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Post subject: HELP!!! Pedal Board Ground Loop Hum
Posted: Sat Oct 15, 2011 6:59 pm
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No good place for this in the Fender forums, so I thought I would try here since the smartest and best hang out here (cue giant suck up sound).

I appear to have a nasty ground loop hum in my pedal board.

I have two amps, a Fender Blues Deluxe Reissue and a Fender Champion 600. Both amps plug into a single Rotel power conditioner.

My pedal board is very simple: I have an A/B switch that I plug my guitar into. The B side of the switch goes to my Boss TU-3 tuner. The A side goes to a Fulltone Full Drive 2 MOSFET. I plug the output of the FD-2M into either amp. There is minimal hum in this configuration and most of that is from the Champion 600. Power to the pedals is provided by a Pedal Power ISO 5 with each pedal plugged into a separate, isolated output of the power supply.

Today I picked up a Electro-Harmonix LPB-1 to drive the Champion 600 leaving the FD-2M to feed the BDRI. I also picked up a Live Wire A/B/Y box to switch between the amps. My pedal board now goes:

1. Guitar into A/B box.
2. B output to tuner.
3. A output to input of the A/B/Y box.
4. A output of A/B/Y box to input of FD-2M
5. B output of A/B/Y box to input of LPB-1.
6. Output of FD-2M to BDRI.
7. Output of LPB-1 to Champion 600.

The result is a loud 60 Hz hum. Everything still works, but the hum is way too loud. The BDRI is the loudest source of the hum.

In trouble shooting I have found the following things:

1. In the A position of the A/B/Y box, turning the FD-2M on and off has no impact on the hum.
2. In the B position of the A/B/Y box, turning the LPB-1 on and off has no impact on the hum.
3. In the B position of the A/B/Y box, turning the FD-2M on and off results in a very large change in the hum level. With the FD-2M off, the hum is significantly increased.
4. With the A/B/Y box in the A position, unplugging the output of the A/B/Y box to the LPB-1 kills the hum.
5. With the A/B/Y box in the A position, unplugging the output of the A/B/Y box to the FD-2M resuts in a loud buzz, different from the hum.
6. With the A/B/Y box in the B position, unplugging the output of the A/B/Y box to the LPB-1 kills the hum.
7. With the A/B/Y box in the B position, unplugging the output of the A/B/Y box to the FD-2M resuts in a loud buzz, different from the hum.
8. Touching the case of LPB-1 in any postion of the of the A/B/Y box results in a buzz loverlayed on top of the hum.
9. I tried removing the ground wire in the A/B/Y box that runs to one of the switch bodies, but that had no effect on the hum.

HOW DO I FIX THIS??????? :(

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sat Oct 15, 2011 9:06 pm
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I wonder if it is because the C600 input jacks are connected to the chassis. :?:

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sat Oct 15, 2011 9:24 pm
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shimmilou wrote:
I wonder if it is because the C600 input jacks are connected to the chassis. :?:


I just checked with an ohm meter. Both the BDRI and C600 input jacks appear to be connected to the chassis

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sat Oct 15, 2011 10:18 pm
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Some additional tests I just ran:

I removed the A/B/Y/ box from my pedal board and connected the A output to the BDRI and the B output to the C600. I installed a battery and plugged a guitar into the A/B/Y box input.

I left the BDRI plugged into the power conditioner and plugged the C600 into three different outlets in the room. The result was a strong hum from the BDRI. It did not matter whether I selected the A or B output.

I left the BDRI plugged into the power conditioner and plugged the C600 into an outlet in another room that I know for a fact is a separate, dedicated line that runs from the outlet straight to the circuit beaker box. The result was a strong hum from the BDRI. It did not matter whether I selected the A or B output.

Turning off the C600 still results in strong hum from the BDRI when connected through the A/B/Y box. Only completely unplugging the C600 will cause the hum from the BDRI to stop.

I should also note that my large screen LCD tv is plugged into the same power conditioner. When both the tv and BDRI are on, there is no hum from either the BDRI or the tv.
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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sun Oct 16, 2011 12:43 am
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You might try a Radial Engineering Big Shot in lieu of the Live Wire A/B/Y. It has switchable ground lift and an isolation transformer that generally work well to eliminate ground-loop issues.

HTH

Arjay

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sun Oct 16, 2011 8:30 am
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bluesky636,

I could be wrong, but I thought that the BDRI and HRDlx both have the plastic covering the threads of the input jacks which isolate them from the chassis. You would still read a connection to the chassis because both the negative of the jack, and the chassis are connected to ground, but the jacks not connected to the chassis. Whereas on the C600, the threads are uncovered metal and make a direct connection with the chassis.

I am certain that my HRDlx has isolated input jacks, as I replaced them with Switchcraft jacks, and I noted that the original jacks are covered with plastic and were completely isolated from the chassis. I used fiber isolation shoulder washers with the new jacks to keep them isolated from the chassis. I don't know if the C600 jack holes are big enough for isolation washers or not.

You could even try removing power from the A/B/Y switch, it is only needed for the LEDs. Maybe also use batteries instead of the power supply for the pedals (just for a test). And further, you can eliminate the A/B switch and plug your tuner into the Y of the A/B/Y switch. You could also try a 2-prong adapter on the C600 power plug, just to see if that helps the noise, indicating that the C600 might be causing the noise. I would not use the amp with the ground lifted by the adapter, just for a test.

Although I don't know how/if any of this info would help, so you may need to get the "Big Shot" as Retroverbial suggested. I guess that my curiosity wants to know exactly what is causing the noise. I think that you are right, it is a ground loop, but where? :?

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sun Oct 16, 2011 8:54 am
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Location: Natural Bridge, Virginia
shimmilou wrote:
bluesky636,

I could be wrong, but I thought that the BDRI and HRDlx both have the plastic covering the threads of the input jacks which isolate them from the chassis. You would still read a connection to the chassis because both the negative of the jack, and the chassis are connected to ground, but the jacks not connected to the chassis. Whereas on the C600, the threads are uncovered metal and make a direct connection with the chassis.


You are correct about the metal threads on the C600 jack, but the bodies are plastic and I cannot tell if the threaded part of the jack is connected to anything in the jack body.

shimmilou wrote:
I am certain that my HRDlx has isolated input jacks, as I replaced them with Switchcraft jacks, and I noted that the original jacks are covered with plastic and were completely isolated from the chassis. I used fiber isolation shoulder washers with the new jacks to keep them isolated from the chassis. I don't know if the C600 jack holes are big enough for isolation washers or not.


Yes, the BDRI has the same type of input jacks. It would certainly be easy enough to drill out the C600 holes. Where do you get the isolation washers?

shimmilou wrote:
You could even try removing power from the A/B/Y switch, it is only needed for the LEDs. Maybe also use batteries instead of the power supply for the pedals (just for a test). And further, you can eliminate the A/B switch and plug your tuner into the Y of the A/B/Y switch. You could also try a 2-prong adapter on the C600 power plug, just to see if that helps the noise, indicating that the C600 might be causing the noise. I would not use the amp with the ground lifted by the adapter, just for a test.


Removing power or using a battery with the A/B/Y switch makes no difference.

I tried using the tuner to feed both amps and it made no difference.

I don't have a two-prong adaptor handy. Turning off the C600 makes no difference in the hum, but if I unplug it from power comlpetely the hum in the BDRI goes away.

shimmilou wrote:
Although I don't know how/if any of this info would help, so you may need to get the "Big Shot" as Retroverbial suggested. I guess that my curiosity wants to know exactly what is causing the noise. I think that you are right, it is a ground loop, but where? :?


I tried plugging the BDRI into other outlets and it made no difference.

I made a signal cable where the ground is disconnected at one end and tried it in different locations on the board and was able to achieve some hum reduction. I need to investigate this further, but I am not sure it is the final solution becasue when using this cable, touching the A/B/Y box foot switches with your hands creates a hum.

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sun Oct 16, 2011 10:35 am
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Yes, plastic body is only a cover, I think that the part of the jack that mounts to the inside of the chassis is metal. If, after you verify, the jacks are connected to the chassis, that is definitely a ground loop. Impossible to say if this is the loop, but a loop. I didn't try the C600 with pedals, and I didn't try the isolation washers because not much noise at all by itself. Maybe the pedal amplifies the noise that the amp already has?

The washers are from Mouser, one shoulder and one flat for each jack. The same washers will work for the C600, except as you mentioned, the chassis hole size. :?:

Shoulder:
http://www.mouser.com/ProductDetail/Keystone-Electronics/3069/?qs=l8Mz4RVwyflRu0gEeXTRvw%3d%3d

Flat:
http://www.mouser.com/ProductDetail/Keystone-Electronics/3222/?qs=zfzUrXoPZmiqhiSt05vgkw%3d%3d

It seems that you are isolating the issue, eliminating the pedal power supply and other parts. It's hard to predict or even find grounding issue causes sometimes, if that is what the problem is. I think that the idea of isolating the input jacks from the chassis came from noise introduced when amps started using a ground. At the same time, I have replaced many 2 prong plugs with 3 prong grounded plugs on amp's that had the jacks connected to the chassis with no noise introduced at all, so this may be wild goose chase. This might be why the Big shot is used, it is a lot easier than screwing around with the amp. :?:

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sun Oct 16, 2011 5:19 pm
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I took a chance today and bought a Hum-X at my local Guitar Center. Actually, I bought two just in case. I unplugged my BDRI from the power conditioner and plugged it into the Hum-X and then into the wall outlet. The hum in the BDRI disappeared! Plugging the C600 into the second Hum-X resulted in no further improvement, so I will return one of them for a refund. There are, however, a couple of other anomolies that have appeared:

1. I have the pedal board connected to each amp with 10' Planet Waves cables. I first used a 20' Planet Waves cable to connect the guitar to the input A/B switch on the pedal board. Using that cable, I began picking up a radio station, something that has never happened before. Also with the BDRI selected and the FD-2M active, turning the volume of the guitar all the way down resulted in a "putt-putt" motorboating sound from the BDRI. Turning the volume up slightly got rid of the motorboating. I located a 15' Planet Waves cable of the same type and used that. Both the radio station and motorboating disappeared, but the amp seemed a little bit hissier than before. I have ordered a 10' Planet Waves cable of the same type to try that. My total cable length from guitar to amp would be about 22' with the 10' input cable.

2. The most annoying anomoly is with the BDRI selected with the A/B/Y box and the FD-2M turned on, switching to the B output of the A/B/Y box (driving the C600) and not turning the FD-2M off, results in a nasty buzz from the BDRI. Turn off the FD-2M and the buzz goes away.

I went ahead and ordered 100 of the jack isolators from Mouser to try when I take the C600 apart for its mods. I figure it couldn't hurt.

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Sun Oct 16, 2011 9:43 pm
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Problem Solved!

There is definitely something wrong with the A/B/Y box. Maybe that's why the guy had it for sale at the guitar/amp show after using it for only a few weeks. :lol:

I pulled the A/B/Y box out and moved the A/B box that I used as an input splitter to where the A/B/Y box was. Now I plug directly into the tuner, the tuner output feeds the input of the A/B box, output A goes to the FD-2M/BDRI and output B goes to the LPB-1/C600. I left the BDRI plugged into the Hum-X and the C600 and pedalboard power supply are plugged into the power conditioner. The result?

No hum.

No buzz from the BDRI when the FD-2M is left on and the input is switched to the C600.

No errant radio stations.

In short, no noise except a very low level hiss no louder than my original pedalboard configuration.

I'm going to check the A/B/Y box out when I get a chance this week to see if there is a bad ground or other wiring problem inside. But as it is now, I am back in business and able to switch silently between either amp.

Whew!

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Post subject: Re: HELP!!! Pedal Board Ground Loop Hum
Posted: Mon Oct 17, 2011 7:25 am
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I ran into a similar problem trying to use my Blues Deluxe and Blues Junior in a stereo configuration. I finally was able to tame it with an EbTech two channel Hum Eliminator using just one of the channels going to one of the amps. I knew it was a ground loop hum, because if I used a two prong adapter on one of the amps the hum went away, the EbTech does it a lot safer though.

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