wall outlet, usually by shoving one end of the wire into the hole. (Wish I had pictures!)
Sometimes I’d have to wedge the wires between, say, a top cover and a chassis. Fun when taking apart a $5,000 preamp. I can proudly boast that I resisted the temptation to scrape paint and anodizing off a component in order to make a good electrical connection. More than once, a faceplate would provide the best ground so I’d tape a wire to it. (I was careful to use only scotch tape, since I didn’t want to return a component to a manufacturer and have them wonder why it had tape marks on the faceplate. Unlike the time we returned a speaker with hand truck marks across the front, but that’s another story.)
Turntables could be especially problematic. Many times I had to ground the turntable to something other than the grounding screw on the preamp – you know, what you’re supposed to do. Sometimes I could eliminate the hum by not connecting a grounding wire, or connecting two wires to two different places. A few times I tried floating the entire system – in other words, not connecting anything to the third prongs in the wall outlets. This worked at times but even my younger and dumber former self would never leave a system like this.
It was all strictly trial and error – turn everything on and start poking around until the hum went away.
But there were a couple of times when I had to go from desperation to the Bizarro World. (Also known as Htrae, which is “Earth,” another term for “ground,” spelled backwards.)
One hot summer day I was trying all my tricks and nothing was working. I figured, screw it, maybe Harry won’t notice the hum and went to put a CD into the Spectral CD player in the system at the time.
The hum disappeared. Whaaa? I stepped back to look at the system and the hum returned. Haaaah? Sighing, I pushed the button to eject the CD and the hum disappeared. What the #*$%!?
Then I realized that when I had my hand on the CD player the hum stopped.
I was eliminating the hum by touching the CD player.
I called Harry down for our listening/testing session. I told him what was going on. He asked, “are you actually going to kneel there and keep your hand on top of the CD player the whole time we listen?” Having just gone through hours of troubleshooting while he was impatiently waiting, my answer was yes.
I learned something that day – if you hold your hand on a CD player for more than 10 minutes without daring to lift it off, it gets really uncomfortable. And since it was a hot day, after a while my hand started to sweat. As it did, the hum went down from faint to nonexistent. I became a better conductor as my hand got sweatier!
Then there was another time and another setup where I simply could not get the hum out of the turntable no matter what I tried. I built a spider-on-LSD web of wires connecting all the components. I disconnected every ground wire. I prayed to every deity I could think of. Finally, in a fit of anger I flung the turntable’s ground wire onto the carpeted floor.
The hum disappeared.
You’ve got to be kidding me. This isn’t possible.
I lifted the wire from the floor. The hum returned. I put the wire back onto the thick red carpet. (Harry was stylin’ in those days!) The hum disappeared. Carpet is supposed to be non-conductive.
I’m losing my mind. But in the interest of science, I started poking the end of the wire at various locations on the carpet. After a couple of minutes I found the spot where the hum was reduced the most.
Well, since I wanted to be professional about it, I soldered an alligator clip onto the end of the wire and clipped it to the carpet. Then I called Harry down to listen.
Of course, the first thing he spotted was the wire attached to the carpet. “What the heck is that?” I explained that it was the only way I could get the hum out of the system. I wish I’d had a camera to capture his look of utter disbelief. “Look, I’ll show you,” I said, and removed the clip…hummmm…
Partly to ensure that I wasn’t going mad, I conducted this demonstration for a number of guests over the next few weeks. They were as incredulous as I was. To this day, I have no explanation.
Today, I find grounding to be less of an issue, maybe because audio components are better. And I didn’t know what isolation transformers were (well duhhhh, but in my defense there weren’t many back then, and who knows what effect they might have had on the sound). Also, Harry was skeptical of power conditioners, which might have helped, and I don’t know if any power regenerators or battery-power systems existed at the time.