What resister will make series/parallel equal in volume

[JMDT]

On an L2X00.

 

[sunbeast]

Its not really that simple...there's no "series output" in the circuit that you could add resistance to- there are only 2 outputs from the series/parallel switch, one for each pickup. The easiest way to deal with it is just to find an approximate volume knob setting for the series that sounds balanced with parallel and turn down the volume when you switch to series (pretty much the same effect you get with the resistor, as a pot is simply a variable resistor). The only other possibility I could think of would be adding another switch or push/pull pot with an attached resistor, but then you'd still need to flip 2 switches when switching from series to parallel....

Karl

 

[Caimanson]

You could experiment with a potentiometer, inserting it on the series mode perhaps.
Once you get a similar volume between series/parallel measure the resistance of the pot and get the equivalent resistor, or fix a small potentiometer inside the circuit compartment.

 

[Chef]

I find that rolling bass off when switching to series can work as an effective volume control...

 

[francisl2500]

+1 i agree Chef
Francis

 

[JMDT]

Interesting concept, I'll have to try that and get back with you Chef.

 

[sunbeast]

You could experiment with a potentiometer, inserting it on the series mode perhaps.
Once you get a similar volume between series/parallel measure the resistance of the pot and get the equivalent resistor, or fix a small potentiometer inside the circuit compartment.

The problem with this is, as I said, there is no direct connection to "series mode". When a pickup is in series mode, one coil from the pickup is "sent through" the other coil- so the hot output of the series/parallel switch is either that single coil (in series mode) or both coils (in parallel mode). Adding a resistor to the output part of the switch would lower the volume of both modes. This would work on a single pickup bass (or a bass with seperate coil switches for each pickup)ch with a 4PDT switch (one part of the switch for the series parallel option and the other part to add resistance when the series was selected). The L2000 already uses a 4PDT switch as there are 2 pickups, and there are no 6PDT switches I'm aware of that would be compatible- so the only alternative is to add a seperate switch or find some other way, such as volume or bass rolloff.....

Karl

 

[Caimanson]

The problem with this is, as I said, there is no direct connection to "series mode". When a pickup is in series mode, one coil from the pickup is "sent through" the other coil- so the hot output of the series/parallel switch is either that single coil (in series mode) or both coils (in parallel mode). Adding a resistor to the output part of the switch would lower the volume of both modes. This would work on a single pickup bass (or a bass with seperate coil switches for each pickup)ch with a 4PDT switch (one part of the switch for the series parallel option and the other part to add resistance when the series was selected). The L2000 already uses a 4PDT switch as there are 2 pickups, and there are no 6PDT switches I'm aware of that would be compatible- so the only alternative is to add a seperate switch or find some other way, such as volume or bass rolloff.....

Karl

In a standard series parallel configuration (J type bass) it is perfectly possible to insert a resistor in series without affecting the parallel mode at all, using a single dpdt switch.
In the L2x00 you'll obviously need a separate resistor for each pickup.

I don't know how the coil switching is wired on a L2x00, so it may or may not be possible without further modification.

 

[sunbeast]

In a standard series parallel configuration (J type bass) it is perfectly possible to insert a resistor in series without affecting the parallel mode at all, using a single dpdt switch.
In the L2x00 you'll obviously need a separate resistor for each pickup.

I don't know how the coil switching is wired on a L2x00, so it may or may not be possible without further modification.

I disagree- can you provide a diagram for this?

Thanks,
Karl

 

[DavePlaysBass]

You can replace the shorting wire in series mode with a resistor. I corresponded with one guy (Benj) who used a 47k to get equal volume and 33k to get a slight boost from series. However, in doing this you will also effect the frequency response of things by quite a bit. It also is not clear to me exactly what impedance the 47k is working with to form a voltage divider. However, the guy I was talking with knew his stuff and I do not doubt his results. I just am not sure how well they extrapolate to everyone's situation.

Dave

 

[sunbeast]

Dave- are you talking about the wire that shorts the hot output of one coil through the ground of the other coil? wouldn't that put the 2 coils out of balance with each other (so they'd no longer be humbucking)?

I was actually just looking at the newer L2000 wiring diagram and stand corrected about the possibility of adding a resistor that would work only in series mode on a newer L2x00- however it wouldn't apply to a Jazz bass style series/parallel situation (ie- 2 pickups in series with each other vs. 2 coils of the same pickup), as that situation requires 2 outputs (one for each pickup) in parallel mode, where 2 coils for a single pickup (as in the G&L) only require 1 output in either mode. My L2000 (and my old L2500) is an early 80s one with "single coil with bass boost" in place of series, and the switch is wired in a way that the resistor would affect both series and parallel.

I'll try to post a little diagram to show where the resistor would go (and maybe someone can back me up as to whether or not its correct!- I'm kinda hopped up on caffeine at the moment...)

Karl

 

[sunbeast]

So, the series/parallel switch on an L2x00 is basically 2 of these on top of each other (one for each pickup). The colored lugs on the switch represent where pickup wires are connected, the grey ones are lugs not connected to the pickups, and the black line off the left side is a ground connection that should already be on your switch (hope that makes sense!). The Green Line would be the resistor and one would be attached across the bottom right and top left of each half of the switch.

This essentially works the same as rolling off the volume a little when in series...not sure what effect it might have on the sound- could dull it a little...

I can't help on the value- maybe try DavePlaysBass's suggestion of 47K, or Caimanson's method using a potentiometer (or measuring the change you make on the volume control) would also work...

Sorry I wrongly suggested this wasn't possible- as I said, my L2000 was wired differently than the current G&L diagram...

Karl

 

[DavePlaysBass]

Dave- are you talking about the wire that shorts the hot output of one coil through the ground of the other coil? wouldn't that put the 2 coils out of balance with each other (so they'd no longer be humbucking)?

Yes

Out of balance in series mode is when you have a parallel path to ground at the series point as defined above.

If you place a resistor between the two coils so it is in series (not parallel) it will not unbalance the coils. Both coils still have to flow all their current thru the resistor (think of the entire loop out and back).

However, adding this impedance will increase the effective source impedance of the overall pickup source and will roll off higher frequencies. In active mode it will see a 1000pF capacitor as a load along with the volume and tone loading. In passive it will see all that plus the cable capacitance.

Also, you can connect a series / parallel scheme to either a humbucker like a G&L MFD or two single coil jazz pickups. With the G&L MFDs you use two poloes on a 4PDT switch and with a jazz pickup pair you also use two poles on a DPDT. They are exactly the same wiring, except the coils are in different locations on the bass body.

 

[DavePlaysBass]

And to add, the series resistor thing was done with a bass that did not have the bass boost caps. These caps will definitely interact. I have some long winded thoughts on that if anyone is serious about the mod with the bass boost caps drop me a line.

 

[sunbeast]

Also, you can connect a series / parallel scheme to either a humbucker like a G&L MFD or two single coil jazz pickups. With the G&L MFDs you use two poloes on a 4PDT switch and with a jazz pickup pair you also use two poles on a DPDT. They are exactly the same wiring, except the coils are in different locations on the bass body.

The difference being that on a Jazz bass, there are generally 2 hot outputs that go to the 2 seperate volume pots when in parallel vs. the single pickup output on the G&L.

I'm still confused by the idea of putting the resistor between the 2 coils in the series setting vs. putting the resistor to ground at the end of the series chain, where the signals of both coils would hit it. The latter would be the same as running a series signal through a fixed volume pot, which shouldn't put the coils out of balance, but the former would put all the resistance on the grounded coil if I'm understanding correctly...

Karl

 

[DavePlaysBass]

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The above is balanced. Any voltage induced on the bottom pickup is cancelled by an out of phase voltage generated on the top pickup. If you throw in a parallel element (such as capacitor to ground or capacitor to jack) at the series shorting point, this is no longer true. Even if the two pickups generate out of phase noise voltages, they do not cancel each other out because of the unbalancing created by a parallel element at the series point.

You can replace the "neck volume" and "bridge volume" connections with the pickup selector switch in a G&L. If they are coils on the same humbucker, both the "neck volume" and "bridge volume" points go to say the neck select point. So the diagram above applies to any bass with two coils (jazz, humbucking pair, etc).

Here's a G&L schematic. If you pull the bass boost aps, you have essentially the same wiring diagram I show above. And you can replace the short with a resistor.

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[Caimanson]

I opened my L2500, the middle switch has 12 pins which would explain how the coil switching is done.

The strange thing is that the pickup selector has nine pins, so I assume that that it works in combination with the small pcb circuit

 

[DavePlaysBass]

I opened my L2500, the middle switch has 12 pins which would explain how the coil switching is done.

The strange thing is that the pickup selector has nine pins, so I assume that that it works in combination with the small pcb circuit

Sometimes they use what they have laying around. The minimum needs for the pickup selector is a SPDT (single pole, double throw).

I had a Climax that used a 2 postion 3PDT (9 pins) switch for the active / passive switch. I ened up replacing it with a 3 postion DPDT (6 pins) switch so I could wire it up like a L2K with passive / active / treble boost. The original switch must have been a cheap buy from somewhere because it waw overkill.

 

[sunbeast]

Cool! Thanks for the clarification, Dave!

Karl