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Alnico 5 bad hum in Dimarzio FRED pickup


ry1633
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Hey all,

 

I'm new here and I need some help troubleshooting a weird and annoying hum in my rig. I have a Warmoth homemade Strat that I've used for years. It originally had a Dimarzio Virtual Solo in the bridge but I wanted something fatter so I switched it to a new Dimarzio FRED which is my favorite HB of theirs. But the FRED hummed a LOT when I played so I checked the wiring and even had two techs check it out and Dimarzio did also. They couldn't find anything wrong. But to me the hum was really bad - just like a stock single coil. I even had Dimarzio build me a brand-new FRED from scratch and I still think it hums too much. So this is the layout:

  • Bridge: Dimarzio FRED (<--THIS is the PU giving me the hum problems, worse than a stock single coil IMO)
    Middle: Dimarzio Heavy Blues 2 (perfectly quiet)
    Neck: Dimarzio HS3 (quiet and just fine)

 

When I kick on my crunch boxes the hum from the FRED gets really bad. I have to really dial in my noise gate to kill it, and it obviously hurts the sustain if I use the gate too much. But if I don't use the gate then the hum is really bad. Here's my board in order of signal path:

  • Line 6 G50 Wireless
    Boss TU-3 Tuner
    Crybaby Wah
    MXR Phase 90
    Barber Direct Drive custom
    Barber Dirty Bomb
    Xotic EP Booster
    ISP Decimator II
    BOSS DD6 Delay
    BOSS CH-1 Chorus

 

I've had brand new pots, switching and wiring put in too. Double checked the circuit with my tech and we're sure it's right compared to the diagram for the FRED and similar Dimarzio units. I'm at a loss and really could use some advice. Maybe the output hum of the Alnico 5 magnet is something I have to live with?

 

Ideally, I'd really want the EVH / Gary Moore "Brown Sound" in a pickup, and I'd like to be as quiet as possible. Maybe I should try a ceramic magnet pickup? Dimarzio has actually suggested I try their Illuminator (neck) model in the bridge.

 

-ryan

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I can try to post a clip. All of my gear is at my drummers house right now, where I don't have good access to anything to record it with. For comparison's sake, I have a different guitar with a Fast Track 2 in it, and through the same amp/pedal rig it hums a little bit, but not nearly as bad as my guitar with the FRED in it. And the Fast Track 2 technically is a hotter pickup than the Fred.

 

To me this almost sounds like a ground problem? When I kick either of my crunch boxes on with the FRED humbucker selected, it hums just about as bad as a old stock single coil. The hum easily overtakes the natural sustain of notes and chords after 3-4 seconds. I have to use my ISP Decimator to dial it back, and I have it dialed back so hard that it really chops the notes off in an unnatural way.

 

Is there anything I can look at with the wiring? This is the second Fred that I've went through with the same problem, I can't believe that two in a row would be bad?

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It HAS to be a ground issue.. make sure the bare wire is properly wired to the back of one of the pots

 

I would say it is most likely a ground issue. However, if that model pickup has a lower LF extension, it could be that a stomp box downstream has an issue with the additional LF. The problem would be latent or minimal when playing the other single coil pickups, especially if they have a limited LF range. The OP should start troubleshooting in a logical and linear method as I started to describe in my previous post. Start with the guitar plugged right into the amp and add the stomp boxes one at a time.

 

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I'll check it out. Dimarzio sent me three different wiring diagrams. I really notice the hum when I go to the crunch boxes in my rig - either the Barber Dirty Bomb or Direct Drive.

 

But I have a Dimarzio Heavy Blues 2 in the middle position - and even with the crunch boxes on, that pickup is dead quiet. Switch over to the Fred humbucker, and it hums as bad as any standard single coil I've ever owned.

 

But... this is a brand-new FRED that Dimarzio custom-built for me after I send it in the first one I bought a month or two ago. So I doubt that it would be the pickup's fault after all this. I just wonder if my tech didn't do something right with the wiring?

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I would say it is most likely a ground issue. However, if that model pickup has a lower LF extension, it could be that a stomp box downstream has an issue with the additional LF. The problem would be latent or minimal when playing the other single coil pickups, especially if they have a limited LF range. The OP should start troubleshooting in a logical and linear method as I started to describe in my previous post. Start with the guitar plugged right into the amp and add the stomp boxes one at a time.

 

Also what do you mean by LF extension?

Edited by ry1633
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My experience is that regarding noise suppression, all humbuckers are not created equally. I had a JB in the bridge of a Hamer USA Mirage II that seemed a little too harsh on that guitar. After some contemplating and discussion on here, I decided to try the Dimarzio Breed F Spaced neck pickup that a forumite suggested. Well to make a long story short, I like the pickup fine, and it is not harsh like the JB in that guitar, however, it is not nearly as quiet as the Seymour Duncan 59 that I have in the neck slot. I have to watch how close I'm playing in front of an amp or florescent lights only with that humbucker.

Edited by wankdeplank
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Maybe shielding the body may help. Be sure your bridge ground wire is connected too. Its an easy thing to miss when resold ring pickups. I've had many break away from the bridge of tail as well.

 

As a quick test you can also run a ground wire to the pickup casing. Just to see if the ground was lost there. Also be sure the bare hot wires used to connect it to the switch or pots are short. Peeling back the ground shield wire leaves the hot wires exposed to ac hum.

 

This pickup does have a mid hump designed to it. Your outer pickups may have a valley in its response where those AC hum frequencies reside so they block and cancel the hum better.

 

The other static test you can do is measure the two coils of the humbucker with an ohm meter. The coil resistances should be identical in most humbuckers. The coils being equal and opposite are what buck the hum. If the coils are uneven, they may give you a unique tone, but thay wornt buck the hum as well.

 

Also note, the shield cround should be connected to signal ground. If for some reason you connected the shiled to the pots only, that might be the cause of your problem. Signal ground and shield ground need to go to the same connections.

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Thanks everyone. I'm taking it back into the shop tomorrow. I played it at band practice tonight, and all the guys agreed they thought something was wrong with it. The hum on the new pickup was that bad. I'll keep everyone posted. I had Dimarzio send me some diagrams to double check things.

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An uncovered humbucker will have some tendency to pickup hum compared to a covered humbucker.

 

Any humbucker design with unequally wound coils will have more hum.

 

Pickups with weaker magnets (such as AlNiCo II) *can* be more susceptible to hum than pickups with stronger magnets (such as ceramic / ferrite).

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Strength of magnetism has zero to do with hum. Coil core permeability and coil inductive balance are the key items.

The coils will buck the hum even if they are air core but they would not produce a signal from the strings without the strings cutting through a magnetic field.

 

Pickups are designed with a Ferris/nickel core. This core has a dual purpose. It increases the coils inductance in Henries and it focuses the magnetic field on the strings themselves.

 

Two air coils of equal with opposite winds should phase cancel the hum entirely in a perfect world. When you add iron to the cores, you change the strength of the two coils. Its doesn't matter if the cores are magnetic or not, it matters that the cores have an equal amount of ferric content. If the iron in one core is purer then the other, then this would cause an imbalance. If the core is larger and fits tighter in one then the other, then it will provide better inductance. If one core is drilled for adjustment screws, and those screws have less ferric content, again, this can cause a difference in permeability, changing the inductance of the two coils.

 

The only thing magnetic strength does is change the number/density of magnetic lines of force the strings cut through and thereby changes the strength of the signal generated in the coils.

 

The misconception is the AC radio waves which produce the hum are attracted to the pickups because they are magnetic. This is not the case. The winds and wiring act like an antenna and as the AC waves pass through the air and cut through the wires, they generate eddy currents in the wire. When the eddy current in one coil are equal and opposite to the other coils they theoretically cancel out.

 

What a weaker magnetic field may do is decrease the pickups output. In order to get that pickup louder, you increase the amplifier gain and any remaining EMF that's not being canceled out would likely be amplified just that much more. So its not the magnet strength that increases/decreases the strength of the AC hum. Its the amount of gain used to amplify the signal that can increase the noise floor and make the hum be heard. A strong output pickup would more likely have the gain dialed back which also lowers the noise floor.

 

 

These pickups are high impedance so I suspect they are high output. They also have a double row of screws so I suspect the Ferris Cores are balanced. The coil winds being balanced and how tightly they fit around the cores are all that's left.

 

My guess is the OP has a wiring issue he has not realized yet. Every manufacturer uses different color codes and diagrams have to be properly deciphered. These pickups may be wired in parallel instead of series or he didn't know shield ground is a 5th connection, 4 wire diagrams often ignore completely. This 5th wire shields the two sets of coil wires and is likely soldered to the Pickup can via the pickup base. It carries no pickup signal, it merely acts as a faraday cage.

 

My bet is, The braded shielding is either not connected at all or its connected to the center or hot wires. Most 2 & 3 wire wiring pictorials have a common shield ground to signal ground. 4 wire conductors have a 5th independent shield wire. This allows you to use different series, parallel, reverse and split coil combinations while keeping the shield separate so it can shield coils themselves and not be reversed when the electrical signals are reversed or disconnected. If its floating or connected to a hot wire the hum can be terrible.

 

When the shield floats, instead of carrying the hum to ground before it gets to the core wires, it does just the opposite and surrounds the wires and induces hum from a 360 degree radius. The two coils do create a loop so there is a normal signal. Its just there's so much EMF being induced, by the floating shield it winds up be double what you'd hear from any unshielded single coil pickup.

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I took my guitar and pedalboard into my local music shop - and my tech said he wired it up just like the diagram that Dimarzio sent me. He knows that Dimarzio pickups have the same wire colors as Duncans and other vendors, but they don't mean the same things necessarily. I plugged my rig into to a new Fender Blues Deluxe amp there which is what I have. The hum was still there much quieter and not as pronounced as in my drummer's house for band practice. My tech already grounded it correctly on the bridge claw and everything. So he stands by his work, and my rig was indeed quieter at the store.

 

I have a Barber Dirty Bomb and Direct Drive - which are very powerful crunch boxes and tend to magnify everything they touch, even the bad noises LOL

 

The only thing I can conclude is that the hum is magnified by the house wiring at my drummers house. There are several new florescent lights in his basement, because he had his basement (our practice space) redone from a flood a few years ago. I haven't gigged with the guitar yet, that's coming in a few weeks.

Edited by ry1633
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