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ideas on reducing mains hum with single coil guitar pickups Effects Pedals, Units & Accessories
Old 28th October 2011
  #1
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jackinthebox's Avatar
 

ideas on reducing mains hum with single coil guitar pickups

are there any clever ways to reduce single coil hum on a telecaster in a live on stage situation? I know about shielding the internal cavities of the guitar with copper foil, and fitting humbuckers of course but i'm wondering if there is some way of balancing the signal or disconnecting the earth/ground so it doesn't get to the amp. Maybe a DI box close to the guitar and a reamp box by the amp?
I have a show next week at shepherds bush empire in london which is always a problem for mains hum.
Any advice gratefully received.
Thanks in advance.


Jack
Old 28th October 2011
  #2
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jp22's Avatar
 

Quote:
Originally Posted by jackinthebox View Post
are there any clever ways to reduce single coil hum on a telecaster in a live on stage situation? I know about shielding the internal cavities of the guitar with copper foil, and fitting humbuckers of course but i'm wondering if there is some way of balancing the signal or disconnecting the earth/ground so it doesn't get to the amp. Maybe a DI box close to the guitar and a reamp box by the amp?
I have a show next week at shepherds bush empire in london which is always a problem for mains hum.
Any advice gratefully received.
Thanks in advance.
Jack
You're stating this issue as if there's a grounding problem only within that particular venue being played, which isn't completely believable, but still possible I suppose. If you're still convinced though, then personally, I don't think it's so much as stopping the hum "before it gets to the amp" as it is before it gets to the speaker, regardless of where it's coming from. The goal then should obviously be to try stopping it before it reaches the speaker, so put something in between the amp and the speaker input to eliminate it before reaches the speaker. There are several different types of hum elimination devices made, pedals, racks, isolators, etc.. I would also be sure you're using a good expander/gate.
Old 28th October 2011
  #3
In really bad situations, this always works for me:
EHX.com | Hum Debugger - Hum Eliminator | Electro-Harmonix
Old 28th October 2011
  #4
It comes from the tele pickups, everything downstream is moot. You can test that yourself, turn down the guitar to 0, noise gone? Screening the guitar is very effective in removing buzz noise, 500 hz and up. Done well you can take your hands off the strings, no buzz.

Hum is more complicated. That comes up at 60, 120, 183 and 250 hz in the 60 hz countries. Finding "Mecca" on stage is problematic as cross magnetic fields are always present in larger facilities.

The solution is in the pickups. Use stacked humcancelling pickup designs. Use shielded wire, not that 2 wire Fender stuff.

In my Telecasters I developed a hum cancelling circuit using a Jap strat dummy coil. It has a hum trimpot that nulls at the center. This active design gets an 80 db s/n ratio, pretty good for a Telecaster. Output levels are 10 db hotter and low impedance to overcome cable effects. Combined with shock mounted pickups, I get Hendrix levels of feedback and no Tele squeals.
Old 28th October 2011
  #5
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I've seen peeps afix a conductive wire between their git's bridge and their own body. Seen this fix a nasty buzz when nothing else would do the trick on the spot in the field.
Usually you can just add an ebtech thingy or hum-x or whatever eliminator.

If this is an ongoing problem, it could be a sign your signal chain needs airing out, or your git needs a workover...

Oh! I like Jim's rig above! So with that trimpot, you can dial in the cancellation? Cool.
How do the shockmounts add to the picture?
Old 29th October 2011
  #6
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DarkSky Media's Avatar
Quote:
Originally Posted by Jim Williams View Post
The solution is in the pickups. Use stacked humcancelling pickup designs. Use shielded wire, not that 2 wire Fender stuff.


The better stacked designs keep the single-coil sound but without the hum. I'm partial to Kinmans, but SD do them well also.
Old 29th October 2011
  #7
Quote:
Originally Posted by Boschen View Post
I've seen peeps afix a conductive wire between their git's bridge and their own body. Seen this fix a nasty buzz when nothing else would do the trick on the spot in the field.
Usually you can just add an ebtech thingy or hum-x or whatever eliminator.

If this is an ongoing problem, it could be a sign your signal chain needs airing out, or your git needs a workover...

Oh! I like Jim's rig above! So with that trimpot, you can dial in the cancellation? Cool.
How do the shockmounts add to the picture?
Buzz from body presense is easy to fix. If the pickups and cavity is not screened under the pickups, your body will generate buzz when the guitar is worn. Push the body away and that buzz goes away. Wrap copper foil under all the pickups and it's gone.

A string ground should always be fitted. I use a .022uf cap in series with the string ground. That shunts the buzz frequencies but blocks 60 hz so you won't get electrocuted. I do get a kick watching vocalists get a nasty shock on stage while I never do. Every electric guitar should have that feature added. I found death is bad for repeat business. How does Gibson/Fender still get away with that under OSHA?

The hum cancelling preamp has 2 inputs, one is for the pickups, the other is for the dummy coil. The dummy coil is filtered so everything above 3 k hz is filtered out. That feeds a trimpot and the signal is combined and tunes out hum frequencies via phase cancellation. It's a small 1" square PCB that fits between the volume/tone pots on my Telecasters. A second trim pot sets gain from +6 db to + 26 db, I set it at + 10 db. The battery fits below in the control compartment. In my Thinline and Rosewood Tele's there's room in the control cavities to mount the dummy coil there. On the other Tele's I routed out a space under the pickguard for it. It's fully screened in copper tape, soaked in wax to control microphonics and all the pickups are mounted using latex surgical hose for mechanical damping. That avoids the pickups moving and causing squeals. The lead pickups have their steel plate under them removed, that's another squeal source. I use 6/32 lock nuts instead.

Removing the steel pickup mounting springs and using latex surgical hose avoids another squeal source, anything magnetic that can move will feedback at a high enough volume. Hendrix proved this as the older Strats he used were very stable, they used latex to mount the pickups. Later models in 1968 went to springs and those guitars are harder to control.

Lastly, the bridge is glued down on the edges with silicon glue. Tele bridges tend to pull up a bit by the pickguard, tap on it there and you can hear if it's not solid against the wood. The glue dampens any metal that can move. Remember, if it's steel or magnetic and it can move, it will squeal.

The results are I can set my 120 watt Basson Sound stack all the way up to Hendrix live levels and no squeals, just controlled feedback. Hold the strings and no noise either.
Old 29th October 2011
  #8
Gear Head
 

I've got an ISP decimator that does the trick pretty well.
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