the dreaded 60 cycle hum

Al Moss · From: Kent,OH,USA

-played a gig the other night at an old theater. As is not that unusual, our gtr player plugged in his Super 400 with a DeArmond pickup into a Vibrolux and the dreaded 60 cycle hum was even louder than usual. I brought my noiseless EMG pickup Tele to the gig and even that had a 60 cycle hum, not as loud as the Super , but still there. ..And, even my BL 710 pickups in the Mullen were humming a bit too. We tried the usual remedies, different outlets, ground lifts, (couldn't do much with the theater production stage lights, - on faders - that were probably the source of the noise) I'm wondering if there is an effective way to diminish the presence of the dreaded hum, and if anybody could advise. I was attracted to the new piece of Furman gear called the Power Factor Pro ($220.00/street) that advertises a massive cleanup of noisy AC and a constant flow of clean 110 to our gear. -went to HarmonyCentral.com and read a less than glowing user review of its' cleanup abilities. Any thoughts?

Ray Minich · From: Bradford, Pa. Frozen Tundra

If those stage light dimmers were the old saturated core reactors you probably had enough 60 cycle EMF in the air to power a small car. Kinda like trying to play next to a power company substation.

[This message was edited by Ray Minich on 11 August 2004 at 07:39 AM.]

C Dixon · From: Duluth, GA USA

Dead on Ray,

And if so, you can give your amp, cables, volume control anything you "wont" to, including mother's milk; and dat blasted hum gunna be there. Cuz dat PU in most likelyhood be the part that is pickun up that behemoth unwanted intruder.

However, there are some devices on the market that are designed to reduce 60 cycle hum. But I do not believe there is a chance any of them would not creat a "suck out of the fidelity of your system."

And while hum is a real bear, PSG players' ears are sooooo very sensitive, IMO, tis better to live with the hum than the loss of given frequencies in the audio spectrum, including those very necessary harmonics of 60 cycle musical notes.

May Jesus bless you in your quests,

carl

John Daugherty · From: Rolla, Missouri, USA

I think Ray and Carl are correct. You are probably stuck with the hum until they get rid of the dimmers.
If you can find a 120vac power line filter to plug your equipment into, it would be worth a try. ...JD

[This message was edited by John Daugherty on 11 August 2004 at 09:41 AM.]

Bill Ford · From: Graniteville SC Aiken

I know Carl probably wont remember this, but we used to wrap everything in tinfoil(this was before aluminum foil), I seem to remember it helping some on concrete floors,if you covered the pickup,would it work to stop airborn signals?

Bill

[This message was edited by Bill Ford on 11 August 2004 at 01:08 PM.]

Donny Hinson · From: Glen Burnie, Md. U.S.A.

With the way that electronics has advanced in the past few years, I'm really AMAZED that no musical amp manufacturer has put a 60-cycle notch filter in their amplifiers. About $3 worth of parts could put that offending hum 30db down.

Al Moss · From: Kent,OH,USA

Sounds to me from your suggestions that the properties of old timey stage light dimmers are the real culprit here in exacerbating already problematic pickups like the old DeArmond single coil. Still I was surprised that the noise came through on my EMG's and a bit on the steel. This was a real time capsule of stages, a restored Masonic Hall, privately owned and operated now, but really like walking back 50 or more years upon entry. I believe that the restoration would have required modern electric codes to be observed but maybe not those old dimmers.

Ray Minich · From: Bradford, Pa. Frozen Tundra

A saturable core reactor is a big azzed transformer with a third winding. You vary the saturation level of the core by passing a current thru the third winding. At max current thru the third winding the core is saturated and the transformer action is "pinched off". These transformers run hot and gotta be big to handle the heat and the load. Thus, the analogy to playing your gig next to a substation. Similar xfmr behavior is seen in modern day Constant Voltage Stabilized transformers like those made by SOLA or TOPAZ where the core is run in partial saturation. That's why they hum like a bee and need big cooling cages.

[This message was edited by Ray Minich on 11 August 2004 at 07:33 PM.]

[This message was edited by Ray Minich on 11 August 2004 at 07:34 PM.]

Susan Alcorn · From: Baltimore, MD, USA

I've been having quite a bit of trouble with that myself. I bought the two Hum-X products and it didn't help. Really annoying.

Dixson Rudolph · From: Dodson, Louisiana USA

I recently found a 'Line Tamer' 120 V isolation xfmr at a local thrift store for $5. It's a fairly heavy (of course...it's just a big 1:1 TRANSFORMER), and it's not big enough to run the whole PA through (only 700 VA) but for a steel or guitar amp, it eliminates hum due to 'DIRTY' power at the wall socket.
It's sure saved MY butt on more than one gig!
Keep checkin' those yard sales, thrift stores, etc. Ya never know what you might find.
Just my $.02

Dave Boothroyd · From: Staffordshire Moorlands

The reason why Amps don't come with a 60 Hz notch filter is that it would not work.
We work with 50 Hz over here, but if I use a Graphic EQ to cut out mains frequency it makes hardly any difference to the loudness of the hum. That's because the fundamental 50 or 60 Hz is not very perceptible anyway- we are not built for bass- what you are mostly hearing are second, third and fourth harmonics- and more, especially odd ones, if there is any clipping anywhere in the system.
So you would need to notch out 120Hz, 180Hz, 240Hz as well- which would mean that you may as well leave your lower four strings at home!

------------------
Cheers!
Dave

Earnest Bovine · From: Los Angeles CA USA

Another reason that a 60 Hz notch filter wouldn't work is that most of the bad hum you hear is not 60 Hz, but rather multiples (harmonics) of 60; i.e. 120 Hz, 180 Hz, 240 Hz, etc., which would pass right thru the notch filter.
It seems to me that you could eliminate all of those frequencies from any audio signal simply by delaying the signal by exactly 1/120 second, inverting its polarity, and adding the delayed+inverted signal to the original at the same amplitude. That should cancel 120 Hx and all its harmonics.
Whether it would mess up your sound is another matter, but seems to me that it would sound better than any filter, because the band(s) it eliminates would be extremely narrow.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Sorry guys, I don't buy that "harmonics are the worst offenders" theory. (My oscilloscope tells me differently.) The 60-cycle fundamental is by far the most troublesome, and it's well within our hearing range. In fact, that's significantly higher than the low "E" on a bass guitar.

Nice try, though.

[This message was edited by Donny Hinson on 15 August 2004 at 08:20 AM.]

T. C. Furlong · From: Lake County, Illinois, USA

Donny, sorry but I buy the 120/180/240 thing. I have demonstrated more than once in actual show conditions that a harmonic of 60Hz is the most noticable thing in a typical "60 cycle" hum. I had a bugger of a 60 Hz hum that I could not eliminate with usual troubleshooting. This was in a TV studio sound system with a national artist arriving for rehearsal and taping of a concert special. Dimmers everywhere, feeder laid on audio snakes at the last minute and that's the tip of the nightmare. So anyway I'm getting pretty desparate so I get a spare XTA DSP loudspeaker management processor, set one filter at 1/20th of an octave (notch), set the frequency at 40Hz a start sweeping up without looking at the display until I hear any sort of improvement. I went past 60Hz past 120Hz no big change. Then like magic I get somewhere higher and the hum is gone! I look at the display and frequency is 180.00. So then I set it at 181.00 and guess what, hums back. Same deal with 179.00.

Now I know that many other factors were part of this situation. Room acoustics, masking of other frequencies by other ambient noise sources, electro-acoustic phase cancellation etc. but it's pretty clear to me the fundamental in not the only thing to look at.

TC Furlong

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Thanks for your input, TC! Okay, there may indeed be cases where a harmonic is the problem. Cheap incandescent dimmers (the kind whose output component is basically a square or sawtooth wave) are literally chock full of harmonics. My whole point was that amp manufacturers have done nothing to help us with the problem. However, as you so clearly pointed out, a tunable notch filter would work! So, why can't they give us one to help with hum problems?

T. C. Furlong · From: Lake County, Illinois, USA

Donny,

I agree that a sweepable notch filter would help but one that wouldn't destroy S/N ratio and phase response would add way too much cost to a steel or guitar amp. Roland used to make a digital hum canceller that works great. The device works like this. You dial in the line frequency and it adds deep notches at the fundamental and all of the harmonices. I forget the model # but it's cool.

Earnest Bovine · From: Los Angeles CA USA

Drawing a picture I see that the delay time must be 1/60 second, not 1/120 second. That's 0.016666 seconds (0.2 seconds for you Europeans and Mexicans). Surely somebody has a delay box that lets you invert the delayed signal.

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