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Rewiring a Humbucker for coil tapping and phase reversal. See the Les Paul Humbucker page for photographs of an actual modification. The following considers modifying the bridge pickup only; it is possible to apply the same mod to the neck as well, which will increase your options tremendously. However, working inside a Les Paul cavity is not the easiest of options and undertaking both pickups is quite a job. The following will give very pleasing results. A word of caution before you start this job - make sure you can finish it. Modifying pickups is really fiddly and requires top quality soldering, a small slip with cutters or soldering iron can render a lovely very expensive instrument tatty looking. Remember also that the next people who will judge your modifications will be the audience and a guitar, which crackles or suddenly goes silent does leave a lasting impression with people. So, if you are still keen and confident read on. You will need two tone pots, which incorporate a switch; the pull types with a double pole changeover switch are ideal because these can directly replace your existing tone pots. Do not be tempted into drilling an expensive guitar, an extra hole can knock your value down by 25%. Before you start or unsolder anything make sure that the guitar cavity is deep enough to take these pots. Firstly strip down the bridge pick up and disconnect the coil connection from the pickup chassis, also find the point at which the two coils are joined and solder a fresh lead to it – this is the centre tap. You should now have three connections all going to the coils, one to each end and one to the centre tap. All three connections should be connected via shielded cable and the three outer shields (braiding,) should be soldered directly to the pickup chassis and the cables carefully threaded through the pickup outlet hole. At this point you should have a total of six electrical connections; three wires to the coil connections and three shields all going to the pickup chassis, you are only going to connect the other end of one these shields so insulate the other two. You now have four connections, three to the coils and one to the pickup chassis. This is the pickup modified and the cover may now be replaced and resoldered if necessary. As a precaution you may measure the resistance of the coils with an ohmmeter. The measurement from the centre tap to either of the other connections should be about 3000ohms, the measurement between the two outer coil ends should be about 6000ohms and there should be no measurement between any of the coil connections and the pickup chassis. The values of 3000 & 6000 ohms are approximate and will vary with each pickup but the centre tap should always be half of the total. Next step; replace one of the tone controls with a pot, which includes a pull switch. Wire the outer two connections through the switch so that when the switch is pulled it reverses the coil connections. This means that alternatively one is `hot` and the other `ground` - this is now the phase reversal switch. Next. Replace the other tone control with a pull switch type control and wire it so that when the switch is pulled up the centre tap of the coils in connected directly to ground. This effectively turns the bridge pickup into a single coil pickup. All three connections to the pickup coil will have screened braiding and they all should be soldered to the pickup chassis. However, only one of the braids should be connected to the guitar ground (earth). Connecting all three may cause an effect known as an "Earth loop" so remember to insulate the two that you don't connect. It is usual to use the pot covers as earthing points so remember to solder the earthing connection which was on the old tone control covers to your new ones. Apart from the tone control connections the centre tap control should now have two connections to the switch, one to the centre coil tap and one to earth (ground.) Whilst the phase reversal switch should have all six connections used up to fully reverse the coil. Now what we have is a bridge pickup, which may be switched in and out of phase with the neck one and may also be converted into a single pickup. When the pickup selector is in centre position (both pickups on) a breathtaking new range of sounds are available by placing them out of phase with the bridge acting as either a Humbucker or single coil. As the two vol. controls are adjusted the amount of phase cancellation can be varied. The`acoustic` sound I refer to is the Humbucker out of phase, which also sounds great through a chorus. Gibson vol. pots are more expensive that other makes but they are very well made and stay in the position you turn them to. This is why I use the tone pots as the replacements as these are not critical. Try to get 500k pots as these give better treble response. Vol. pots should be `audio taper` (logarithmic) and tone pots should be `linear`, if you are unable to get linear pots for the tone you can get way with logarithmic but you will not get away with replacing vol. pots with linear ones. Almost all pots with switches are supplied as logarithmic. A word of caution, this is a long job there is no way of rushing it (takes me a full day's work,) and you need to make sure your soldering is tiptop. If soldering or engineering is new to you it is wise to spend some time practising on things that don't matter - that doesn't include a Gibson! If you fancy making the modification but don't fancy dismembering your pickup I undertake pickup modification by post for you to refit into your instrument. .oOo. |