Category Archives: Guitar

Guitar Fetish “Gold Foil P90 Humbuckers” – in a Les Paul

My Gold top

My Gold top

I’ve owned my Gibson Les Paul Deluxe (made somewhere between ’75 and ’77) since about 1991. It came with P90 pickups, which sound glorious. They’re definitely thinner than your regular humbuckers, but thicker than Fender single-coils. I don’t like mushy tones, so this combination is great for me. The only trouble is, they are really noisy. This is exacerbated by the modern world, which is full of computers (and phones) and Compact Fluorescent bulbs, which all put out a lot of RF interference.

One possible solution was to fit normal humbuckers to my LP, but that would require destructive routing. I chose to go for some P90 sized humbuckers instead…..some of these from Guitar Fetish. They’re the right size, and they’re humbuckers!

Fitting them was relatively easy, just a 20 minute job. The only problem that presented was that the new covers didn’t want to fit inside the old routes, so I tried the old covers and they fit over the new pickups perfectly. So now I have retained the look of the originals.

Some observations:

  • These are very quiet P90-like pickups
  • The P90 style pole pieces are just for show. These humbuckers have blades inside the coils.
  • As you can see from the photos, the gold foil isn’t visible due to my use of the old covers.
  • The neck pickup is very loud, whereas the bridge pickup isn’t so much. Time will tell as to whether this is an issue.
  • I’ve yet to compare them to my Telecaster, but is suspect these gold foils are louder.
  • I need to replace the potentiometers as they’re quite corroded. Time to get some CTS pots, or perhaps splash for an Emerson set.
Original P90 neck pickup

Original P90 neck pickup

Original P90 neck pickup and new Gold Foil

Original P90 neck pickup and new Gold Foil

Gold foil cover doesn't fit, so here's the old cover on the new pickup

Gold foil cover doesn’t fit, so here’s the old cover on the new pickup

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Rewiring a Telecaster with a four-way switch

Conventional 3-way switching

IMG_2158I’m willing to be that 99.9999999% of Telecasters are equipped with the conventional 3-way switch that offers up the bridge pickup, the neck and bridge in parallel, and then finally the neck pickup on its own. Time has shown this to be perfectly satisfactory as those 3 different tones have been and continue to be “go to” tones for musicians world-wide. My interest in Telecasters comes from a range of guitarists:

Mark Knopfler

He used one on many tunes like Espresso Love, and even the grotesque Walk Of Life. His Tele tone was always fat and chunky. I don’t know which Tele he used on early tracks, but since late ’79 he used ones built by Schecter back when they really built custom guitars.

George Harrison

He’s famous for his gorgeous rosewood Telecaster, which he used to great effect on “I Want You (She’s So Heavy)”. You can hear him switching between neck and bridge as he plays over verse and chorus, and then the big riff at the end as he grinds through on the bridge pickup.

Joe Walsh

One of my favourite solos ever is the two-player epic that is Hotel California. A fantastic battle between Don Felder on a Les Paul and Joe Walsh on a Tele. You get to hear the difference between the two guitars…the thick bite of the Les Paul, and the sweet glassy edge of the Tele (probably set to both pickups in parallel…the normal middle position).

Conventional 3-way pickup wiring for Telecaster

Conventional 3-way pickup wiring for Telecaster

Why 4?

Over the years I’d always heard that one could get different tones out of a Tele by wiring the middle position so the pickups were in series, rather than in parallel. And that this would give you a “big sound”. That didn’t make much sense at the time, but as I hadn’t ever heard this configuration, I had no reason to doubt it. But I had to try it myself one day.

Recently I spotted a pre-wired kit from Emerson that went for about $65. They do such a lovely job of the wiring I seriously considered getting one. But that’s cheating, so I bought essentially the parts for it from Stewart McDonald so I could build it myself.  Here’s the parts kit. They also sell the ludicrously expensive capacitor that Emerson includes.

telecaster-4-way-wiring

The alternate 4-way switch wiring diagram

Pickups

My lovely wife bought me a set of “Vintage Noiseless” Telecaster pickups, made by Fender. That’s just how lovely she is. So this was a perfect time to install those too. I had originally installed a Schaller telecaster pickup in the bridge and a no-name neck pickup. They sounded OK, but in this modern world of computers-as-tape-recorders and compact-fluorescent bulbs, they were very, very noisy. Second only to the P90s in my Goldtop, but that’s another story. A third reason for doing this is that the cheap Japanese 3-way switch I’ve had in it for almost 15 years was failing quite quickly.

So, the wiring wasn’t hard. The only thing that slowed me down was I decided to use the fabric covered wire that came with the StewMac parts kit. I;d never used it before. You’re supposed to cut to length, and then push the fabric back to revel tinned wire. All cool so far, but then the fabric springs back making it a little hard to solder even if you get a good mechanical joint. I’m used to using Teflon covered wire that I strip before soldering. Anyway, it looks cool, so I won’t whine too much. Here’s some photos.

Here are the noiseless pickups sat waiting for me to begin removal of the old pickups.

Here are the noiseless pickups sat waiting for me to begin removal of the old pickups.

Wiring complete!

Wiring complete! You can see the ludicrously overspecced 200 volts capacitor, from Emerson.

Re-assembled and re-strung

Re-assembled and re-strung

Sound demo

The only thing left to do was to plug it in and see what it sounds like. Here’s a quick recording of me noodling around in Em, and switching between each position. This is plugged straight into my AX84 single-ended tube amp, set to be somewhat crunchy, into my 2×12 cab with celestions. Recorded with an SM57 right into a Mac.

I begin on the bridge pickup. The switch to neck and bridge (parallel) is at 1:49, the switch to neck alone is at 2:43, then to neck and bridge (series) at 4:14.

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A real effects pedal power-supply

BatteriesWhy?

Over my playing years (more than 30 now) I’ve owned many effects pedals, spent a ton on 9V batteries and even tried many different power supply devices. I had one of those VisualSound “1-Spot” daisy chain things, which worked quite well. And recently I was given a Furman SPB-8 which appears to be the mother of all pedal boards. If you’ve been to this site before you know I’ve built an amp, and a whole slew of different pedals. All of these things I mention have one thing in common: there’s a lot of attention paid to converting alternating current from the wall outlet into direct current to power the circuit.

How?

After looking at many different power supply circuits, I realised they looked very simple, but I did not know the first thing about why each component was there and what they did.

My cousin Mike was in need of a power supply for his pedal board that could handle anything that he threw at it (i.e. multiple voltages and a useful current handling capability). Naturally there are products one can buy, such as the Voodoo PedalPower or the MXR Brick, but these can be quite expensive. And lets face it, I wanted to build one, so I could find out how they work.

What?

So, what does this thing need to do? Basically the following is desirable:

  • Provide a steady 9 volts.
  • Do not introduce noise into the circuit.
  • Handle at least ten pedals’ loads, which might approach 1 Amp.
  • Be small enough to fit under Mike’s pedal board.

Transform, rectify, smooth and load

From my work with tube amps and reading everything I could find in print or online, it became clear that, at a fundamental level, there are only a few discrete steps to accomplish:

  1. Transform the outlet supply from 115V to something closer to the desired voltage.
  2. Use a rectifier to convert the AC supply to a DC supply.
  3. Use filters to smooth out the now rippling DC.
  4. Load the circuit with whatever you wish to actually provide power. Whatever that is, it require voltage, will draw current and therefore has resistance.

A transformer is easy to get hold of. Even Radio Shack sells a 9V AC ‘wall wart’ that will handle 1 amp. A rectifier is easy too; just a bunch of diodes arranged in a certain way.

The filtering though was a mystery. How do you know what values to use? After gathering quite a few different circuits it seemed everyone was using different values, so who had it right?

The idea is this: use the characteristics of a capacitor to ‘fill in the gaps’ of a rippling DC supply. Remember, we rectified AC, which gave us rippling DC. That ripple will be at a frequency that can be heard by us humans, so we need to reduce that ripple to be inaudible.

Here’s a graphic showing a number of things. Firstly, this is a time-series showing voltage over time for the circuit at the top of the bitmap. Its a simple circuit showing an AC source going through a rectifier. Then the AC signal flows across C1, a capacitor. This graphic is to explain how to calculate the value of C1, and the influence it will have on the green waveform, which is the rippling DC source (post-rectification).

Ripple smoothing calculation

Ripple smoothing calculation

So imagine it like this:

1) The rippling DC source voltage rises to reach about 32 volts. During this time C1 is charging.

2) as the DC source starts to come back down, C1 starts to discharge. This serves to “fill the gap” between the ripples.

The chart is showing, with the different coloured lines, the influence of different values of C1 on the rippling DC.

Here’s a great article on this subject.

A more modern approach.

It seems to me that it is rather than painstaking to install a network of capacitors to perfectly smooth out the rippling DC. Also, transformers are far from perfect, so under load they sag, in terms of voltage. Even if you got all your calculations right, under load it will behave differently.

It is far easier, but not necessarily more efficient (in terms of trees and polar bears), to use a voltage regulator. The 78XX series works very well. You give it more voltage than you require, say 12V, and it does the work to provide you with an almost entirely ripple-free steady 9V. Any excess voltage is ‘given up’ as heat. This is why you might need a heat-sink (and why dolphins and rainbows are destroyed). Here’s a typical circuit using regulators:

AMZ power supply

A typical regulated power supply for guitar pedals

The end result

I came up with a simple circuit that used part of the above circuit to provide 9V and 18V for about 10 pedals. My initial circuit was flawed in that I’d ordered the wrong voltage regulators. They could only handle 100mA. Once we’d connected up all of Mike’s pedals, it would literally cut out. I even connected each one individually to my bench supply so I could measure each ones current draw.

Investigation showed that the regulator was extremely hot, so it became clear that the thermal protection was being tripped. I replaced the 7809V regulators with higher current handling ones and all was well.

Here’s some photographs of that build:

The finished 9V/18V power supply

A very simple decal makes the enclosure look quite spiffy, I think.

Gut shot of 9v/18v power supply

The circuit mounted inside, with all the DC connectors

The final schematic

The final schematic

And the final schematic, with values underneath:

  • D1 – 1N5401
  • C1 – 470uF
  • C8 – 0.1uF
  • D2 – 1N4148
  • IC1 – L7809CP
  • C3 – 10uF
  • R1 – 100R 1Watt
  • C2 – 100uF

 

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Building a Z.Vex Box of Rock on vero-board

0405_Marshall_Amp_630x420Why?

As most guitarists will admit, we’re always looking for a better sound. Some look for new and perhaps innovative sounds. Others, such as myself, want to sound like the players we admire. One classic tone I had never really toyed with is the sound one gets when you crank a JTM45 Marshall. In my opinion it is in my Top 5 sounds. The likes of Clapton, Hendrix, Young (Angus), and many others, started their careers with it. There’s no need for me to recount the origins of the circuit as that’s well documented.

So, you might ask “why not just buy a JTM45?”. Well, one in good condition from the 60’s might set you back 5-10 thousand <local currency units>. A new one, such as those available at Ceriatone go for about $1000….a ‘real’ Marshall? more like $1800.

How

One solution is to approximate the tone in a pedal. And yes, I’ve built way too many overdrive/distortion pedals already, but not one like this. The approach here is to cascade two or more gain stages to ape the design of the JTM45. This has been done may times in plenty of pedals, but a popular one is the Z.Vex Box of Rock. I first heard of this device when it was mentioned by Davy Knowles, who is an excellent blues guitarist. Searching briefly online and I found that the design of the pedal built upon the Super Hard On booster; one of which I built last year. This struck me as a great way to go as I understood that circuit.

Schematic

ZVex Box of Rock schematic

ZVex Box of Rock schematic

Even if you can’t read schematics, you can probably see a pattern repeating itself. There are 4 BS170 transistors arranged as gain stages. They’re chained together and setup in such a way to simulate the characteristics of a tube amplifier. There’s a 4th one (at the bottom right of the schematic) which is the boost section. That will have its own footswitch, so it can be turned on when you “need a bit more”.

I went for a slightly different EQ section. As it stands the BoR just has a simple Muff-style filter. As in, a low-pass filter and a high-pass filter ‘mixed’ together by the tone knob. There’s a great variant that adds a ‘mid scoop’ control, as specified beautifully here by AMZ. It was simple enough that I decided to add it myself.

Layout

I got the veroboard layout from my usual place: Guitar FX Layouts. This guy always does a great job, and is always around to help or explain things. Fantastic!

ZVex Box of Rock - Complete

ZVex Box of Rock – Complete

Build

The build in-progressThe build started off ok, but proved tricky. I quickly realised that I’d done something very wrong as it just sounded very odd. I remembered experiences from previous builds and went back with a fresh printout of the layout, and ticked off each cut, link and solder spot, and made sure the component values were correct. It turned out I had got some cuts in the wrong place. Literally as simple as that. I was careful to use sockets for the BS170s; this meant I was able to leave them out until the last minute so as to not expose them to static shock risk.

Enclosure

Spray and bake

Spray and bake – the black paint hardening under the lights

I went for some custom graphics again. As is typical I couldn’t really think of anything particularly innovative, and ended up calling it “Bed Rock”. This stands to mean two things: 1) This tone is the bed-rock of modern music 2) You can get that tone at low volumes so you can ‘rock’ in your ‘bedroom’. I know, cheesy.

Most of all I wanted to created something with a splash of colour. So many pedals look so very boring. I did the usual flow of finishing the enclosure with enamel based spray paint. This time it was a cheap can of black from Ace Hardware. I was actually going to try something new and bake the enclosure in a toaster oven, but I realised that I was already doing a kind of slow bake with my work-lights. And as I wasn’t in a hurry, I stuck to my usual routine.

For the decal itself, I used a combo of Photoshop and Illustrator to create an image. It was printed on my trusty HP Office ink-jet printer, onto white-backed decal paper; purchased from Small Bear Electronics.

One pleasant discovery was that you can get high-quality fonts for free at sites like FontSpace. Here’s the one I used for the main wording, All Ages.

Almost there!

Almost there!

The finished 'Bed Rock'

The finished ‘Bed Rock’

Demo

I think it came out well. With a Les Paul, it’s ridiculously easy to get that classic AC/DC rhythm tone with everything at 12 o’clock, and with the boost section kicked in you’ve got just that little bit more sustain available for a solo. Even a Strat sounds good. On mild gain settings it really makes single-coils come alive. I ought to do a recording of that too, I suppose. Here’s a demo file of the device.

My setup is the same as usual: Steinberger GM-7SA plugged into an AX84 tube amp, running clean into a 2×12 open-backed cab, with Celestion G12-75T speakers, miced by a Shure SM57 being recorded by an Apple Mac.

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Fitting a 1961 Gibson PAF Humbucker in my Tokai Les Paul

The Tokai LP with its original chrome covered pickups

The victim

The Tokai Les Paul that my wife bought me back on 2005 is a glorious instrument. I have a nice set of guitars; even a “vintage” 1970’s Goldtop, but I always return to my Tokai. It just feels right. The neck is quite fat, and the frets low, but not too low. And the flame maple top underneath a beautifully sprayed cherry-sunburst is simply beautiful.

With all that in mind you’d wonder why I’d ever want to change anything, right? Well, I’m a tinkerer that just cannot leave things alone. Also, I have old bits of guitar hardware laying around and it’s always fun to try new things.  So I decided to take out the stock Tokai humbuckers and fit two pickups that I’ve had laying around for  a very long time. A Seymour Duncan JB (SH-4) and an honest-to-goodness PAF from a 1961 ES-335.

Work begins

I knew in advance the problem was going to be the old PAF. It seems to be quite fragile, and what’s left of the braided wire is very short. Luckily I had some RG-174 left over from building my amplifier, so I grafted some of that onto the old cable.

Old Tokai hum buckers. Look at that curly maple!

But before I could fit the ‘new’ pickups I had to remove the old ones. That proved to be very easy as there’s only two conductors from each pickup, so it took longer to remove the strings and screws than it took to de-solder them.

More luck; I didn’t think I had the right screws to support the PAF in the surround. Gibson pickups from the 60’s use “imperial” threads; Tokai pickups from 2005 use metric. So far so good, but the other pickup…the JB…also uses metric, despite being made in the US. Over the years I have accumulated lots of pieces and parts so it took only 5 minutes of searching in my old parts cabinet and I was rewarded with the appropriate screws. I bet I bought them years ago for the PAF and promptly forgot. The soldering part was trivial. I even replaced the dodgy looking caps with some Mallory 0.022uF ones. Why not? I was already in the guts of the thing.

I am now the proud owner of a Tokai Les Paul with an odd pair of pickups. Now its looks have changed….much more like the one Clapton played in the 60’s.

Here’s an MP3: CLICK HERE

Look at how gorgeous she is:

Job complete...looking cool

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