How Does A Wah-Wah Work?

Way back when electric guitars were still new fangled a few country players found they could add accents and expression to their music by twisting the guitar’s tone control while they played. Although subtle and somewhat tricky to negotiate, this maneuver produced a shift between muted bass and bright treble, adding color and movement to the notes. Read more

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Carvin Legacy VL212 Combo Review

We were more than a bit surprised when this underrated, business-like amp slipped from its cardboard carton. No fluorescent floral Tolex? No trans-dimensional quantum drive? Not even a monkey grip? Steve Vai designed this, didn’t he? Read more

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Vaccaro Groove Jet & X-Ray Guitar Review

If you’ve seen advertisements for Vaccaro’s guitars on the internet or magazines, you may have noted their slightly confrontational slogan: “They’re not for everybody.” This statement, it seems, is absolutely true. The reactions I’ve seen when whipping one of these unorthodox instruments out of my gig bag have ranged from shock (“Where di you get that?”) to covetous (“Awesome! Where can I get one?”).

Brought to you buy the people who created Kramer’s distinctive aluminum and wood-necked guitars in the late Seventies and early Eighties, Vaccaro’s guitars feature daringly designed popular bodies, bold finishes and unique aluminum, maple and ebanol composite necks. The Groove Jet evokes the unholy alliance of a Gibson SG and a satanic dung beetle, and features two Seymour Duncan Custom ’59 humbuckers, a three-way switch pickup selector located on the top horn of the guitar, two volume controls and a master tone control. Our review model was flawlessly finished in a stunning see-through emerald green. The X-Ray, whose sleek, orange sparkle body has a space-age Rickenbacker vibe, boasts two Rio Grande Muy Grande pickups: a humbucker in the bridge and a single coil in the neck position. Both pickups are topped off with the same mother-of-toilet-seat plastic as the pickguard, adding to the instrument’s undeniable ie ne sais quoi. The X-Ray’s control layout is simple yet versatile: a three-way pickup selector, coil-tap switch for the humbucker and single volume and tone controls. The hardware on both guitars (Sperzel locking tuning machines, super-sleek Tune-O-Matic-style bridges and top-notch components) is bullet-proof. The phenolic “I can’t believe it’s not ebony!” fingerboard are smooth and natural feeling, and the well-finished frets provide a sleek, effortless playing surface.

Run through a Bogner Ecstacy head powering a vintage Marshall 4×12 cabinet, both guitars performed admirably well. The Groove Jet’s Duncans are not obnoxiously hot, yet they provide full, articulate, distorted sounds that are both aggressive and musical. Backing off the volume controls allow for dead-on bluesy “in between sounds,” and on clean settings the instrument responds exactly as a two-humbucker contender should. The X-Ray’s Muy Grande pickups (as the name so subtly indicates) have a zingy, refried Texas tone, and when the single coil is combined with the humbuckers in single-coil configuration, they produce extremely hot ‘n’ tasty Fender-like tones. These guitars may look wild and crazy, but their sound and feel are full and old-fashioned goodness.

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How to rate your amplifier speaker cabinet ? - properly hook it up

Why is it that when manufactures rate their stereo amplifiers at say, 40 watts, the back panel will usually read 20×20? Is that really 40 watts? And if I run two 60-watt mono amps through a stereo signal processor, using one amp for each channel, does that make 120 watts? I’m also very confused about matching heads and cabinets. Could you explain the whole ohm thing?

Chad Baker
Irvine California

Everyone has heard the terms “peak” and “RMS” power; they’re the most commonly used power measurements, RMS stands for “Root Mean Square,” and is a mathematical averaging of an amp’s ability to deliver clean, undistorted power. “Peak” generally refers to the maximum power capability of an amp, full blown and distorted. An amp’s peak power is usually just short of twice RMS rating. So, if each channel of your stereo amp is rated at 20 watts RMS, you’ll have a sum total of 40-watts RMS. But, the peak power, depending on the amp’s design, will be around 80-watts or so (combined). These numbers hold true whether you have a single stereo amp or two separate mono amps (60W X 60W = 120W).

Now to the more complex part of your question. Dead German physicist George Simon Ohm’s law is R=E/I (I=Current [amps], E=Electromotive Force [volts] and R=Resistance/Impedance [ohms].) When we flip it around for our guitar amp purpose we get:

(R1)(R2) Impendence of two
———- = speakers in a parallel circuit
R1 + R2

This formula will work for the majority of cabinets. The other type of wiring is called “series,” and is generally found only in the internal circuits of cabinets. If you need to calculate the impedance of a series circuit, just add up the resistance (R1+R2+R3=cab impedance).

Generally, you won’t need to do any heavy math for most amp/cab combinations, because if you are using two matching cabinets in parallel, all you have to do is divide the impedances in two. For example, the impedance of two 16ohm cabinets is 8ohm. But if you get stuck with two mismatched cabinets, let’s say one at 16ohm and the other at 8ohm; you’ll have to use the big formula to arrive at an impedance of 5.33ohm. In this situation, you could set your amplifier to 4ohm without doing any damage, but the 8ohm cabinets will be doing twice the work and be much louder than the 16ohm cabinet—not good for the speakers and a waste of the power-handling capabilities of the 16ohm cab. Its best not use mismatched cabinets. You run the risk of damaging your amp, like Marshall, Hiwatt and Soldano, have speaker jacks wired in parallel with a selector to produce the right impedance from the output transformer. With this type of setup, you simply do the math and plug in. On Fender and Mesa Boogie amps you’ll find one jack labeled 8ohm and, usually, two others, labeled 4ohm. If you have one 8ohm cabinet, plug it into the 8ohm jack; if you have two 8ohm cabinets, plug them into the 4ohm jacks.

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