Loud HUM through PA speaker

jkilgour2000 · #1 06-26-2017, 08:32 AM

Hey Guys! I'm kind of new around here, but I have a situation that's a head scratcher for me, and was wondering if anyone had any answers?

Here's the setup, and it's pretty simple:

I'm plugging in my acoustic guitar directly to the Zoom A3 Pre-Amp. The sound this little box makes is amazing!

The connection is made with a high-quality shielded un-blanced guitar cable. The A3 is then sent to a PA speaker (specifically the SAMSON Expedition XP106w). This is a great little portable 100w PA. That's it.

I've tried to connect to this PA 2 different ways.

The first way is using the 1/4" mono out of the A3 directly to either the 1/4" Line input on the PA, or the 1/4" Guitar input on the PA.

The second way is connecting the headphone out (1/8" Stereo) of A3 into the back of the PA where you can connect an aux music device, such as an iPod.

With any of this connections, I get a loud HUM. Not a BUZZ like you would hear from some electric guitar pickups, but a HUM.

The guitar I am connecting is a Taylor 322ce with the ES2 system. It has a fresh battery, and even swapping batteries there is still the hum.

The kicker is this:

If I pull the plug on the back of the PA, and run it in battery mode, this HUM goes away. Strange, because it's plugged directly into a high-quality surge protector. The plug on the back of this Samson PA is a two-prong wall-wart.

If I disconnect the PA, and plug in headphones to the A3 out (which is the same jack used to connect it to the PA), there is no hum and it's dead quiet (in the headphones)

If I connect my other guitar, which is a Taylor 324 with LR Baggs Lyric system, to the PA (all inputs) there is no hum, and it's nice and clean. I get the same result with my Yamaha, which has the Seymour Duncan Mag Mic: no hum.

I'm confused to say the least! Any isight on this would be helpful. This is a great PA for busking, and i want to stick with it (bought the thing yesterday). This issue seems to be just with 322 with the ES2 system.

However, if i connect the 322 DIRECTLY to the back of the PA (no A3), it's clean.

Thanks in advance to any suggestions you might have..

--John

H165 · #2 06-26-2017, 08:54 AM

Safety first - if you're gonna mess with this stuff, be careful.

That's probably 60 cycle hum introduced by the lack of a ground. So, somewhere in the power 'signal chain' your power supply (probably the two-prong wall-wart) is not grounded. You may have an ungrounded neutral at that particular plug. Try the system at a different plug and see what happens. If things improve, go get yourself one of those three-LED testers and stick it in the offending plug. That will tell you the problem (don't try to fix it unless you know how to do it safely).

If the problem persists regardless of plug, test the wall-wart. Borrow someone else's power supply wall-wart, and see if the same thing happens. Be careful.

Al Acuff · #3 06-26-2017, 08:58 AM

Are you plugging everything into a single power strip going to a correctly wired outlet?

If you plug your speaker and processor into different outlets you can create a ground loop.

zhunter · #4 06-26-2017, 09:04 AM

Ground loop is likely. Are you powering the Zoom from the wall wart or batteries? Try powering it with batteries. Also there is a ground lift button on the Zoom. While powering from the wall wart, depress it and lift the ground.

Unfortunately the surge protector won't help with a ground loop. Sometimes you can minimize the hum by plugging every thing into the same outlet location but not always.

hunter

jkilgour2000 · #5 06-26-2017, 09:39 AM

Quote:

Originally Posted by Al Acuff

Are you plugging everything into a single power strip going to a correctly wired outlet?

If you plug your speaker and processor into different outlets you can create a ground loop.

The only thing plugged in is the PA. The Zoom is running off the batteries.

rmp · #6 06-26-2017, 09:51 AM

These can be a nuisance and hard to sort out.

Does the setup do this all the time? Do you move the system at all (like to other places besides home?

How old is the pickup system in the acoustic? you'd be surprised, but they don't last forever.

There's a line of crystals that separate the elements, over time, these compress form the stress of the strings pushing down on the bridge and the pickup is then prone to some grounding problems. (I had a similar problem with a Fishman Natural pickup, it was about 20 years old when it started.)

if yours is relatively new, it's probably ok.

If you touch the jack when it's plugged in, does it stop?

It can also come and go, since the grounding can behave differently with different electrical services, and plugs.

My buddy has an older Takamine that has a pretty loud hum sometimes, it doesn't do it every where he takes it but it's been something we've had to try and deal with.

ljguitar · #7 06-26-2017, 10:14 AM

Hi John

I carry a 3 prong to two prong adapter with me with all my amps, and my PA rig. When the hum shows up, we put the adapter on the plug and it usually lifts the ground and kills the hum.

Been doing this for over 30 years. It's not technically 'correct' but it works and doesn't damage equipment (much modern equipment is moving back to two prong plugs in USA). I've had hum on million dollar stages that my 3-to-2 adapter fixed. One sound tech asked for mine (it cost me less than a dollar) so I left it with him.

I used to work hard to 'resolve' hum only to discover the venue had a coffee pot plugged into the same circuit, or their 'OPEN' sign, or some other piece of gear. The 3-to-2 adapter works about 95% of the time.

I'm prepared for the nay sayers to tell me the potential harm to my body. Never been shocked or broken any gear. I'm careful for my gear, and the places I play may have out-dated wiring now, but it was wired to code to begin with (in the 1930s or 1940s).

Hope this adds to your choices…

jkilgour2000 · #8 06-26-2017, 10:24 AM

Quote:

Originally Posted by rmp

These can be a nuisance and hard to sort out.

Does the setup do this all the time? Do you move the system at all (like to other places besides home?

How old is the pickup system in the acoustic? you'd be surprised, but they don't last forever.

There's a line of crystals that separate the elements, over time, these compress form the stress of the strings pushing down on the bridge and the pickup is then prone to some grounding problems. (I had a similar problem with a Fishman Natural pickup, it was about 20 years old when it started.)

if yours is relatively new, it's probably ok.

If you touch the jack when it's plugged in, does it stop?

-- Yes

It can also come and go, since the grounding can behave differently with different electrical services, and plugs.

My buddy has an older Takamine that has a pretty loud hum sometimes, it doesn't do it every where he takes it but it's been something we've had to try and deal with.

-- The PA is brand new. I'm plugging it into an AC plug that i have used for years (recording studio) without issue

--It's a new guitar, purchased in January - Taylor 322 with ES2

-- Yes if I touch touch the jack when it's plugged in it stops

YamahaGuy · #9 06-26-2017, 10:25 AM

When connecting the Zoom to the PA, are you using an instrument cable? I was just at a gig and a guy with a ES2 812ce had a similar problem. Come to find out, he was using a speaker Cable from his multi-effect unit to to the DI. With an instrument cable, problem solved.

Why aren't you using the XLR output? Especially since it has the ground lift. For me, I've found the XLR output to have the cleanest signal into a PA.

jkilgour2000 · #10 06-26-2017, 10:25 AM

Quote:

Originally Posted by ljguitar

Hi John

I carry a 3 prong to two prong adapter with me with all my amps, and my PA rig. When the hum shows up, we put the adapter on the plug and it usually lifts the ground and kills the hum.

Been doing this for over 30 years. It's not technically 'correct' but it works and doesn't damage equipment (much modern equipment is moving back to two prong plugs in USA). I've had hum on million dollar stages that my 3-to-2 adapter fixed. One sound tech asked for mine (it cost me less than a dollar) so I left it with him.

I used to work hard to 'resolve' hum only to discover the venue had a coffee pot plugged into the same circuit, or their 'OPEN' sign, or some other piece of gear. The 3-to-2 adapter works about 95% of the time.

I'm prepared for the nay sayers to tell me the potential harm to my body. Never been shocked or broken any gear. I'm careful for my gear, and the places I play may have out-dated wiring now, but it was wired to code to begin with (in the 1930s or 1940s).

Hope this adds to your choices…

I will try this method. It's strange though, because the plug on Samson is essentially a "wall-wart", and doesn't have 3 prongs.

jkilgour2000 · #11 06-26-2017, 10:26 AM

Quote:

Originally Posted by YamahaGuy

When connecting the Zoom to the PA, are you using an instrument cable? I was just at a gig and a guy with a ES2 812ce had a similar problem. Come to find out, he was using a speaker Cable from his multi-effect unit to to the DI. With an instrument cable, problem solved.

Yeah, I tried that with another 1/4 guitar cable i had. The hum was the same.

jkilgour2000 · #12 06-26-2017, 10:28 AM

Do you think sticking one of these:

https://www.amazon.com/EBTECH-HE-2-E...Hum+Eliminator

In the signal path might correct it?

YamahaGuy · #13 06-26-2017, 10:34 AM

I think sometimes those hum eliminators are a waste of time and money. I'd try the XLR out before throwing any more money at the problem.

jkilgour2000 · #14 06-26-2017, 10:42 AM

I never thought of that (I actually forgot there was an XLR out of the zoom!). I will try that tonight!

jkilgour2000 · #15 06-26-2017, 10:44 AM

Quote:

Originally Posted by YamahaGuy

When connecting the Zoom to the PA, are you using an instrument cable? I was just at a gig and a guy with a ES2 812ce had a similar problem. Come to find out, he was using a speaker Cable from his multi-effect unit to to the DI. With an instrument cable, problem solved.

Why aren't you using the XLR output? Especially since it has the ground lift. For me, I've found the XLR output to have the cleanest signal into a PA.

I'm going to try the XLR ... I had forgotten about that! Hopefully this will be the fix .. I'll report back