The schematic you have is for the Pro basses, right? That's quite a different animal than the custom -- although I understand the pickups are more or less the same except for the way it's wired up internally.
Yes, it's the Pro schematic. It's a pretty simple JFET preamp. It has a passive tone control before the buffer FET. Each pickup has its own buffer, and each of those buffers has a low/mid boost switch. Each buffer section has a volume control for that pickup. The volume controls then feed a two FET mixer, which also has the "pick attack" switch. The output of the mixer is then routed to the output jack and DI transformer and ground loop switch.
I will be using the original circuit as a starting point. My plan is to add a low pass filter, but keep the boost switches. I'm also going to eliminate the DI parts. First I have to build one as shown in the circuit and see how it sounds... it's a very simple circuit... but simple is good.
The pickup you've got may be one that was intended for a passive Wal (they did make a small number of them) , or it may have been modified prior to your getting it.
Except for the color codes of the wires, the pickup is wired up exactly as shown in the schematic. The pickup is not modified since the coils are soldered to a printed circuit board, and the board is responsible for the series connections of the coils, as well as the 5 wires coming from the pickup. The only way to get a hot wire from each coil would be to modify the circuit board by cutting the trace between coils. The coils have no wires at all coming from them, except to the circuit board. At each end of the row of coils is the trace on the board, the far end loops back under the coils so that all the pads for the hookup wires to solder to are at the left side of the pickup.
From my understanding, the passive basses used the same pickups.
This pickup did not have a connector on the end, but the wires also appear to never been seen solder. As far as I can tell the pickup is new, and had never been opened. It was quite glued together with wax, so after removing the screws that held it together, it need a slight coaxing to come apart. Afterwards it opened up quite easily. So if someone had opened it previously, it wouldn't have been so tricky opening it up.
As you know, the standard custom pickups give you a common ground and a hot for each series pair of coils, per string. Is the one you've got your hands on done some different way?
This pickup has five wires, but they are a common ground, and two pairs of wires from each row of coils. They are not a common ground and one wire for each string pair of coils. It's wired exactly like a four conductor humbucker. Each row of four coils is equivalent to one coil on a regular humbucker.
The schematic shows 5 wires coming from the pickup, and at the preamp's connector the two rows of coils are connected in series.
I don't actually know anything about the Custom pickups. I have seen one photo of another Wal pickup from a website, and that has 5 wires going to a connector, and you can see the circuit board is similar, but the coils seem to be set with a slightly wider aperture than the pickup I have here.
You can see by this photo that they do not have a separate wire for each coil pair. The top and bottom edge of the circuit board shows the series connection between coils.
The photo of a Wal pickup off the 'Net:
http://walbassist.blogspot.com/
The caption reads:
Wal Bass Pickups
All Wal pickups were handmade in Pete's shop. The current "Custom" instruments include bridge and neck humbucking-style soapbar pickups. However, inside each pickup casing there are actually two individual pickups per string, each with magnet, wound bobbin and adjustable pole piece. Apparently the bobbins are wound in an opposite direction so that each pair creates the "humbucking" effect.
As there are two pickup casings, there are four individual pickups for each string (4,5 or 6) on Wal Custom bass models. Extremely precise adjustments can be made to the balance and tonal output of each string. The combination of the Wal pickups and Wal preamp provides the lowest possible noise and intermodulation distortion levels with the highest possible dynamic range and optimal signal headroom.
Note: this info is incorrect, as each coil does not have its own magnet. Also the coils are not wound in opposite directions. As with just about every humbucker on the planet, the coils are just wired up in reverse.
Unless someone can show me a pickup wired different I'll have to assume they are all wired this way.
Here's Joe's pickup:
At the same web site they show the preamp controls from the Wal manual. There no trim pots to balance each string pair, so I have to once again assume that the pickups on the Custom are not wired up like that. If someone here has a Custom and wants to tell us, feel free do so.
http://photos1.blogger.com/blogger/7461/3137/1600/controlcavity.jpg
I guess the most flexible thing to do would be to take the start and finish of each coil out and let the buyer wire it up however they like, but that might be kind of unweildy! I'm thinking a 6-string would have 24 wires coming from each pickup, plus sheilding (!!!)
Yes, that would be the most flexible thing... however, flexible for what? The tone of one 2.5K coil buffered will sound totally different from the sound of 4 or 5 of those in series buffered, or 8 or 10 of those in series.
The only real benefit from having separate coil outs is to get a low impedance tone. And some people don't like that tone. I was making pickups that were basically like two of these coils in series, and some people felt they were too thin sounding. I liked the tone, however.
There's little point in manipulating the series connections across coils because you will have some strings louder than others, and with different tonalities for each string.
The last thing I would want is a nightmare of having the new owner of a pickup with 17+ wires asking how to wire it up! You see what problems people have here with simple wiring. I can supply anything someone might want though, within reason, on a custom basis. When I was younger I did crazy wiring on my basses too.
You will get a clearer tone just by virtue of having multiple smaller coils. Having each string pair get its own buffer could be cool, as long as you wanted a very clear bright tone. It wouldn't be that thick Wal tone. You could even EQ each string, or do stereo panning, but that's not very useful for bass.
OK.. having said all that. My plan is to evaluate what the stock pickup sounds like, and then I'll make my own version and see what that sounds like. At that point I will decide what would work best for my version. So multiple outputs is obviously an option, and something you can't get from the original, which you can't get anyway.
