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Trainwreck, what again? by ken Fischer
Before I continue, I would like to thank those people that provide me feedback, and questions, dealing with this column. I will continue with the subjects of pickups, controls, and wiring. That's because there seems to be some additional question about what I have written so far.
Chapter 3.0, the valley of doom!
What is a valley of doom? Something I should have mentioned at the outset of the pickup article. NEVER USE A SOLDERING GUN NEAR PICKUPS!!! Soldering guns are a powerful transformer that can weaken, and demagnetize certain magnets, that are commonly in used pickups. For an example, a soldering gun can erase most alnico magnets just as well as a tape eraser clears a recording tape. Soldering is a whole subject itself. I will say one thing about soldering equipment. That is to properly solder guitar pickups I personally, would only use a transformer operated, low voltage, temperature controlled, solder station, in the 25 to 50 watt range. Keep the main transformer of the station off to the side, at least a foot C25cm) away from any magnates. If you do not own, or have access to such a soldering station, bring your work to a professional who does. About 700 degrees-F, or 350 degrees -C is right for this kind of work. The same can be said for alnico magnets speakers. Although you are less likely to harm these with a soldering gun, why take chances?
One question I was asked by an owner of a Les Paul was, "I have a brightness cap on each volume control of my guitar. When both pickups are together, and I turn down one volume knob too far, it actually cuts high end. Did I make a wiring mistake?" the Trainwreck answer is no. volume "bright caps" are best used on one volume control guitars. They can be used on each volume control in a guitar such as your Les Paul. However, with both pickups on, the bright capon the pickup you turn down a bit, starts acting as a tone cap. It shunts highs to ground. Also, as you turn down the volume pot, it loads the pickup that is used on full, increasing this effect.
How about for a change of pace, I replay to an amplifier question?
On another website, M…mentioned, that I had told him that 220K was note the correct value for the grid return resistors, in a fixed bias, Fender, 6L6 equipped amp. To replay to M…, I'd like to say that the RCA tube manual says that 100K is the design max for this part. However, Fender, and most others have used 220K resistors, and these cause no problems at all. What can be noted is, that the resistor and the coupling cap from the phase inverter, from a RC network. The 100K value therefore makes for a faster response. Decreasing the typical .1 coupling caps to .02 will tighten the bass on these amps, for guitar, and also increase the response speed. When CBS took over Fender, they soon changed the 220K resistor, to 68K resistors in the Silverface Twin Reverb amp. Isn't that the amp everyone wants converted to blackface specs?
Back to the pickups wiring! Since we are talking wiring, let's talk wire. What type of wire is good to wire a guitar with? We first have to deal with the fact that two main styles of wire are used in guitars. One type is shielded wire. Shielded wire has one or more insulated conductors inside a tube of shielding material. This is most commonly tinned, braided copper. Sometime this shield is un-insulated, such as the wire used on classic Gibson pickups, and to wire their guitars. Sometimes the shield is insulated, as the wire in modern multi-conductor pickups is. The other wire commonly used is single conductor, non -shielded. This may be insulated or non-insulated in addition, in may be one solid strand, or a strand composed of many fine strands twisted into a single conductor. The wire is made of copper, but may be tinned to make it easy to solder. Teflon insulated wire is silver plated copper, instead of tinned. Teflon wire is rarely used in guitars. Cotton and PVC insulation is most often used. Cotton insulation cab be pushed back to expose the conductor. PVC wire must be stripped of its insulation, as must Teflon, to be soldered. I myself would not use cotton wire in amplifiers, where it has many problems. (But it doesn't rattle like PVC and Teflon wire in combo amps, hence its use) I don't find any problems with cotton wire in guitars, unless you live in a very damp area. PVC and Teflon do not absorb moister, salts, and rust like cotton, an advantage in that regard.
The next thing we need to know about wire for a guitar, is its gauge. The gauge is the diameter, or thickness of the wire, the gauge is very important when dealing with current, as too thin a gauge can overheat, burn out, or cause too much loss. A guitar pickup puts out so little voltage and currant, that the gauge is usually chosen for ease of wiring. Typical wire gauges in guitars are 20, 22, 24, 26, and 28 gauges. The higher the number, the thinner the wire. 42 gauge is a common wire gauge in pickup winding, to give an example of scale. Resist the urge to use lamp cord (typically 16 or 18 gauge) as guitar wire. It is too thick for many switch and potentiometer terminals, and looks awful inside your instrument.
I will not get into wiring diagram, as most pickup makers post these an their websites. The 120 sound diagram posted wit this column, was a sort of by accident. I sent it in to ask if the website had the ability to post such things. I guess we know the answer! In any case there wasn't an explanation sent by me for it. It is meant for a special purpose recording guitar, for studio players. You can take one guitar to the studio, and have a sound for almost any requirement. Used on a Les Paul for example, you would have 7 switches, and 4 controls to deal with. Of course this makes it quite complex to use during a live performance, which wasn't the idea. Of the many wired over the years, only two were used for stage performance.
I have a post office box address which you can write to with questions, comments, or suggestions. Be aware, I rarely get to this box, and because of many health problems, rarely send back replies. I will however read everything sent.
My address is: Trainwreck PO Box 261, Colonia, NJ 07067-0261 USA.
Until next time, all the best, Ken Fisher
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