Summoning Elite Troubleshooters

Crosscheck

New member
Messages
14
New to forum. Please advise if I'm misstepping.

Symptom:
I'm at wit's end trying to kill a 60 cycle hum in my bass I had built last summer. It's been there from day one. I've spent several months speaking with different manufacturers, all who have provided great support (EMG, Audient, Source Audio, Furman, etc). I arrive here as a last ditch effort. I'll spare you the entire history unless you ask for it. Believe it or not, this is the distilled version.

My bass is pictured in my avatar. The electronics are as follows:

EMG J5 Active Pickups (although they are technically single coil, EMG says they are hum cancelling)
EMG BTC System Active Preamp
Double battery box, 7/8" jack and copper shielding from Warmoth. I did not realize at the time that shielding isn't needed with EMG.
Pig Hog braided patch cables.

The hum presents itself whether I'm playing through my Auident iD44, EBS Magni 500 2x10, Pedalboard with several Source Audio effects, or even just my Vox Amplug with headphones. It can be heard anywhere as I rotate in a 360 degree circle, save for two spots polar opposite of each other.

The fact that this same thing happens with the little Amplug just screams environmental (Clue #1?)

The bizarre thing is that it doesn't happen with my son's Ibanez FR700, or his Tobias Toby Deluxe IV, both active basses. What really kills me is that I went to a music room at the college my friend works at. We both plugged into my Audient, my bass hummed, and his Jazzmaster with passive single coils was quiet. What? How? (Clue #2?)

The point of this bass was to be a nicer version of the one Mike Lull (RIP) built for me in the 90s, which has since been stolen. Granted that was 25 years ago and electronics were American built. I'm now in a small New England town which is extremely crowded with old, crappy infrastructure compared to Seattle.

I took it to my luthier who built it. He tried rewiring the electronics, changed signal chain order, tried wiring the batteries both in serial and parallel, no difference. The one time we were able to have it quiet was plugged into an old giant Fender head and cab from the 60s (Clue #3?)

Before I had tested with the Vox Amplug, I bought a Furman PL-Plus DMC. No difference. The lion's share of troubleshooting has been with EMG:

They had me test each pickup independently, bypassing the Blend and BTC, No difference.
They had me change the signal chain order, no difference.
They had me rip out the shielding, no difference.
They had me send all the electronics, jack, battery box and patch cable I was using and they threw them on their bench. No hum. (Clue #4?)
They sent everything back along with some extra shielded coaxial cables and asked me to ground to the 2TEK Bridge, no difference.

I then visited a highly recommended electronics and amp wizard who's been running a shop with his luthier for 25 years. The noise did not significantly present itself at their shop, either in their amp or in my Amplug (yes, I brought it along). So we reached the conclusion that it is truly environmental. They also explained that the shielding was doing nothing, as it wasn't grounded.

SO. I ordered more shielding from Warmoth, took everything out, re-shielded the control & battery box cavities, and reinstalled everything. As EMG is mostly solderless, I can easily connect/disconnect the bridge ground. I also grounded the jack to the shielding. It sounds slightly better with the bridge ground disconnected, yet the hum still remains.

The conclusion I've sort of reached is that for whatever reason, my setup is highly sensitive. Yet I don't understand how I haven't found a way to shield it from the alleged environmental noise, and how - in the same environment - my son's low and midrange basses are quiet, as is my friend's Jazzmaster. This was supposed to be my dream bass. I've moved well past anger and am now just quietly defeated :(

Thanks to anyone who spends time on this thread.
 

mayfly

Senior member
Messages
8,228
Quick question:  Does the hum change when you touch the strings?

If not:
1 - did you ground the bridge?  Check with a multimeter to see.  Or, touch a metal part of the amp/jack/something that you know is grounded.  If the hum stops, then you didn't ground the bridge.

2 - I wonder if you have the hot and the cold leads mixed up at the output jack.  Another thing to check.
 

Crosscheck

New member
Messages
14
The only time the hum changed when I touch the strings, is the one time I accidentally put the bridge ground on the signal pin instead of the GND pin on the Volume pot. Currently everything is wired correctly, and there is no change when I touch the strings.

As I mentioned, I have a ground wire running to the bridge. As it has that modular connector, I can easily attach/detach it. It's slightly better ungrounded. However that is separate from the ground wire I have going from the jack to the shielding.

As for the leads running from the Volume pot to the jack, I've triple checked them and they match EMG's diagram. That said, I have not tried swapping them.
 

Chris Kinman

New member
Messages
3
There are 2 types of noise, Hum which is cancelled in the pickup and Buzz which can be minimized only by shielding the wiring cavities.

EMG pickups have internal shielding so grounding the strings is not necessary, the loss of sonic performance is compensated for by the active electronics inside the pickup.  Also EMG's are low impedance as is their active controls and that helps greatly to minimize hum.

It is indeed a perplexing mystery but somewhere there is something lurking that is causing this noise.  If it is indeed hum and not electrical buzz.  I can think of only one cause, ground loops.  In high impedance passive circuitry they are not a problem but can be present in active circuitry.  The usual solution to ground loops is star grounding, it's where all ground wires connect to a central ground point and like the tentacles of an octopus the other ends are not connected to anything (I.E. a ground point).  Include shielding connection too in this scenario just to be on the safe side.  It will be a tedious investigation but it might be worth it.

And just for the hell of it try a different lead.  Good luck.  CK
 

Rick

Senior member
Messages
4,311
if Every thing is done perfectly, including grounding, then there’s a defective part somewhere.  Whichever part, I don’t know.  I’d start by swapping out the the most complex parts and work my way to the simplest.  You could accumulate enough parts to make a new guitar, which isn’t the end of the world
 

mayfly

Senior member
Messages
8,228
Crosscheck said:
The only time the hum changed when I touch the strings, is the one time I accidentally put the bridge ground on the signal pin instead of the GND pin on the Volume pot. Currently everything is wired correctly, and there is no change when I touch the strings.

OK, I really wonder if you are picking up a bunch of EMI hash.  What happens is your body acts as an antenna picking up all the stuff in the air, which then it radiates directly into your pickups/electronics/etc.  Your body stops this when it is grounded - which pulls the EMI that your body has picked up to ground.  This is why you ground your bridge, so that your body is grounded when you play.

If touching the strings does not cure it, then try touching the (metal) plug when it's plugged into your amplifier - or just the (metal) chassis of the amplifier.

Do you have a ohm meter?  That will go a long way to help figure out what the heck is going on.
 

mayfly

Senior member
Messages
8,228
Forgot to ask:  can you post the wiring diagram that you used? And several clear photos of the actual wiring in the bass?
 

Chris Kinman

New member
Messages
3
Mayfly said this is why you ground your bridge, so that your body is grounded when you play.

Mayfly that's true of regular passive pickups but as I pointed out earlier, EMG's have internal shielding and you don't have to ground the strings, in fact, EMG advise against it.  At one time they made a big thing about this in their marketing saying their pickups protect you from being electrocuted because your body is not grounded and if you come into contact with a live microphone there is nowhere for the current to flow to ground.  I suppose it's true of their latest pickups too but they may have made some changes over the years, who knows?  CK
 

stratamania

Senior member
Messages
9,205
Indeed EMGs are not grounded to the bridge. The ones I have are not.

Are the connectors in the solderless system all connected the correct way up, which is in many cases may be what is intuitively thought of as upside down.

Be careful also of the assumption also of everything is correct. It might not be and such an assumption may lead to something obvious being missed.
 

Crosscheck

New member
Messages
14
You guys are rock stars. Excellent info here. I'm posting photos and I hope I'm addressing enough questions.

I did try swapping the leads at the jack, and the result was no sound at all. I assume this means I had it wired correctly.

Again, I have two ground wires; one from the bridge to the GND pin on the Volume pot (which sounds a little better ungrounded), and the other from the Sleeve tab at the jack to the shielding.

stratamania said:
Are the connectors in the solderless system all connected the correct way up, which is in many cases may be what is intuitively thought of as upside down.
They are indeed. Checked multiple times. All are facing up, save for the one connection going from the Blend to the BTC, which is by design supposed to be inverted at the BTC end.

Mayfly said:
OK, I really wonder if you are picking up a bunch of EMI hash.
Yes this is currently the leading theory. I mentioned that I have a ground wire going to the bridge. It is easily connected/disconnected due to EMG's solderless system, so it's easy to test. Ungrounded is slightly better. I don't have an ohm meter, but they do at the shop I took it to and they tested everything.

rick2 said:
if Every thing is done perfectly, including grounding, then there’s a defective part somewhere.
Unlikely, as EMG had every electronic component in my bass on their bench. It sounds fine out there in NW California, as well as places with cleaner power/better electrical wiring/less noise outside my home.
 

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stratamania

Senior member
Messages
9,205
There is not much obvious to see other than the grounding points where there is solder look a little dry. And the cavity to the output hole is itself not shielded.

Good looking bass... :icon_thumright:
 

Crosscheck

New member
Messages
14
stratamania said:
There is not much obvious to see other than the grounding points where there is solder look a little dry. And the cavity to the output hole is itself not shielded.

Good looking bass... :icon_thumright:

Hey thanks! Ya my soldering this time around is definitely ugly. I can't find my clip solder station or my flux. But the connections are at least solid. When I do a theater for someone, I can promise you it's much cleaner.

As for the output cavity, EMG recommended I keep shielding away from the jack. So I trimmed it back some.
 

stratamania

Senior member
Messages
9,205
They probably recommended it to prevent a possibility of shorting where the jack is. Though you could shield it and then insulate the shielding to prevent any shorting.
 

mayfly

Senior member
Messages
8,228
Yes nice looking bass.  I can't see anything obvious in the wiring either.  I would start a process of elimination:  Disconnect parts and see if the hum changes / goes away.  Start at the pickups and work your way up the signal chain.

And yes, where are you in the world?  Nothing like hands on when trying to debug something - and the arm of the Great UW stretches looooong.
 

Logrinn

Senior member
Messages
3,589
I would also like to add what’s been said before - ground loop.
If EMG doesn’t recommend grounding/shielding you have with the copper foil in essence created what could be a secondary grounding.
I would check this. Before you rip out the copper you could perhaps just remove the pots from the cavity and have them (and the output jack) dangling in the air and try it like that. If the problem disappears, well that’s good, and if it doesn’t at least you haven’t ripped out the copper foil in vain/error.
Could be worth a try.
 

mayfly

Senior member
Messages
8,228
Hmmmm - if you really do have secondary grounds wired in there, by accident or design, then yea that could contribute.  Might be easier to pull the ground leads off of the electronics one by one and see what happens than to pull the electronics out of the bass, but either will work...

Usually ground loops get noisy when your power is generated by something other than a battery (that is, plugged into a 50/60Hz wall outlet).  In usual hum cases, two pieces of equipment end up at different ground potentials because of those 50/60 current pulses they are dumping into their chassis grounds.  If you complete the loop, by connecting the same audio cable to both, then 50/60Hz current flows in the grounds of your sensitive parts of the circuit, creating the hum.  In your case though, it could be that if you've got a loop in your bass then the loop itself is acting as an antenna and picking up the EMI hash, then happily  transferring it to the grounds of your sensitive electronics.

Solution: break the loop- if ya got one.

Hmmmmm........
 

Rick

Senior member
Messages
4,311
Alright ... it's unlikely, but EMG could be wrong.  I'd start by getting rid of all that shielding.  You don't need that with EMG's and as Logrinn said, it could be the culprit.
 
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