Mesa Boogie Roadster Guitar Amplifier Review

April 8, 2013 by · Leave a Comment 

Mesa Boogie Roadster

The almighty Mesa Boogie Roadster is a great sounding and versatile amp that is designed with the plug-in-and-play guitarist in mind. It is a brother to the Road King amp and is basically the same as the RK minus Mesa’s Progressive Linkage technology and some other back-panel features that some feel a player needs an advanced engineering degree to operate.

The Roadster gives less tech-friendly players a number of foot-switchable options to craft their tones with, without the anxiety of tons of power amp features they don’t understand. The Roadster’s channels one and two give up classic clean tones that can be duplicated across both channels for rhythm and lead applications. They also have TWEED and BRIT modes that work with the mid frequencies to get classic American blues and British rock sounds from clean to clipped. These two channels would make a great sounding and versatile amp all by themselves. Channels three and four offer players all the legendary tones found in Mesa’s Dual Rectifier Solo heads and contain all flavors of gain from mild to wild. Again, the sounds can be cloned across the channels for ultimate tonal control. Read more

Field Guide to Guitar Amplifier Tubes – Everything You Need To Know

March 27, 2013 by · 3 Comments 

Guitar amplifier valve tubesWhat is a vacuum tube? — If the link between a light bulb and a raging Marshall stack doesn’t seem obvious, take a glance at those vacuum tubes glowing inside your amp. And then pay your respects to Thomas Edison, the Wizard of Menlo Park, New Jersey.

Edison produced an incandescent light bulb in the late 1870s by feeding an electric current to a filament until it burned bright red. He then sheathed the filament in a glass bulb and extracted the oxygen, thus creating a vacuum to prevent the filament from burning up.

During further experiments in 1883, Edison detected electrons flowing from the filament, through the vacuum and over to a metal plate he had placed inside the bulb. This discovery, named the Edison Effect, remained a minor phenomenon until another scientist, John Fleming, found that these electrons could be used to detect radio waves and convert them into electricity. Fleming added a second metal element to the bulb, thereby creating the first diode, or—to use a name more familiar to guitarists—rectifier. In 1906, inventor Lee de Forest added a third element to the bulb and found that the resulting triode could be used as both a switch and an amplifier. Today, the vacuum tube has evolved to include a complex assembly of plates, grids and heating elements that produce a more efficient part. Read more

Tube vs Solid State Amplifiers – Which is Better?

January 9, 2013 by · 5 Comments 

Tube Amps vs. Solid State AmpsThere are a few central debates that continually rage in this thing of ours, topics that never seem to get exhausted during online forum or real time arguing: Gibson vs. Fender, Fender vs. Marshall, Ginger vs. Mary Ann, Bud vs. Miller, and, most importantly, tube amps vs. solid state amps. These are the things guitarists think about. Now, I can’t help you decide to play a Les Paul over a Strat or who to spend Read more

How to Listen to and Care for Your Amp When It’s Sick

November 3, 2011 by · Leave a Comment 

Fender Vibro KingGuitar amps are, no matter how you cut it, black boxes. You may think you have control over them, but when it gets down to it, you can’t really see inside the black box, and even if you could, there aren’t any moving parts. Electricity is largely non-mechanical. Or in other words, magic. And when the magic stops, most people think all they can do is resort to prayer. Or an amp technician.

When your amp isn’t performing up to snuff, there’s still a lot you can do without having an EE degree, or even knowing how to operate test equipment. Here are some holistic approaches—and solutions—you can try yourself, as I did when my tube amp went on the fritz. Warning: Some of the following procedures involve messing around with the components of the amp, so be careful. Electricity can kill you. Proceed at your own risk. Read more

Basic Electric Guitar Circuits: Potentiometers and Tone Capacitors

September 15, 2011 by · Leave a Comment 

What is a Potentiometer?

Potentiometers, or “pots” for short, are used for volume and tone control in electric guitars.  They allow us to alter the electrical resistance in a circuit at the turn of a knob.

Potentiometers and Tone Capacitors

It’s useful to know the fundamental relationship between voltage, current and resistance known as Ohm’s Law when understanding how electric guitar circuits work.  The guitar pickups provide the voltage and current source, while the potentiometers provide the resistance.  From Ohm’s Law we can see how increasing resistance decreases the flow of current through a circuit, while decreasing the resistance increases the current flow.  If two circuit paths are provided from a common voltage source, more current will flow through the path of least resistance.
Potentiometers and Tone Capacitors

We can visualize the operation of a potentiometer from the drawing above.  Imagine a resistive track connected from terminal 1 to 3 of the pot.  Terminal 2 is connected to a wiper that sweeps along the resistive track when the potentiometer shaft is rotated from 0° to 300°.  This changes the resistance from terminals 1 to 2 and 2 to 3 simultaneously, while the resistance from terminal 1 to 3 remains the same.  As the resistance from terminal 1 to 2 increases, the resistance from terminal 2 to 3 decreases, and vice-versa.

Tone Control:  Variable Resistors & Tone Capacitors

Tone pots are connected using only terminals 1 and 2 for use as a variable resistor whose resistance increases with a clockwise shaft rotation.  The tone pot works in conjunction with the tone capacitor (“cap”) to serve as an adjustable high frequency drain for the signal produced by the pickups.  The tone pot’s resistance is the same for all signal frequencies; however, the capacitor has AC impedance which varies depending on both the signal frequency and the value of capacitance as shown in the equation below.  High frequencies see less impedance from the same capacitor than low frequencies.  The table below shows impedance calculations for three of the most common tone cap values at a low frequency (100 Hz) and a high frequency (5 kHz).

Potentiometers and Tone Capacitors

When the tone pot is set to its maximum resistance (e.g. 250k?), all of the frequencies (low and high) have a relatively high path of resistance to ground.  As we reduce the resistance of the tone pot to 0?, the impedance of the capacitor has more of an impact and we gradually lose more high frequencies to ground through the tone circuit.  If we use a higher value capacitor, we lose more high frequencies and get a darker, fatter sound than if we use a lower value.

Volume Control:  Variable Voltage Dividers

Volume pots are connected using all three terminals in a way that provides a variable voltage divider for the signal from the pickups.  The voltage produced by the pickups (input voltage) is connected between the volume pot terminals 1 and 3, while the guitar’s output jack (output voltage) is connected between terminals 1 and 2.  From the voltage divider equation below we can see that if R1 is 0? and R2 is 250k?, then the output voltage will be equal to the input voltage (full volume).  If R1 is 250k? and R2 is 0?, then the output voltage will be zero (no sound).

Potentiometers and Tone Capacitors

Potentiometer Taper

The taper of a potentiometer indicates how the output to input voltage ratio will change with respect to the shaft rotation.  The two taper curves below are examples of the two most common guitar pot tapers as they would be seen on a manufacturer’s data sheet.  The rotational travel refers to turning the potentiometer shaft clockwise from 0° to 300° as in the previous visual representation drawing.
Potentiometers and Tone Capacitors

How do you know when to use an audio or linear taper pot?

It’s really a matter of personal taste when it comes to volume control.  Notice how the rate of change is much more dramatic on the audio taper pot when traveling back from 100% to 50% rotation.  This means that the same amount of rotation would give you a more intense volume swell effect with an audio taper than with a linear taper.  Using a linear taper volume pot would give you a more gradual change in volume which might feel like you have more fine control with which to ease back the volume level.

For tone control, it’s basically standard practice to use an audio taper.  The effect of the tone circuit is not very noticeable until the resistance gets pretty low and you can get there quicker with an audio taper.

How do you know what value of potentiometer to use?

The actual value of the pot itself does not affect the input to output voltage ratio, but it does alter the peak frequency of the pickup.  If you want a brighter sound from your pickups, use a pot with a larger total resistance.  If you want a darker sound, use a smaller total resistance.  In general, 250K pots are used with single-coil pickups and 500K pots are used with humbucking pickups.

Specialized Pots

Potentiometers are used in all types of electronic products so it’s a good idea to look for potentiometers specifically designed to be used in electric guitars.  If you do a lot of volume swells, you’ll want to make sure the rotational torque of the shaft feels good to you and most pots designed specifically for guitar will have taken this into account.  When you start looking for guitar specific pots, you’ll also find specialty pots like push-pull pots, no-load pots and blend pots which are all great for getting creative and customizing your guitar once you understand how basic electric guitar circuits work.

Kurt Prange (BSEE) is the Sales Engineer for Amplified Parts ( in Tempe, Arizona, United States.  Kurt began playing guitar at the age of nine in Kalamazoo, Michigan.  He is a guitar DIY’er and tube amp designer who enjoys helping other musicians along in the endless pursuit of tone.

Ampeg GVT Amps, ESP 7 and 8 String Guitars Introduced

August 18, 2011 by · Leave a Comment 

Ampeg GVT NAMM’s Summer Show is officially in the books, giving wholesalers and musicians a whole new list of the stuff that dreams are made of, including a new lineup of 7- and 8-string guitars from ESP, as well as another Asian Invasion, the new GVT Series amplifier line from an expatriate veteran, Ampeg. Read more

Finding the Right Guitar Amplifier – Amp Wattage

March 3, 2011 by · Leave a Comment 

Marshall Half Stack Hybrid

I have a Pignose Hog 20, and every time I jam with other players, the drummers drown me out. I’m 15 years old and don’t have a lot of money. I’m wondering what size amp I should by so that I can be heard above the drums without the amp distorting. Also, how are amplifier wattage ratings determined?


Let’s tackle your last question first Johnny, since this will help us answer your question about what size amp you should buy. Amplifier watt ratings are determined by a calculation called “root mean square,” or RMS. It simple terms, RMS is a measurement of the average, or “effective,” voltage your amp can produce continuously under normal playing conditions without clipping (what happens when you crank up your amp and it starts to distort). Some manufactures give their amps a power rating that’s closer to the peak output—that is, the highest wattage that the amp is capable of producing. This isn’t a very accurate way to measure wattage, because amps don’t operate (or shouldn’t be operated) at peak levels for an extended period of time. If you were to operate an amp at its peak output, I assure you, not only would your tone suffer but the amp itself, including its speaker, would burn out very quickly.

Let’s look at an example. If you have a 50-watt amp and it starts to distort, or “clip” as the output approaches 35-watts, is it a 50-watt amp or a 35-watt amp? To put it another way, if you want an amp that can produce 50-watts of continuous power, don’t buy an amp that has a peak power of 50-watts, because the amp will start to distort well before it reaches the 50-watt mark. Read more

Rivera Sedona Guitar Amplifier Review

March 1, 2011 by · Leave a Comment 

Rivera Sedona Doyle DykesRivera’s Sedona is essentially two amps in a single package, but before you hit the next button on this page thinking that it’s just another two-channel combo, you should be aware that it is the only amp we know of that combines and electric guitar amp and an acoustic guitar amp in one. This is welcomed if you frequently double on electric and acoustic instruments, or if you have a hybrid electric/acoustic axe like a Parker Fly or Hamer Duotone and you’re sick of hauling several amps to a gig just to sound convincing.

Musician's Friend

The Sedona was designed for Nashville fingerpicker Doyle Dykes, who wanted an amp that he could plug both his Tele and his Taylor into and have each sound equally outstanding. Featuring two fully independent channels that are respectively voiced to deliver optimal electric (channel 1) and acoustic tones (channel 2), the Sedona also features an ingenious speaker system consisting of a 12-inch JBL full-range speaker and a 5-inch high-frequency Electro-Voiced driver that can be set to switch on only when you select channel 2. The EV tweeter provides an enhanced treble response that perfectly complements the extended frequency range of an acoustic guitar, providing rich, natural-sounding tone.

Covered in brown Tolex and featuring a matching brown grille and classy leather handle, the Sedona looks right at home in places where the clientele is more likely to sip cappuccinos than Coors. But don’t be fooled by its gentrified appearance as the Sedona can pump out enough volume and distortion to shatter earthenware mug.

Rivera didn’t skimp when tic amt to supplying features for this amp. Each channel comes with a full complement of tone and gain controls (bass, middle, treble, volume and master). Both channels share a single set of presence and reverb controls. Several of the controls are also pull switches that provide additional functions: channel 1’s pull functions include channel select (volume) and boost (master), channel 2’s pull functions are bright (treble) notch (middle), and Ninja boost (master), which lets you overdrive the amp’s output section. The front panel also boasts a pair of level and frequency controls for the amp’s anti-feedback equalizer, which is active only when channel 2 is selected. These controls not only help you eliminate feedback, they also help enhance the sound of acoustic instruments plugged into the amp by giving you even greater control of the instrument’s frequency response. Read more

Kendrick 2210 Combo Amplifier

March 1, 2011 by · 1 Comment 

Boutique Guitar Amps Fender KendrickNot only is the Kendrick 2210 the best-sounding, best-looking and best-built Fender-style amp I’ve run across it also encapsulates two prevailing trends in musical equipment: a craving for the lost quality attributed to anything “vintage”, and an appreciation for small production-run, handmade gear. Read more

VHT Sig:X Amplifier Head Review

February 24, 2011 by · Leave a Comment 

VHT Sig:X Amplifier Head ReviewNEARLY 20 YEARS AGO, VHT paved the road for the modern “super amp” category by combining a high-power output stage with three fully independent channels and an advanced switching system—along with a host of other groundbreaking features. The Sig:X extends that legacy with a truckload of fine-tuning features and enhanced versatility Read more

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