Built in crossover for neck and bridge pickups

[callofcthulhu]

Wow so many replies overnight! You guys are awesome. Let me explain more what I'm trying to accomplish here, because there have been a lot of really good suggestion on how to get the results I want, but they require outboard gear that I'm trying to stay away from.
So here is the idea:
I only play at larger venues and churches with large sound systems capable of carrying my bass without and amp. I use IEM's, so basically no need to ever bring anything but my bass and tuner pedal. Hence I really don't want a biamping setup. Yes I could do two outputs into two DI's but then I would become a more high maintenance bass player, having to explain the the FOH guy what I'm trying to do and how to crossover the two inputs and such. As a FOH guy myself, that would drive me nuts if some bass player did that to me. I like being a low maintenance player, just plug in, nail the tunes, don't complain about the monitor mix, grab my check and leave. I'm sure it's the number 1 reason I get called back to gigs.

That in mind, I am going sort of for the Billy Sheehan idea, minus the distortion. Low pass the neck pickup around 100hz, high pass the bridge at the same point. Then add an active tone circuit that is an optical compressor/limiter to the bridge pup only. I love what compression does for my tone, adding so much clarity as well as cleaning up and evening out my attack. What I don't like is how i can't play as dynamically. By not compressing the neck pickup, I would still get dynamics in the low end, and the clarity and articulation in the mids and highs. I'd like it to be all onboard, as I would like to create a design for either a tone circuit or a bass brand that encompasses all of this.
I've had great success with this method tinkering in the studio with separate outputs, but have no idea how I could cross them over onto one output.

Okay now that you have the full story, let me hear your ideas! I think m0ses is correct I'm in over my head here, I have a basic understanding of wiring guitar electronics, and have come up with some cool hacks, but this is turning out to be much more complex than I expected.
Thanks!

Your described model is exactly how I use the stereo output of my Rickenbacker, though I actually do the opposite - I use a compressor on the neck so that the bottom end is present on every note, and use a high frequency expander on the bridge so I can still get more attack by digging in harder. I mix down to mono on my pedalboard before going to my amp.

I know next to nothing about electronics so I'll leave it up to you and the other posters to discuss the intricacies of your proposal. My contribution is that 100 hz seems awfully low to cut off the neck, there's a lot of woof and growl in the 200 - 400 range.

 

[fermata]

For the HPF, what you want is a capacitor in series with the signal path, to block out the lows, and a resistor parallel to capacitor to bleed a bit of signal through.
For the LPF, you want a capacitor parallel to the signal path, to shunt high frequencies to ground. You need a resistor between the pickup/capacitor circuit and the rest of the circuit, however, to isolate the pickups from each other.

I've done some mods somewhat to this effect on my Hofner (although with no resistors in the circuit I guess they're not technically LPF and HPF filters).

Essentially, I've wired the pickups like a Jazz Bass (both pickups are affected by a treble cut tone control). The twist is with the bridge pickup, where I can switch in a series-wired bass-cut cap. (It's basically Rickenbacker's 'vintage switch' with a different cap value--I chose .01uF to let more bass and mids through than the .0047uF Rickenbacker uses.)

In addition to cutting the lows, the big benefit is that it changes how the pickups interact for the better. With the cap engaged, I can run both pickups up full without any phase issues, etc. And the bridge pickup almost becomes like another tone control, allowing me to dial in more clarity and articulation, regardless of my treble cut tone setting.

Try the cap in series with alligator clips (and test a few different values while you're at it--.01uF and smaller); if you really like the effect, you could pretty easily just hardwire the cap to the bridge pickup volume pot (between it and the output), or put it on a DPDT toggle (or push-pull knob) to make it switchable. (If you ever want to favor or solo the bridge pickup, you need to be able to switch out the cap.)

Here's a diagram for the switch:

 

[Bassamatic]

At a quick glance - I would think that you cannot have anything in the HPF and LPF shunting to ground because it will affect both pickups in this passive setup - everything has to be in series mode with each pickup to keep isolation. It seems that you would need a series cap for the HPF, and and series inductor for the LPF. You will have to calculate these values knowing the REAL AC impedance (not resistance) values of the pickups to be accurate. This is how caps and inductors are used in passive speaker crossovers. Since this will be a very simple circuit - you will get only about -3dB at the crossover point - that may not be enough to avoid phase issues. You might want to move the -3dB points a little apart from each other, effectively creating a "notch" at the crossover deeper than 3 dB. I wouldn't know where to suggest your start - maybe around 250 Hz? Anyway - good luck with this - keep us posted.

Edit - I sent an email to my genius audio engineer about this - I'll let you know what he says.

 

[GunsandGuitars]

Your described model is exactly how I use the stereo output of my Rickenbacker, though I actually do the opposite - I use a compressor on the neck so that the bottom end is present on every note, and use a high frequency expander on the bridge so I can still get more attack by digging in harder. I mix down to mono on my pedalboard before going to my amp.

I know next to nothing about electronics so I'll leave it up to you and the other posters to discuss the intricacies of your proposal. My contribution is that 100 hz seems awfully low to cut off the neck, there's a lot of woof and growl in the 200 - 400 range.

Tell me how you mix them down to mono on your pedal board? Though I really want this to be all onboard, I'm starting to think that using a TRS cable into a pedal or DI that houses the crossover, compressor, and mixes down to mono output (either 1/4" or XLR) might be the solution. It could even be phantom powered perhaps? Then I would just use a switch like your ric to route both pickups to mono output to be used with a standard 1/4" if the pedal/DI gets lost, broken, or just not necessary for the gig. Still hoping for an onboard solution though

 

[GunsandGuitars]

I've done some mods somewhat to this effect on my Hofner (although with no resistors in the circuit I guess they're not technically LPF and HPF filters).

Essentially, I've wired the pickups like a Jazz Bass (both pickups are affected by a treble cut tone control). The twist is with the bridge pickup, where I can switch in a series-wired bass-cut cap. (It's basically Rickenbacker's 'vintage switch' with a different cap value--I chose .01uF to let more bass and mids through than the .0047uF Rickenbacker uses.)

In addition to cutting the lows, the big benefit is that it changes how the pickups interact for the better. With the cap engaged, I can run both pickups up full without any phase issues, etc. And the bridge pickup almost becomes like another tone control, allowing me to dial in more clarity and articulation, regardless of my treble cut tone setting.

Try the cap in series with alligator clips (and test a few different values while you're at it--.01uF and smaller); if you really like the effect, you could pretty easily just hardwire the cap to the bridge pickup volume pot (between it and the output), or put it on a DPDT toggle (or push-pull knob) to make it switchable. (If you ever want to favor or solo the bridge pickup, you need to be able to switch out the cap.)

Here's a diagram for the switch:

This sounds like what I'm after here. But how does the "ric switch" with the cap only affect the bridge and not affect both pickups if they are routed to the same output? I thought that was my problem to begin with. I'll try scratching up a diagram with your mod in it and maybe it will make more sense to me

 

[callofcthulhu]

Tell me how you mix them down to mono on your pedal board? Though I really want this to be all onboard, I'm starting to think that using a TRS cable into a pedal or DI that houses the crossover, compressor, and mixes down to mono output (either 1/4" or XLR) might be the solution. It could even be phantom powered perhaps? Then I would just use a switch like your ric to route both pickups to mono output to be used with a standard 1/4" if the pedal/DI gets lost, broken, or just not necessary for the gig. Still hoping for an onboard solution though

Just a standard buffered blender pedal with the neck signal chain ending on the "in" and the bridge signal chain ending on the "return" (nothing connected to the "send"):

Blender V1 : Wounded Paw, Bass and Guitar Effects and Blenders

 

[fermata]

This sounds like what I'm after here. But how does the "ric switch" with the cap only affect the bridge and not affect both pickups if they are routed to the same output? I thought that was my problem to begin with. I'll try scratching up a diagram with your mod in it and maybe it will make more sense to me

I don't have a good theoretical answer--but in practice, it works. Here's the full diagram showing the mods to my Hofner; on a more typical bass, the tone pot would be in place of the re-purposed Rhythm and Bass On switches.

EDIT: There were a couple of errors in the previous diagram, so here's a corrected version. (I've been through a variety of mods along these lines. At one point, I had separate treble cut caps for each pickup, but I ended up not liking that, so this is where I've settled--simple but very versatile.)

 

[GunsandGuitars]

I don't have a good theoretical answer--but in practice, it works. Here's the full diagram showing the mods to my Hofner; on a more typical bass, the tone pot would be in place of the re-purposed Rhythm and Bass On switches.

now that I look at it, maybe it's because the bridge pup comes first in the circuit, so cut the lows first, then add the lows back in from the neck pup after. As opposed to cutting the lows from the bridge after the neck pup, effectively cutting from both? I'll start over on my diagram yet again haha

 

[callofcthulhu]

BTW I'm very interested in following the development of this idea.

Reminds of some of the early "recording" instruments made by Gibson and Alembic.

An XLR out on the circuit, with phantom power running the whole thing, would be super slick.

 

[GunsandGuitars]

Just a standard buffered blender pedal with the neck signal chain ending on the "in" and the bridge signal chain ending on the "return" (nothing connected to the "send"):

Blender V1 : Wounded Paw, Bass and Guitar Effects and Blenders

So does that thing have a TRS input that blends into a TS output? The description isn't very clear

 

[callofcthulhu]

So does that thing have a TRS input that blends into a TS output? The description isn't very clear

Nope, it's all mono.

I use a stereo to dual mono cable out of the bass itself:

https://www.amazon.com/Hosa-STP-204...coding=UTF8&psc=1&refRID=YETYHX3TFY0ERW2S8WSV

 

[fermata]

now that I look at it, maybe it's because the bridge pup comes first in the circuit, so cut the lows first, then add the lows back in from the neck pup after. As opposed to cutting the lows from the bridge after the neck pup, effectively cutting from both? I'll start over on my diagram yet again haha

I just realized there were two mistakes in the diagram I posted (holdovers from previous versions of my mods), so I've posted a corrected version above. Things might make a bit more sense!

I think the reason the bass cut cap only affects the bridge pickup is that it's because the volume controls are isolated/operate independently with J-bass wiring (pickup outputs go to the the center lug instead of the outer lug). When switching in the .01uF cap, it's simply putting it in series with the signal going from the bridge pot to the output.

 

[jw23mind]

At a quick glance - I would think that you cannot have anything in the HPF and LPF shunting to ground because it will affect both pickups in this passive setup - everything has to be in series mode with each pickup to keep isolation. It seems that you would need a series cap for the HPF, and and series inductor for the LPF. You will have to calculate these values knowing the REAL AC impedance (not resistance) values of the pickups to be accurate. This is how caps and inductors are used in passive speaker crossovers. Since this will be a very simple circuit - you will get only about -3dB at the crossover point - that may not be enough to avoid phase issues. You might want to move the -3dB points a little apart from each other, effectively creating a "notch" at the crossover deeper than 3 dB. I wouldn't know where to suggest your start - maybe around 250 Hz? Anyway - good luck with this - keep us posted.

Edit - I sent an email to my genius audio engineer about this - I'll let you know what he says.

+1 on 250Hz crossover, I'd say between 200-250Hz. Also, no problem with "only -3dB at the crossover", re phase issues; the phase shifts only increase away from each other around the crossover point, if you separate the -3dB points; in fact this is part of what creates the notch as the phase shifts become significant. A 1st-order crossover (-3dB at crossover) recombines quite nicely assuming no other phase shifting before recombination. I'm imagining that putting a compressor on one of the channels thus split could cause problems if not done carefully, not only from phase shifts or inversion generated by the compressor circuit, but simply for the fact that gain is changed relative to the other channel as well.

 

[jw23mind]

Tell me how you mix them down to mono on your pedal board? Though I really want this to be all onboard, I'm starting to think that using a TRS cable into a pedal or DI that houses the crossover, compressor, and mixes down to mono output (either 1/4" or XLR) might be the solution. It could even be phantom powered perhaps? Then I would just use a switch like your ric to route both pickups to mono output to be used with a standard 1/4" if the pedal/DI gets lost, broken, or just not necessary for the gig. Still hoping for an onboard solution though

Just two resistors coming together from each pickup or crossover/compressor output for a passive mixer, of high enough value so as not to excessively load each pickup, say 100kOhm. Add a single inverting op-amp and you've got an active mixer.

 

[GunsandGuitars]

+1 on 250Hz crossover, I'd say between 200-250Hz. Also, no problem with "only -3dB at the crossover", re phase issues; the phase shifts only increase away from each other around the crossover point, if you separate the -3dB points; in fact this is part of what creates the notch as the phase shifts become significant. A 1st-order crossover (-3dB at crossover) recombines quite nicely assuming no other phase shifting before recombination. I'm imagining that putting a compressor on one of the channels thus split could cause problems if not done carefully, not only from phase shifts or inversion generated by the compressor circuit, but simply for the fact that gain is changed relative to the other channel as well.

You guys could be very right, I don't remember what frequency I used last time I did this in the studio. I'll be doing some R&D on the best frequencies to use, as well as what resistor/capacitor combo to get the desired frequency response. But first I want to make sure it's possible before I devote that much time and energy to the project.

 

[GunsandGuitars]

Just two resistors coming together from each pickup or crossover/compressor output for a passive mixer, of high enough value so as not to excessively load each pickup, say 100kOhm. Add a single inverting op-amp and you've got an active mixer.

That would do it. I did find a dual instrument buffer/mixer pedal with an effects loop for one of the channels. I could run the compressor thru the loop for the bridge pickup, and mix the volume on the pedal to match the lows from the neck. Assuming I could mod the pedal to house everything this wouldn't be a bad solution, but still more complicated than I want.

 

[GunsandGuitars]

I'm starting to think that the solution is that I need to learn how to build an active preamp. Because I could get a similar effect if just installed two preamps, one on each pickup, and cut the highs on the neck preamp, and cut the lows on the bridge preamp. The problem is that I'd be cutting around 60hz for the bass, and cutting around 4khz for the treble, leaving a large mid range in for phasing. But if I could build preamps that boost/cut at the frequencies I want, then I could make it more like an active crossover. Does anyone have any good resources on how to build preamps?

 

[micguy]

I have basses wired in what I call a bridge/woofer configuration. If you put the pickups in series, but shunt the neck pickup with a fairly large value capacitor (depends on the pickups you're using what value works), what you get is the low frequency output from the neck pickup, and the bridge pickup runs full range. This is a cool sound - it has the mid and high frequency reponse of a bridge pickup, but the low end of the neck pickup. From there one, I do other things, but if you want to send separate outputs, you can do something very similar, but very simple:

1) Wire the neck pickup to one output jack, and shunt it with a cap. Something in the range of .1uF is a place to start, season to taste after that.

2) Wire the bridge pickup to the other jack. You can wire a tone control to this as well. Although you can think about hi pasing this, there is a lot less low end in the bridge pickup; I'd suggest you try it without hi passing to start - it'll probably work fine.

After that, do what you want with the two signals - compress one, flange the other, whatever.

 

[fermata]

I have basses wired in what I call a bridge/woofer configuration. If you put the pickups in series, but shunt the neck pickup with a fairly large value capacitor (depends on the pickups you're using what value works), what you get is the low frequency output from the neck pickup, and the bridge pickup runs full range. This is a cool sound - it has the mid and high frequency reponse of a bridge pickup, but the low end of the neck pickup.

Good call! I did this with a MM pickup on a former bass of mine, mimicking the G&L 'OMG' setting (a .1uF cap across one of the coils), and it was a great sound. I can only image the effect would be more dramatic on more widely spaced pickups!

If the OP wants to go active, more power to you, but here's a very simple circuit idea for a low pass/high pass configuration: put a .1uF cap in parallel with the neck pickup (from the center lug, so it only affects the neck pickup) and put a .01uF cap in series with the bridge pickup. (It would probably be worth experimenting with different cap values to find the best ones for your pickups.)

 

[GunsandGuitars]

I have basses wired in what I call a bridge/woofer configuration. If you put the pickups in series, but shunt the neck pickup with a fairly large value capacitor (depends on the pickups you're using what value works), what you get is the low frequency output from the neck pickup, and the bridge pickup runs full range. This is a cool sound - it has the mid and high frequency reponse of a bridge pickup, but the low end of the neck pickup. From there one, I do other things, but if you want to send separate outputs, you can do something very similar, but very simple:

1) Wire the neck pickup to one output jack, and shunt it with a cap. Something in the range of .1uF is a place to start, season to taste after that.

2) Wire the bridge pickup to the other jack. You can wire a tone control to this as well. Although you can think about hi pasing this, there is a lot less low end in the bridge pickup; I'd suggest you try it without hi passing to start - it'll probably work fine.

After that, do what you want with the two signals - compress one, flange the other, whatever.

Okay so I dug up some old tracks that I toyed with this on, biamping the neck and bridge with a crossover at 100hz, which is definitely where I want the crossover to be. Higher than that and it gets too muddy, the bridge pickup does a better job at getting tighter focused frequencies in that 100-200hz range, the neck adds a lot of "oomph" below 100hz that the bridge lacks. I tried taking off the high pass on the bridge to see how it sounded with the low pass on the neck only and bridge wide open, and there is still a phase issue that loses a little low end and adds some mud. So I definitely want to high pass the bridge as well if I'm gonna go thru all this trouble.