A question about Ohms - no, it's not what you think

[Danzilla]

I'm not asking about ohms in speakers, be it in series or parallel.

I'm talking in pickups.

What part do the ohms play in the pickup? Being units of resistance, I would think that a higher ohmage would have less output than a lower ohmage. Am I right?

And how does this effect tone? Looking at Carvin's website, (as I'm considering putting in a set of their pickups in my Schecter T5) They have bassicaly four types of J pickups:

 

J99: This J style single coil pickup offers deep bass, punch and extended clarity. 9.31K ohms

J99A: This single coil bass pickup has exceptionally wide tonal range with a full bell tone and a nice extended top end thanks to its Alnico V magnet. 8.29K ohms

H50A: This stacked humbucking bass pickup has exceptionally wide tonal range with a full bell tone and a nice extended top end thanks to its Alnico V magnet. 16.42K Ohms

H50 S: This stacked humbucking bass pickup has exceptionally wide tonal range with a full bell tone and a nice extended top end. 18.2K ohms

 

So the stacked humbuckers have 2 coils, and twice the ohms. Wait - I thought you divided ohms when you combined them...

 

Seeing as almost all of these pickups give a "full bell tone and nice extended top", do the ohms really matter? Is the magnet type (Alnico V vs...?) more of a factor?

Which ones will have more output, or will they be so close it won't matter?

Lay the science and the experience on me, brother bassers. And sisters, too.

[jcadmus]

I can't speak to the science, but it sounds like copywriter got lazy if everything has a "full bell tone and nice extended top."

 

I'll add that I had the H50N (stacked humbucker) pickups in my Carvins and they were very quiet -- as in sounded good and not noisy, not low output.

 

[WCriley]

Resistance and/or impedence numbers don't tell you much about the output or sound of a pickup. There are a lot of other design factors that come into play

 

But generally speaking:

 

Higher DC resistance usually means more turns of wire in the coil(s). This usually means higher output.

 

The trade off is that more turns of wire means more of the coil is further from the magnet/pole pieces. This usually means less high freq content in the output.

 

This trade off (strength vs. response) can be overcome with smaller diameter wire or stronger magnets...which then leads to more trade offs...aand on it goes.

[MoodyBluesKeys]

The stacked humbuckers two coils are wired in series, not in parallel. That is why their resistance (technically impedance, which is the AC property similar to DC resistance) increases rather than decreases.

 

The trick with humbuckers is that one winding is affected by the strings, the other winding is not affected by the strings - BOTH windings are affected by any hum from other electrical devices, and the windings are phased so that the hum pickup on one coil gets (mostly) cancelled out by the hum pickup on the other coil.

 

WCriley answered the other parts of the equation. Back in the old days of tube amps, most amps had a very high impedance input, but some of the early solid-state amps had a quite low input impedance. Most bass amps today have a medium to high impedance for the passive input, and a somewhat lower impedance for any active input. There is usually not much difference from a player's perspective unless one is using very long cabling between the bass and amp (like running a bass into a DI then to a mixing board several hundred feet away - the DI not only provides isolation, it also provides a balanced low impedance feed, which picks up less hum and noise).

 

[WCriley]

The trick with humbuckers is that one winding is affected by the strings, the other winding is not affected by the strings

I believe this is only true if the pickup employs a dummy coil. In typical humbuckers the coils are magmetically out of phase, and are then connected electrically out phase. The result is that while of the most "hum" is canncelled, the current generated by the strings in each coil is added together.

 

Most bass amps today have a medium to high impedance for the passive input, and a somewhat lower impedance for any active input.

Intersting. I always thought the active input (or switch on some amps) just padded down the signal from a poorly designed onboard preamp to prevent it from overloading the first stages of the amp. But I guess that in the process it could lower the imput impedence.

[MoodyBluesKeys]

The method of out of phase magnetics is also used in humbuckers, probably more so now than in the early pickups. Active inputs are handled differently by different amps, it is quite possible that some of the amps only pad down the signal, in fact probable if there is only a switch instead of two different inputs. My Trace amps do use different front end electronics which have different gains and different impedances.

[WCriley]

Reverse magnetic polarity has been used since the mid 50s when Seth Lover designed the first commercially available humbucking pickup for Gibson. To the best of my knowledge, every humbucking pickup designed since then has used the same principle.

 

An exception might be pickups that use a dummy coil to cancel hum. (Dummy coils don't have magnets.) I have no experience with dummy coils, but I'd think the coils would need to be far enough apart that the inactive coil isn't affected by the magnetic field surrounding the active coil. I'd be inclined to call that a humbucking "system" rather than a humbucking "pickup".

[itu]

Higher DC resistance usually means more turns of wire in the coil(s). This usually means higher output.

 

The trade off is that more turns of wire means more of the coil is further from the magnet/pole pieces. This usually means less high freq content in the output.

Actually, the inductance is affected if there are more or less turns. It has a lot to do with the sound.

 

http://en.wikipedia.org/wiki/Coil

http://info.ee.surrey.ac.uk/Workshop/advice/coils/

http://www.66pacific.com/calculators/coil_calc.aspx

 

By the way, probably the most known bass maker that uses dummy coil with single coil pickups is Alembic (http://www.alembic.com/prod/seriesii.html).

[rumpelstiltskin.]

it's both. the DCR and the inductance increase with more turns. the wire gauge used also has effects on both. (smaller wire has higher resistance and provides for higher inductance, but it can handle less current.)

 

impedance is a complex electrical characteristic expressed in Ohms, and it is the combination of resistance (also expressed in Ohms) and reactance (capacitance in Farads or inductance in Henries). true story: impedance is literally a complex expression, meaning it contains both real and imaginary numbers.

 

in the case of pickups, we're actually describing the DCR, and not the true impedance, when listing an Ohm measurement because of this:

 

Higher DC resistance usually means more turns of wire in the coil(s). This usually means higher output.

 

the actual inductance isn't particularly important except as it affects the resonant peak of the pickup's frequency response.

 

robb.