Both Volume pots for series

[ChristoMephisto]

About to wire up an Aria JBass from the early 70's with Fender Original Jazz Bass pups and thinking of adding a push/pull pot for series /parallel.
Instead of wiring the bridge pup to the switch, it'd be wired to the pot then the switch. Done this years ago on a LP using the Jimmy Page style wiring and remember series sounded better when the first pup is backed off a bit.
The pickups are suppose to cancel out some frequencies because they're rprw when in parallel, would the same happen when in series too?

 

[tstone]

Being RWRP does not cause the pickups to "cancel out some frequencies." It causes the combined pickups to be humbucking -- i.e., to reject electromagnetic interference -- when both are selected and both are at the same volume level. That will be true whether they are connected in series or in parallel.

 

[line6man]

About to wire up an Aria JBass from the early 70's with Fender Original Jazz Bass pups and thinking of adding a push/pull pot for series /parallel.
Instead of wiring the bridge pup to the switch, it'd be wired to the pot then the switch. Done this years ago on a LP using the Jimmy Page style wiring and remember series sounded better when the first pup is backed off a bit.
The pickups are suppose to cancel out some frequencies because they're rprw when in parallel, would the same happen when in series too?

How exactly do you plan to do that?

If you run the bridge pickup into a standard volume pot setup, then to the switch, when you put the pickups in series, the volume pot will place a rather high impedance between the neck pickup's negative phase lead and ground, and as the pot is adjusted, it will "sweep" the bridge pickup's hot between the neck pickup's negative phase lead and ground. This means that as the pot is rolled down, the overall volume will decrease until the neck pickup is nearly silent, when the bridge pickup is out of the circuit.

RWRP means that the signals which were transduced from the movement of the strings remain in-phase, while any 60Hz hum is out-of-phase, such to allow destructive interference between waveforms that cancels the hum, while leaving the audible signal unaffected. You do not want your audible signals from each coil out-of-phase, as that yields a very thin and nasal tone, with most of the frequency content cancelled out. When two pickups are played together, however, there are slight phase differences between them, due to the fact that they sense the movement of the strings from different locations. These slight phase differences cause various constructive and destructive interferences that reinforce or cancel some frequencies, but only a little bit.

 

[ChristoMephisto]

The RWRP thing usually has me confused, but knew it's not the same as OoP. Being an old tele player, knew the OoP sound is a thin, nice sound with a guitar, but it's not something you want in a bass. Can't remember where i saw it, but Fender was saying the two pickups combined cancel out some frequencies.

The series wiring is the same concept as Jimmy's LP, or Borsanova's "Broadbucker"
http://guitarnuts2.proboards.com/index.cgi?board=schem&action=display&thread=3159

I've done this in the past on a tele, and it worked out well, rolling back the volume on the bridge doesn't shut off the series pups, just leaves you with the neck single coil. You would need to include the neck's volume pot's ground lug to the s/p switch along with the neck's ground.

 

[khutch]

The RWRP thing usually has me confused, but knew it's not the same as OoP. Being an old tele player, knew the OoP sound is a thin, nice sound with a guitar, but it's not something you want in a bass. Can't remember where i saw it, but Fender was saying the two pickups combined cancel out some frequencies.

Never heard the RWRP acronym before but I am guessing it stands for reverse wound, reverse polarity. It actually is the same thing as out of phase but it is more complex. Two coils reverse wound will produce out of phase 60 Hz hum components from stray 60 Hz magnetic fields and thus cancel them out when they are connected together. If you now put magnets in one of the coils you have a dual coil hum canceling pickup. The tone is affected by the inductance of the second coil but you do have a fully functional pickup and some of us are of the opinion that the tone is fine, just different from a single coil pickup. If you put the same magnetic structure in the second coil it will produce both hum signals and string signals that are out of phase with the other coil's and so both will cancel out if you combine them. If instead you reverse the magnetic polarity of the second coil the phase of its hum component will be unaffected (because it is due to magnetic coupling from an external source whose polarity has not changed) while the phase of the string signal will invert which means it will now match that of the first coil and you have a full humbucking pickup. So RWRP lets you combine the string signals in phase and the hum signals out of phase, the best of both worlds!

Two pickups at different locations along the length of the string will indeed cancel some harmonics of the string motion and perhaps completely when they are combined. The reason for this is that while the phase of the two coil signals are the same for string motions in the same direction, all the harmonics above the fundamental produce string motions that reverse directions as you move along the length of the string. The second harmonic has a motional null in the middle of the string and one half is moving in the opposite direction as the other. The third harmonic has two motional nulls and the two end sections move in the opposite direction as the middle. And so on for all the other harmonics. So for the higher order harmonics that have one or more motional nulls located between the two the signal from the neck and bridge pickups can be out of phase and they can cancel completely if the volumes of the two pickups are adjusted just right.

This is not frequency selectivity of electronic circuits in the normal sense, it is an electro-mechanical effect.

Here is a Mr. Science experiment you likely have already done. If you have ever played open string harmonics (and who among us has not?) you have taken advantage of the string motional nulls in another way. Place your finger lightly on a string right above the 12th fret and pluck it. The string will ring at the octave of the open note and you can hold your finger there without affecting the sustain very much because the string is not moving at all precisely above the 12th fret and hardly at all at any point across the width of your finger so almost no energy is lost to your finger. Move your finger towards the bridge (or in theory the nut but I have never done it that way) and you can excite other open string harmonics the same way. You can run into the same phenomenon in a perverse way when you try to mute an open string with light finger pressure. If you happen to mute a location that has a motional null for some harmonic you will mute all the string motion except that harmonic which will continue to ring, much to your disgust!

Ken

 

[ChristoMephisto]

The question of the rwrp pups was only a second thought kinda thing.
Still wondering about using two volume pots while in series.

 

[xaxxat]

This diagram shows how to wire for 2 independent volumes in a series circuit. Courtesy of walterw.

 

[SGD Lutherie]

The RWRP thing usually has me confused, but knew it's not the same as OoP. Being an old tele player, knew the OoP sound is a thin, nice sound with a guitar, but it's not something you want in a bass. Can't remember where i saw it, but Fender was saying the two pickups combined cancel out some frequencies.

The reason why the two coils are not out-of-phase if cause the magnetic polarity is also opposite, so that puts the signal from the strings back in phase, but cancels out hum, because the hum doesn't require the magnets to be picked up.

Out-of-phase pickups are cool on guitar, and pretty much useless for bass.

 

[SGD Lutherie]

Never heard the RWRP acronym before but I am guessing it stands for reverse wound, reverse polarity.

It's used for Fender guitars when talking about either the middle pickup on a Strat, or for a Tele. In those cases they actually wind one pickup in reverse. But of course humbuckers are usually wound the same way, and wired up out-of-phase.

 

[walterw]

right; you can really "reverse-wind" a pickup (which you should do with alnico-pole pickups so the ground end of the coil is still against the magnets) or you can "fake" it by just reversing the leads; as long as the magnets are reversed also, either way will cancel hum.

 

[SGD Lutherie]

right; you can really "reverse-wind" a pickup (which you should do with alnico-pole pickups so the ground end of the coil is still against the magnets) or you can "fake" it by just reversing the leads; as long as the magnets are reversed also, either way will cancel hum.

Yes, for alnico single coils you should have the ground at the start.