Some bass wiring help- attenuating pickup modes

[Eddododo]

I know it's not a stompboxes thing but I value the insight of this forum too much.
I have a bass with 2 humbuckers with their coils wired in series- they are tuned very dark and I already know that the parallel arrangement sounds quite good and bright for slapping. I'm considering a switch for the neck pickup series/parallel. The problem is that the series arrangement is about twice as loud as parallel. My idea is to add attenuation for the series arrangement and to bypass the attenuation for the parallel mode.

Would this work well? Is there a more elegant solution? should I do it using voltage divider's rather than a variable resistor? FYI the attenuating varistor goes into an MN blend pot so it would be lowering the volume as if it were a part of the potentiometer.

Thanks!

[Eddododo]

I just had an epiphany I think- the pickups would see a different load then... so I would need to do a voltage divider such that R series + parallel resistance of shunt and pot to ground = original pitpotload

[DavidRavenMoon]

You can use a series resistor to reduce the output in series. It will probably dull the tone a bit. Don't use a voltage divider (like a regular volume control) as that will introduce more loading and dull the tone more.

If the bass had a preamp this would be much easier (and they wouldn't be so muddy)

Some humbuckers like MM types were never meant to be used in series, or passive. So they get muddy.

You might want to try the pickups in parallel and then adjust the EQ on your amp to get the tone you want.


Sent from my iPhone using Tapatalk

[Eddododo]

If I use 250k in series and a 500k shunt in parallel with the pot the pickup would see the same load, yes?

[ashcat_lt]

First, just to get it out of the way, you're missing a ground connection for the bottom pickup.  A minor oversight, I'm sure.

The issue is not the load that the pickup sees.  You'll get a tiny bit more bite out of the pickup itself, but on a series-wired HB it can't go too far, and you might actually dig it.

Except you probably won't hear it because all that extra series resistance is going to work against cable crapacitance and kill whatever treble you might have gotten out of it.

There isn't really a great way to do this, but if you really think you want to, I think the best you'll get would be basically individual V pots with carefully tuned "treble bleed".  Unfortunately, though, "treble bleed" actually means "shelving low high pass", and you'll end up losing at least some of the meat from series setting.

[DavidRavenMoon]

If I use 250k in series and a 500k shunt in parallel with the pot the pickup would see the same load, yes?

Don't use the shunt. You already have a volume pot in the circuit. Assuming that's 500k, an additional 500k resistor will drop the load to 250k.

And how did you decide to use a 250k series resistor? That will drastically cut your volume. You can wire up a trim pot like a variable resistor (i.e. no connection to ground) and dial it in. I'd bet you don't need much past 10k.


Sent from my iPhone using Tapatalk

[MrStab]

probably a stupid idea, but is there maybe something you can do with a small audio transformer? maybe wired in parallel when in series mode? i have no idea how that would sound or respond, just putting it out there.

[Eddododo]

If I use 250k in series and a 500k shunt in parallel with the pot the pickup would see the same load, yes?

Don't use the shunt. You already have a volume pot in the circuit. Assuming that's 500k, an additional 500k resistor will drop the load to 250k.

And how did you decide to use a 250k series resistor? That will drastically cut your volume. You can wire up a trim pot like a variable resistor (i.e. no connection to ground) and dial it in. I'd bet you don't need much past 10k.


Sent from my iPhone using Tapatalk

I guess I was thinking about 'half' as a starting point. The manufacturer describes series:parallel as about 2:1. I'll assume a grain of salt with that but still seemed like a ballpark to start in and my thought process to get to half made 250 to a 250 shunt a simple solution. I admittedly don't have a great grasp of impedance and loading with regard to pickups and their resonance etc.
Sonia what the pickup 'sees' really a non issue in this case, or am I so off concept that I'm not even asking the right question.

[ashcat_lt]

It's kind of a complex system, but basically you've got an LR lowpass consisting of the inductance of the pickup and then whatever load.  Series resistance will tend to raise the cutoff of that.  But then you've got the RC lowpass of the series resistance over the capacitance of the cable, and that cutoff will get lower as the resistance gets bigger.  I think that resistance between the inductance and capacitance tends to also keep them from creating quite as much resonance, but that's not the big issue. 

"Everybody" knows that turning down your V pot causes a loss of high end.  That's mostly because the series resistance gets big.  That's why people put "treble bleed" caps across those pots.

Conversely, the T pot works for most of its travel by reducing the resistance to ground ("loading the pickup"), working against that inductance we talked about.  In fact, most of the point of the Tone cap is to keep that filter cutoff from getting too low as you turn the pot down.