Four Banger – Four Popular Boosts in One Box

5 08 2008

Greetings, for the past two weeks I have found myself sequestered in a hotel whilst my kitchen has been completely gutted and renovated. Fortunately, my suite is equipped with a large desk which has made an ideal workbench for me to continue my experiments, studies, and builds. Actually, with nothing much else to occupy my time (other than a small commercial sound system repair/install job last week), I’ve been able to get quite a bit of much-needed work done.

Behold, this was built for one of my customers:

Four Boosts in One Box!

Four Boosts in One Box!

It is four popular boost circuits put together in one box with toggle to turn each individual one on and off. The boost which have been included are as follows and are wired in the following order: classic Rangemaster Germanium Treble Booster, a clean opamp boost of my own design, a ZVex-designed Super Hard-On MOSFET booster, and Jack Orman’s MiniBooster Mu-amp JFET boost. Individually, these are all great boosters, but when together like this, a whole pallet of different colors is available to the artist who wants options. The most ingenious part is that the toggles allow the ability to cascade several boosters together simultaneously for a wide range of interesting overdrive and fuzz flavors. The combination of the Rangemaster, SHO, and MiniBooster on simultaneously has to be heard to be believed! I may design a fuzz that’s based on that topology because it really brings some new things to the game, timbre-wise.

Here’s a look inside:

Guts!

Guts!

This one was all hand-wired on perf board. If I sell any more of these, I will be inclined to design a printed circuit board for it. Hand-wiring one effect is fine, but when you need to do several of them and want them to be consistent, it certainly isn’t recommended! I almost always do custom one-offs on perf board like this, but when something is more of a “production” model, a PCB is almost always a necessity for the sake of consistency and quality assurance.

There are some good tricks in this one; a MAX1044 charge pump chip is used to derive a negative supply from the standard 9v battery. This allows me to have a true bipolar supply for the opamp circuit (for maximum clean headroom) and it also gives me the luxury of being able to wire the Rangemaster’s PNP transistor “correctly” with a negative rail being referenced to ground. Some people (*cough* Robert Keeley *cough*) build Rangemasters with the circuit wired “upside-down” so that you don’t need the correct negative supply rail; they use ground to represent the negative rail in reference to the positive pressure coming from the battery. This is an okay trick, but it’s a compromise and isn’t ideal and can lead to stability problems and other unpleasant possibilities. Using the correct negative supply allows it to live quite happily alongside the other boosts in the same box and it illustrates the no-compromise approach I like to take to these kinds of circuits. Another compromise I avoided was the use of input pull-down resistors. I wanted the customer to experience the perfect sound of these boosts without the impedance mangling that can happen from the injudicious use of pull-downs. These extra resistors are used to keep the bypass switch from making a popping sound due to coupling capacitor discharge. I’ve found that with a particular wiring scheme which keeps the circuit input grounded while bypassed, this popping is minimized or completely inaudible without the use of the extra resistors.

I am quite pleased with how this project turned out. I was even able to get a satisfactory “rustic” look for the labeling using rubber stamps and “StazOn” brand solvent-based ink. If anyone is interested in having a custom booster such as this built for you, please contact me at: solgrind [at] lavabit.com, or Gmail users may contact me at: solgrind78 [at] gmail.com
I consider my prices very reasonable, and if you’d like a Four Banger such as the one in this article, I am asking only $100. (The current price a standard Four Banger is $120. Please see update post). Any other effect you may be interested in would likely be similarly priced and of course would depend on what you are wanting. I consider my work primarily custom and what I can build is sometimes limited by the availability of certain parts (i.e. reasonable quality Germanium transistors are becoming rare).

Anyone interested in building something like this for themselves, can find info about the Jack Orman’s MiniBooster at http://www.muzique.com, the ZVex SHO at http://freestompboxes.org and http://www.diystompboxes.com, a really good article about building the Dallas Rangemaster can be found at http://www.geofex.com, and the opamp boost is a fairly standard generic circuit you can find the basis of in any good electronics text book.

-M.C.

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One response

20 10 2008
Richey

$100??? I WANT ONE!!! Where do I send the $$??

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