Extra 'Dummy Coil/Pickup' in a Jazz Bass with two Single Coil Pickups?

[Peter Weil]

Hi all,

I have been wondering for a while why manufacturers/luthiers do not offer the use of an extra 'dummy' coil/pickup in the typical 2 x single-coil jazz bass setup.

I have seen (but never heard, or played with) precisely two basses where this was done - one was a Status/Trace Elliot T-Bass - and I have always thought it was a neat idea.

The bass is set up with 3 pickups, two being the usual single coils and the third being a 'dummy' with no volume control, but still wired into the circuit.

Check out a link to an old review to get a flavour of what I mean: http://www.statii.com/status_cats/reviews/12/index.html

So...with this, you can, therefore, keep the 'dummy pickup' on all the time, allowing the bass to be humbucking even if one of the single coil pickups is fully turned down. This apparently then allows the classic single coil tone without the usual hum after one of the single coils is turned down.

I'm wondering about using this idea in a future custom/self-build, and I just wondered what others though/how I might go about it.

Pete

[fretlessman71]

Alembic also did this with great success. No reason why it shouldn't work.

[Webtroll]

I imagine cost restrictions come into play here. If I recall the dummy pickup on the Alembic basses is visible, but there's no reason it couldn't be stashed underneath a pickguard (no?).

[SGD Lutherie]

Alembics are active basses. It's hard to use a passive dummy coil without altering the tone of the passive pickups.

The newer Alembic pickups are stacked coils, with the dummy under the string sensing coil.

The problem with stacked pickups is the bottom coil cancels out a lot of low end when it's sensing the strings, or dulls the tone if it's a dummy.

It can be done, but they never sound exactly like single coils.

If you make the Jazz active, then it would be fairly simple to copy the Series II Alembic system. The early Alembics had the dummy coil inside the control cavity.

[Peter Weil]

Originally Posted by SGD Lutherie

Alembics are active basses. It's hard to use a passive dummy coil without altering the tone of the passive pickups.

The newer Alembic pickups are stacked coils, with the dummy under the string sensing coil.

The problem with stacked pickups is the bottom coil cancels out a lot of low end when it's sensing the strings, or dulls the tone if it's a dummy.

It can be done, but they never sound exactly like single coils.

If you make the Jazz active, then it would be fairly simple to copy the Series II Alembic system. The early Alembics had the dummy coil inside the control cavity.

Ahh. Thanks for the insight. I was hoping to keep the system all-passive; I'm not much of a fan of active pickups, although I have heard some nice on-board active EQ's.

Could I use my favourite passive pickups and maintain much the same single coil tone with a dummy coil as long as the circuit was active overall? Or are active pickups inherently different in some way to my favourite passive Aeros?

[SGD Lutherie]

With the right circuit you could use two single coils with a dummy hum canceling coil while maintaining the tone of the single coils, though passive pickups sounds a bit different when buffered.

I don't think anyone makes such a system as a third party retrofit, though it wouldn't be hard to do.

Active pickups are basically* passive pickups with some type of buffering and maybe tone shaping circuit inside the pickup, or in the case of Alembic, and some low Z pickups I was making, the circuitry could be outside of the pickup.

If you want a total passive setup, stacked hum-canceling are probably the best way to go, or the split coil pickups.



(*there are a few variations, such as low Z coils, or high Z coils feeding a differential input as with EMG's)

[Peter Weil]

Originally Posted by SGD Lutherie

With the right circuit you could use two single coils with a dummy hum canceling coil while maintaining the tone of the single coils, though passive pickups sounds a bit different when buffered.

I don't think anyone makes such a system as a third party retrofit, though it wouldn't be hard to do.

Active pickups are basically* passive pickups with some type of buffering and maybe tone shaping circuit inside the pickup, or in the case of Alembic, and some low Z pickups I was making, the circuitry could be outside of the pickup.

If you want a total passive setup, stacked hum-canceling are probably the best way to go, or the split coil pickups.



(*there are a few variations, such as low Z coils, or high Z coils feeding a differential input as with EMG's)

I'll keep it in mind, but it sounds like I should just stick to the tried-and-true single coils I've got, and just live with any noise.

[jacbass]

But what about a side-by-side humbucking pickup in which one of the coils contains magnet while the other does not. Will it still retain that single coil sound/tone while in humbucking mode? I also discovered that half of the dummy coil close to the pickup is being magnetised by the magnet in the main coil and by this, will the magnetised coil pick up string vibrations? My bass is passive and i was very disappointed to discover that my pickup werent full humbuckers as i thought they were so buyers beware of this scope.

[rojo412]

I was just about to ask about this topic...

Let's say you had a J bass that had 60 cycle hum. And you wanted to wire in a dummy coil to balance that out...

1) Would it work?
2) What kind of dummy coil do you need? Would any pickup work?
3)How do you wire it into the controls or the circuit in general?

[SGD Lutherie]

Originally Posted by rojo412

I was just about to ask about this topic...

Let's say you had a J bass that had 60 cycle hum. And you wanted to wire in a dummy coil to balance that out...

1) Would it work?
2) What kind of dummy coil do you need? Would any pickup work?
3)How do you wire it into the controls or the circuit in general?

It will work, but it will alter the tone of the pickups. This is because the dummy coil is usually wired in series, so the inductance changes.

But all you would need is another Jazz pickup with no magnets. It would work better if the poles were replaced with steel rods.

The best way to get a dummy coil system to work is with an active preamp to mix the dummy in with the passive pickups. This is the way the Alembic Series I basses worked.

The easiest solution is to get hum canceling pickups. If they are lacking any sparkle on the top end, you wont hear it in a band or recording context.

[line6man]

The problem with adding in a dummy coil to a two-pickup setup would be that it will only humcancel with the coil that is RWRP from it.

[narud]

Originally Posted by line6man

The problem with adding in a dummy coil to a two-pickup setup would be that it will only humcancel with the coil that is RWRP from it.

you make both pickups the same direction in a system like this though.

[narud]

Originally Posted by SGD Lutherie

Alembics are active basses. It's hard to use a passive dummy coil without altering the tone of the passive pickups.

The newer Alembic pickups are stacked coils, with the dummy under the string sensing coil.

The problem with stacked pickups is the bottom coil cancels out a lot of low end when it's sensing the strings, or dulls the tone if it's a dummy.

It can be done, but they never sound exactly like single coils.

If you make the Jazz active, then it would be fairly simple to copy the Series II Alembic system. The early Alembics had the dummy coil inside the control cavity.

what about john suhr's strat system? thats still passive right? scott henderson seems to be pretty happy with it and he's probably a bigger tone geek than the majority of bass players.

[line6man]

Originally Posted by narud

you make both pickups the same direction in a system like this though.

Well then they won't humcancel together, and that's apparently the most popular Jazz bass pickup setting.

[rojo412]

I asked because I was imagining using one of these strat pickups I have lying around and just tossing that in a control cavity...
But yeah, if I'm gonna go FAR, I'm just going to buy better pickups.

[narud]

Originally Posted by line6man

Well then they won't humcancel together, and that's apparently the most popular Jazz bass pickup setting.

you make the the 2 jazz pickups the same direction and the dummy coil rwrp. thats how john suhr has his strat system. all 3 pickups are the same direction/polarity and the dummy coil is reverse.

[SGD Lutherie]

Originally Posted by narud

what about john suhr's strat system? thats still passive right? scott henderson seems to be pretty happy with it and he's probably a bigger tone geek than the majority of bass players.

Yes, it's passive and uses a large area low resistance dummy coil.

You can certainly try something like that. How that would implemented on a Jazz bass is another question.

I've been thinking about doing an Alembic type system for Jazz basses, but it would probably require routing the bass.

But wait for my Jazz Sidewinders... they should sound just like single coils... high end sparkle and all.

[line6man]

Originally Posted by narud

you make the the 2 jazz pickups the same direction and the dummy coil rwrp. thats how john suhr has his strat system. all 3 pickups are the same direction/polarity and the dummy coil is reverse.

Yes, but the two Jazz pickups will not humcancel together, they will only humcancel soloed with the dummy coil.

If you put both pickups on full, which is the most common setting for most Jazz bass players, the bass will not humcancel, with or without the dummy coil.

[SGD Lutherie]

The problem is that with a Strat, and something like the Suhr system, you don't blend the pickups. They are on or off. So the dummy coil only has to work with individual pickups. The 2 and 4 positions will already hum cancel.

With a Jazz bass you have blending going on, so you need to humcancel each pickup before they are blended.

[narud]

Originally Posted by SGD Lutherie

The problem is that with a Strat, and something like the Suhr system, you don't blend the pickups. They are on or off. So the dummy coil only has to work with individual pickups. The 2 and 4 positions will already hum cancel.

With a Jazz bass you have blending going on, so you need to humcancel each pickup before they are blended.

positions 2 and 4 wouldnt already humcancel though because you have to replace the middle pickup with one that isnt rwrp in the suhr system.