Neck pickup simulation

[bancika]

I've recently started a new project, headless travel guitar that will have only bridge pickup (dimarzio chopper). I thought about having a push/pull switch that will activate some sort of circuit that simulates neck pickup. Guitar that inspired my build has dimarzio twang king at the neck which is about a third of a power of chopper, so maaaybe I can get away with a passive circuit. Any ideas how I could accomplish this? The simplest one that comes to mind is to make a low pass circuit and tweak the output to match the expected output. Or maybe switch to parallel wiring and then cut some treble. If I can find a low loss eq circuit, I might make a tiny pcb with trimmers and have it tweakable. Or, if active circuit would bring something really good to the table, I could do that.

Any other ideas?

[Johan]

I don't think you can eq a bridge pick up into doing a neck pick up sound you'd be happy with for long. If you're building from scratch,  why not mount your one pick up on a rail and slide it into position? ...not pretty, but for a travel guitar? ....

[bancika]

Thanks for the response!

It's a travel guitar, but I plan to make it pretty, flame top, sunburst and all. Rail sounds like a cool idea but it's a lot of work to do and a lot of work to "switch" to neck position, I'd rather just put a neck pickup

[digi2t]

Bridge pickup, along with a push pull tone pot. Wire one side of the pot switch with a conventional tone cap arrangement, and the other with a Bill Lawrence Q-Filter. Add a treble bleed mod, and coil cut switch on the volume as well, if you so desire. No, you won't be getting any fat Straty rhythm tone a la SRV, but between the two different tone options, you should have enough tonal range to keep you happy.

You could cheat on the pickup placement as well, shifting it a bit towards the neck. The last guitar I built, the last things I did were the pup cavities. I jigged up the pickups upside down over the strings so I could then move them around, and zero in on what my ears felt was the best harmonic content. Once the measurements were recorded, strip down the body, and router the cavities. The only problem I foresee with cheating on the placement though is the pup interfering with pick. Food for thought.

[bancika]

oh yes, and it will only have one volume (push/pull) pot, no tone

[stm]

You should check these two MUST READ articles:

http://www.till.com/articles/PickupResponse/index.html
http://www.till.com/articles/PickupMixing/index.html

From the first, one, you can conclude that at very low frequencies a Neck pickup has about 12 dB more than a Bridge pickup.  At 100 Hz the difference is close to 10 dB.  This means that a 12 dB lowpass shelving filter that provides 10 dB gain at 100 Hz will get you closer (but not there).  The positions of the different notches that are produced are frequency/string dependant, i.e. not fixed, so there is little point in trying to approximate that aspect.  In any case I believe that this will be good enough for a travel guitar and wouldn't dismiss it without trying it first.  You can use any guitar to test to which extent the circuit approximates a Neck Pickup.

The second link is a sort of bonus, because I get from those graphs that by mixing Bridge and Neck pickups you get a sort of notch around 500 Hz.  Maybe a 12 dB deep notch seems like a representative average to try.

Combining the two above, I would use a dual opamp to implement the bass shelving filter and to buffer the 500 Hz notch.  A three-position (ON-OFF-ON) DPDT switch could well give the Brige pickup sound (just buffer), a fake Neck pickup sound (adding the shelving bass), and a fake Neck+Bridge (adding the shelving bass and the 500 Hz notch).

This sounds like an interesting project to try (at least to me!)

[bancika]

thanks STM, that's very useful. Now, that article probably assumes that the same pickup is moved from bridge to neck. In my case, I try to simulate a completely different pickup in the neck position. It's about 1/3 output of the bridge pickup (that is, under the same conditions) with tighter bass (and single coil). I'll try to avoid splitting coils because I don't like the noise. But having that in mind, maaaybe, I could get away with a passive shelving filter like this and avoid batteries.

Twang King

Magnet: Alnico 5
Output mV: 89
DC Resistance: 6.22 Kohm

Treble: 7.0
Mid: 7.0
Bass: 5.0

Chopper

Magnet: Ceramic
Output mV: 260
DC Resistance: 9.16 Kohm

Treble: 7.0
Mid: 6.0
Bass: 6.0

[Mark Hammer]

You know, if it was a PAF-sized humbucker, then maybe.  But the Chopper, while dual-coiled, is a single-coil dual-rail type.  Placed by the bridge, it's not going to have all that much bass response that you could easily mimic a neck pickup.

Not possible to wind yourself a thin pickup and wedge it against the end of the fingerboard?

[bool]

Imho, the neck pickup picks up a significantly different mix of string overtones, so just a "frequency shaping" won't do the trick. The easiest solution, imho would be to install some sort of a thin, single-coil sized humbucker in the neck position.

[bancika]

You know, if it was a PAF-sized humbucker, then maybe.  But the Chopper, while dual-coiled, is a single-coil dual-rail type.  Placed by the bridge, it's not going to have all that much bass response that you could easily mimic a neck pickup.

According to dimarzio website, chopper has a tiny miny more bass and power than the PAF

36th paf

Output mV: 250
DC Resistance: 7.31 Kohm

Treble: 5.5
Mid: 6.0
Bass: 5.5

Either way, thanks all for responses. I think I have a rough idea what my options are. I have a guitar that has relatively similar pickup now (FRED) and I have a 10 band EQ pedal, but also I can play with EQ through VST plugins. That should give me rough idea if active EQ-in will get me even to the ballpark. If yes, I might pursue it and make a simple EQ circuit (might need some help) to mimic what I did in VST. I can also try the passive circuit, it's easy to breadboard. If all that fails, I'll either have to live without the neck pickup or just get an Area-T or Twang King for the neck.

Btw, to those interested, here's how I plan to make it. Detachable neck, alder body with flame maple top, two tone sunburts. Hipshot headless system, thicker maple neck with jumbo gold EVO frets.



Cheers,
Bane

[Nasse]

whats the scale length?

[bancika]

Full scale but 20% smaller body. I already did something like that with les Paul. See http://diy-fever.com/guitars/mini-les-paul/

[bool]

I don't know if this goes against your design goals, but if you go with a "traditional" 2-pickup setup, imho a dual concentric pot (V+T) and a 3-pos B,B+N,N pu-switch would go nicely with this streamlined look/concept.

[Mark Hammer]

Full scale but 20% smaller body. I already did something like that with les Paul. See http://diy-fever.com/guitars/mini-les-paul/

Heh, heh, yeah the neck looks like it's for an 8-string against that body, until one realizes its the body that is smaller, not the neck that is bigger! 

[bancika]

I don't know if this goes against your design goals, but if you go with a "traditional" 2-pickup setup, imho a dual concentric pot (V+T) and a 3-pos B,B+N,N pu-switch would go nicely with this streamlined look/concept.

thanks. I definitely don't need a tone control. I have it on all most guitars and never use it. I am on the fence about the neck pickup. For this particular guitar I might be able to get away without it but I'm not sure. I tried playing with EQ in VST and it can make bridge pickup resemble neck, but not all aspects of it.

I gave it a little more thought and since I'm playing through VST almost exclusively these days, building an onboard EQ isn't very efficient because I can do it much better in VST. So I might leave the push-pull to be series-parallel switch for the bridge pickup and then add EQ on top of that.

Cheers,
Bane