New hum cancelling widget: Xotic HRI

[Kindly Killer]

"To me it actually gives it more body."
Interview with John Peña "Xotic Bass HRI (Hum Reduction Inductor)" - YouTube

What is it?

there is an image of it here: Interview with John Peña "Xotic Bass HRI (Hum Reduction Inductor)" - YouTube

[David King]

Dummy coil.

[big_teee]

Dummy coil.

That is interesting, is it just a Air Coil, or would it have magnets in it?
Also would it be in series or parallel?
T

[David King]

Great question Terry.
They could have loaded it with unmagnetized alnico slugs but I'm not sure what that would accomplish, dummy coils are usually aircoils. As long as the area*turns is the same as each pickup it should work just fine. What I'm curious about is how do they gradually dial it in as the balance knob is rolled away from the center detent. They also have to flip the wind direction as they go from neck to bridge PU since presumably the pickups are humbucking as a pair and would be RPRW.

I doubt series /parallel makes much difference in the tone but I'm guessing they chose parallel.

[Stealth]

David, I think the un-magnetized alnico slugs are in there to boost the coil inductance simply by providing ferromagnetic material inside - they could've probably done the same thing using regular soft iron slugs, but this way the inductance probably came closer to the "proper", magnet-loaded coil.

[Mike Sulzer]

Great question Terry.
They could have loaded it with unmagnetized alnico slugs but I'm not sure what that would accomplish, dummy coils are usually aircoils. As long as the area*turns is the same as each pickup it should work just fine. What I'm curious about is how do they gradually dial it in as the balance knob is rolled away from the center detent. They also have to flip the wind direction as they go from neck to bridge PU since presumably the pickups are humbucking as a pair and would be RPRW.

I doubt series /parallel makes much difference in the tone but I'm guessing they chose parallel.

It is not just area*turns; magnetic material with permeability counts too. You would want to make the core as much like that of the pickup as possible. The increase in sensitivity from material with permeability is not huge with short open cores, but it is enough to matter with a dummy coil, and if you use a different kind of core, it can be difficult to get the correct sensitivity.

Parallel would cut the pickup voltage, and so I suspect that it is series.

[big_teee]

It is not just area*turns; magnetic material with permeability counts too. You would want to make the core as much like that of the pickup as possible. The increase in sensitivity from material with permeability is not huge with short open cores, but it is enough to matter with a dummy coil, and if you use a different kind of core, it can be difficult to get the correct sensitivity.

Parallel would cut the pickup voltage, and so I suspect that it is series.

Mike:
If it is in Series, Series with what.
The Bass Has 2 Pickups with a balance blender.
The 2 pickups with the widget out of the circuit, were Hum canceling, so one coil must be RWRP.
So how did he mix the widget with the 2 Pickups.
Please buy one and reverse engineer it for us!
B_T

[Mike Sulzer]

Mike:
If it is in Series, Series with what.
The Bass Has 2 Pickups with a balance blender.
The 2 pickups with the widget out of the circuit, were Hum canceling, so one coil must be RWRP.
So how did he mix the widget with the 2 Pickups.
Please buy one and reverse engineer it for us!
B_T

I think it has two coils, one for each pickup. The special switch used on the video would have to be double pole, but that is no problem.

(I like that statement that it has no effect on the tone, but nonetheless gives it more body.)

[big_teee]

I think it has two coils, one for each pickup. The special switch used on the video would have to be double pole, but that is no problem.

(I like that statement that it has no effect on the tone, but nonetheless gives it more body.)

The more body Line, reminds me of the old Joke.
"The three greatest Lies."
Joke not suitable for Forums!
Maybe You know it!
T

[Mike Sulzer]

The more body Line, reminds me of the old Joke.
"The three greatest Lies."
Joke not suitable for Forums!
Maybe You know it!
T

That joke has many versions, and I know the one you mean.

[big_teee]

I would like to make one, if it could be mounted to the side like that!
Where do we start?
B_T

[David King]

I thought I read here a long time ago now that the permeability of Alnico was close to that of air??
I'm not convinced that two coils are needed. I'm thinking the ends of the dummy coil could be attached to the far ends of the blend pots so that as you dialed further away in either direction from both pickups on full in the center detent position you would gradually add in just the right amount of the dummy coil in the correct phase. I'd have to build one to try it.

Terry just wind a 3rd coil, tapped in the center but identical to the 2 PU coils but twice as many turns total (or bifilar) and load it with un-magnetized Alnico slugs (if necessary). Use a dual ganged blend pot and connect the ends of the coil to the Hot sides of both pots where there would normally be a jumper. Your center tap would go to output. It might just work...

[big_teee]

I thought I read here a long time ago now that the permeability of Alnico was close to that of air??
I'm not convinced that two coils are needed. I'm thinking the ends of the dummy coil could be attached to the far ends of the blend pots so that as you dialed further away in either direction from both pickups on full in the center detent position you would gradually add in just the right amount of the dummy coil in the correct phase. I'd have to build one to try it.

Terry just wind a 3rd coil, tapped in the center but identical to the 2 PU coils but twice as many turns total (or bifilar) and load it with un-magnetized Alnico slugs (if necessary). Use a dual ganged blend pot and connect the ends of the coil to the Hot sides of both pots where there would normally be a jumper. Your center tap would go to output. It might just work...

Thanks David:
Having trouble visualizing the wiring of the dual pot.
Sounds like a neat concept.
T

[Mike Sulzer]

I thought I read here a long time ago now that the permeability of Alnico was close to that of air??
I'm not convinced that two coils are needed. I'm thinking the ends of the dummy coil could be attached to the far ends of the blend pots so that as you dialed further away in either direction from both pickups on full in the center detent position you would gradually add in just the right amount of the dummy coil in the correct phase. I'd have to build one to try it.

Terry just wind a 3rd coil, tapped in the center but identical to the 2 PU coils but twice as many turns total (or bifilar) and load it with un-magnetized Alnico slugs (if necessary). Use a dual ganged blend pot and connect the ends of the coil to the Hot sides of both pots where there would normally be a jumper. Your center tap would go to output. It might just work...

I think the permeability of Alnico is a few times air, that is, low compared to steel, but enough to matter in achieving balance.

I am thinking of two windings rather than two completely separate coils as I believe your are.

But the key thing in order to avoid affect on the sound is low inductance. The typical approach is a large air coil coil with many fewer turns than a pickup (Suhr): low inductance, but similar sensitivity to hum as the pickup. But that is not what they are doing here. Another approach might be a larger magnetic core than extends as nearly as possible through the entire thickness of the bass and has as big a diameter as you can fit in. Maybe that is what they are doing. I did not see anything about electronics, so this is passive?

[David Schwab]

I take it that they haven't applied for a patent? That would clear up some details.