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So your bass has a hum

#201
Manny Bernardez said:
Intrigued by this as well I just received my first Ric in a trade and find it very uhmm... Hummy? Even with both pickups open (unlike any other 2 pickup bass guitar I've ever owned). I have not had the time to open it and see how it's wired. But wondering if this is just part of the Ric sound or if I just need to better ground this beast?
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Ric single-coil pickups are not wound to be hum canceling. They don't work like a jazz. While grounding and shielding helps, it's not going to solve the 60Hz hum if you're having a problem with it. The best way to solve that issue is to replace one or both pickups. Companies that make replacement Ric pickups include Nordstrand, Bartolini, Classic Amplification, Sentell, and Joe Barden Engineering. (There may be others, but those are the ones I know about.) The Nordstrand pickup is designed to replace the neck pickup and be RWRP with the existing bridge pickup, thereby eliminating the hum when both pickups are used together. Classic Amplification may also do that, but I'd contact them first (I know they make single-coil sets that cancel hum when used together). The Barts, Sentell, and JBE are hum canceling pickups, so if you get just one to match with one of your Ric pickups, you still might have some hum.
 
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#202
Manny Bernardez said:
Intrigued by this as well I just received my first Ric in a trade and find it very uhmm... Hummy? Even with both pickups open (unlike any other 2 pickup bass guitar I've ever owned). I have not had the time to open it and see how it's wired. But wondering if this is just part of the Ric sound or if I just need to better ground this beast?
Click to expand...
As @BlueTalon pointed out, Rickenbacker pickups are not wound "RWRP" like Jazz Bass pickups and are actually hum-adding rather than hum-bucking when you have both on. Fortunately it is pretty easy to mod one of the stock pickups in order to make the set function like RWRP pickups. Another TB'er made a pictorial of the process at one point. Peruse later in the thread for some more info and pics of the mod with the more modern Rick pickups with adjustable poles (you need to flip one of the magnets and these poles actually screw into them on modern Ricks, so requires a tad more care than the pickup modded in the first post): [Rickenbacker 4003] RWRP Bridge Pickup Mod Tutorial

If you otherwise aren't happy with the tone of your stock pickups, then there are a number of replacement options that also will resolve this issue. The Nordstrand Nordenbocker neck pickup is a single coil specifically designed to both give you a better volume balance and hum-cancelling when paired with the stock bridge pickup (as the stock neck pickup is always inherently much weaker), the Classic Amplification single-coil sets can be ordered RWRP and are what I use in my Ricks for more of a vintage-Rickenbacker flavor, there are also full humbucker pickup sets like the Seymour Duncan, Bartolini, and Barden Rickenbacker options as well as an array of options from Creamery Pickups in the UK...
 
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#204
I have a related question. I am trying to install the Xotic HRI (Hum Reduction Inductor) into my early model Xotic XJ-1t 5 string. My harness is vol 1 push/pull (active/passive), vol 2 push/pull (series/parallel), and master tone. The installation instructions provided by Xotic has the same basic layout with push/pulls, etc. However, the wiring is different. I spent three days trying different locations to attach the wires from the HRI and none made it work. So I spoke with a well known luthier. He told me the problem is hum reducers will not work on series circuits. The harness must be parallel first. Then you can add options except for series! Is this true? Thank You! Larry
 
#205
Larry Balara said:
I have a related question. I am trying to install the Xotic HRI (Hum Reduction Inductor) into my early model Xotic XJ-1t 5 string. My harness is vol 1 push/pull (active/passive), vol 2 push/pull (series/parallel), and master tone. The installation instructions provided by Xotic has the same basic layout with push/pulls, etc. However, the wiring is different. I spent three days trying different locations to attach the wires from the HRI and none made it work. So I spoke with a well known luthier. He told me the problem is hum reducers will not work on series circuits. The harness must be parallel first. Then you can add options except for series! Is this true? Thank You! Larry
Click to expand...
I guess the “HRI” is just a dummy coil that cancels out the noise when one of the pickups is selected? And your bass has single coil pickups that are humcancelling when both are turned up all the way? If so, there are multiple ways to wire a dummy coil that will change the function. You can run a dummy coil in parallel or in series with whichever pickup you are trying to cancel hum from, and depending on which pickup you were pairing it with you would need to reverse the phase of the dummy coil.

A dummy coil shouldn’t be needed in series mode of a standard single coil J-bass because the two pickups already cancel hum when used together (and in series they are both on 100%). A dummy coil used in series would just add noise rather than doing anything beneficial. The same would be true when running both pickups on in parallel mode.

Does the HRI usually only cancel the noise from one specific pickup (only neck or bridge)? Or does it work with either pickup soloed? If B, then there must be some sort of phase switching happening (or multiple dummy coils).

Also possible the winding of this dummy coil doesn’t match the particular pickups of your bass (either resistance or phase). Try reversing the +/- phase of the dummy coil and see if that helps at all.

Can you post any documentation/wiring diagrams for this “HRI”?
 
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#206
Thank You for your reply. I just found out from Xotic that the HRI turns off when in series mode. The hum is present when either pickup is soloed but not when used together. Also, Xotic says the HRI unit needs to be infor a seperate cavity under the pickguard for distance. However, the luthier I spoke with says if the control cavity has room it can go there. I have attached the installation diagram provided by Xotic. It is labeled series however the wiring is not the same as my bass.
 

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#207
Larry Balara said:
Thank You for your reply. I just found out from Xotic that the HRI turns off when in series mode. The hum is present when either pickup is soloed but not when used together. Also, Xotic says the HRI unit needs to be infor a seperate cavity under the pickguard for distance. However, the luthier I spoke with says if the control cavity has room it can go there. I have attached the installation diagram provided by Xotic. It is labeled series however the wiring is not the same as my bass.
Click to expand...
Interesting- it looks like this may actually be two dummy coils, so that either pickup can benefit from noise cancellation when soloed. Pretty cool! The pickup coils here are both run in series with the dummy coils (the ground connection from each pickup runs through the inductor to ground), so I don’t think you’ll be able to install the HRI effectively in your bass without swapping the wiring to match this diagram, at least as far as the switches are wired. I can’t tell what the red wire from the HRI is, though maybe it is an active device that requires power.
 
#210
I have attached a picture of the control cavity. The pickups are wired black wire from the neck pickup to the top of vol 1 and white wire from the bridge pickup to a pole on vol 1. The black wire from the bridge pickup and the white wire from the neck pickup are attached to poles on
20210223_123312.jpg
vol 2.
 
#211
Larry Balara said:
I have attached a picture of the control cavity. The pickups are wired black wire from the neck pickup to the top of vol 1 and white wire from the bridge pickup to a pole on vol 1. The black wire from the bridge pickup and the white wire from the neck pickup are attached to poles on View attachment 4180704 vol 2.
Click to expand...
Yeah so there would be no way for the HRI to function the way it was intended without rewiring the Series/Parallel switch to match the diagram you posted (your bass is currently just wired for a typical series/parallel connection). The HRI coils are actually run in series with both pickups (picture them like extra turns of wire at the start of each pickup, but without magnets they are only picking up noise interference which is run out of phase with the pickup it is attached to- basically like a humbucker pickup without magnets on one of the coils), and they actually are still in the circuit when the bass is in series mode (there are just two of them out of phase with each-other so the effect is still noise-free operation). Pretty cool scheme IMO- I want to try one! Any coil like that in series with the pickups will change the tone somewhat, so curious how noticeable it is.
 
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#213
Larry Balara said:
But is it only the pickup wires I need to change? It seems this is what the difference is!
Click to expand...
Yep, basically rewiring the Series-parallel switch to match the diagram you posted with both your pickup ground connections and the two seperate wires from the HRI and also make sure to ground the black wire from the HRI. I'm not sure what the purpose of the orange wire from the HRI is, but it looks like it may be going to a power connection on the preamp board which is interesting- that's really the only head-scratcher here (maybe the HRI is an active device?). Maybe Xotic can give you a clue on this. Everything else in your wiring should work the same.
 
#217
oakley86 said:
Thanks for the great post. I have maybe a dumb question, but if all the metal parts are grounded then
what is purpose of the shielding. My bass is an original 1951 p-bass with only a hole that carries the wiring from the pickup to the pots
Click to expand...
Basically, the electronic bits inside your bass may, under certain conditions, act as an antenna for various unwanted noise. Such unwanted noise then gets introduced to your amp as part of the bass signal. Shielding acts as an antenna to intercept all that noise and shunt it to ground before it can get to the signal-relevant parts.
 
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#219
Some (hopefully) helpful tips:

Remember to shield the back of the pickguard cover. When you shield the control cavity, make sure the copper spills over the top a little bit so it makes contact with the copper on the back of the pickguard.

If in doubt, it's better to use too much than too little.

You can solder the bridge ground wire directly to the shielding. You can also solder the seams of the tape when you lay it down. This isn't necessary if the copper tape has conductive adhesive, but soldering has two benefits -- absolutely guaranteeing the conductivity of the shielding across all seams, and maintaining the shape and position of the tape in case the adhesive ever "dries out." (I have never seen that happen, but some people say it does.) What I did was solder everything, and then covered it with another layer of copper tape just to look pretty.

Most P basses have a single route for the pickup, wires, and controls, which is very easy to shield. But you said "hole." If your pickup route and control cavity are two separate routes connected by a drilled tunnel for the wires like a J bridge pickup, then if you choose to shield the pickup hole, make sure the pickup route shield and the control cavity shield are connected! (Some people caution against shielding the pickup area(s), saying the shielding can bleed off high end or otherwise interfere with the pickup. I have never experienced any kind of adverse effect on my basses with shielded pickup routes.)
66020.jpg
 
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