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Guitar tube valve amplifier

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WATCH RELATED VIDEO: Best Tube Guitar Amps For Home Use

How to Diagnose Your Amps Bad Tube


Put your hand in front of an empty electric socket, and you won't get a shock— because electrons just don't fly through space, right? Well … they will under the right conditions—like inside a vacuum tube. While this stuff may be daunting to some of you, take heart—this is century-old technology. The basic concepts really are not too difficult to grasp. We'll discuss amplifier circuits by looking at my absolute favorite small amp, a s Vox AC4.

While it's small and simple, an AC4 actually is not the simplest guitar amp out there. Unlike Fender's earliest tweed Champs, the AC4 has a tone control and tremolo, which gives us a bit more to talk about. But before we get started, let's make it clear that this article is not in any way encouraging or equipping you to open up the back of your amp and start poking around. Make no mistake: Amplifier circuits, even when unplugged, contain voltages that can kill you.

And if you're an amp tech, please excuse any oversimplification in the discussion—this is a primer for general consumption, not a compendium of possible exceptions and anomalous phenomena.

First, let's talk about some basic principles of electricity. An electron—the heartbeat of electric energy—is a negatively charged subatomic particle. In a vacuum i. Experiments conducted well over a century ago demonstrated that electrons will not only fly through space, but they can also be controlled.

Scientists showed that, in a vacuum, electrons flowing from a heated metal element—the cathode—and being pulled toward a positively charged element—the anode—can be deflected by a magnetic field.

A Vox AC4, like many amps, is designed to make the power tube's cathode slightly positive—a state that is commonly referred to in the guitar universe as cathode biased. Other amps, instead, put a negative charge on the power tube's grid. That's called fixed bias, and it has a similar effect. Either method causes electrons to stay put on the cathode until needed. Learn how to control that magnetic field accurately and, as RCA did, you can display an image of Felix the Cat on a phosphorescent surface at the far end of the tube.

In guitar amps, we're not that interested in displaying images with our tubes, but we're still very interested in controlling those electrons—and we can use a guitar to do it. Picture this: In the center of a tube's glass envelope is a cathode. It carries just a slight positive charge, and it's ready to release a gazillion electrons. It's especially ready if it's been heated. Surrounding the cathode is the anode—although in the guitar universe we typically call it the plate.

The plate carries a high positive charge that's ready to pull those negative electrons toward it. To the highly positive plate, the cathode's slight positive charge still makes the cathode seem negative we'll talk more about this slight positive charge later. If you place these two elements in a vacuum and power them up, electrons will fly relentlessly toward the plate.

When you add a third element—the grid—between the two, you can control the flow of electrons. And when you position the grid close to the cathode and connect the grid to the relatively tiny voltages coming from your guitar pickups, something interesting happens: The tiny signal unleashes a flood of electrons, allowing them to fly freely to the plate.

That rush of electrons from the cathode to the plate mirrors the signal from the guitar, amplifying its signal many times over. Okay, so let's get back to that earlier mention of the slight positive charge. The reason we want the cathode to carry a slight positive charge is that it makes the grid, with no charge yet applied, seem negative.

Voltages are relative. And while opposites attract, like charges repel. The apparently negative grid close to the cathode will keep those negatively charged electrons in place until the guitar signal is ready to swing the grid positive to release them. One other useful electron-related fact to know is the difference between voltage and current. Think of current as the amount of water flowing through a pipe. More current means more water being delivered.

Voltage, on the other hand, is like water pressure— it's the force behind that water. Increase the voltage pressure and you'll increase the current amount of flow. A resistor acts like a constriction in the pipe, with more resistance being analogous to a tighter constriction. So it follows that placing a different resistor in a circuit will affect both the voltage and the current. What actually goes on inside a guitar amplifier is obviously a bit more complex than just the flow of electrons in tubes, though.

Next we'll do a quick overview of the additional parts involved, followed by more detailed, part-by-part descriptions. The first and largest component in an amp circuit, aside from the speaker, is the power transformer. It supplies electricity to the circuit, converting AC voltage from the wall to proper AC voltages for the amp.

AC aka alternating current is a sine wave of electricity—an alternating positive and negative voltage coming from our electric sockets at volts, 60 sine waves a second in the U. These operating voltages vary around the world.

Standard voltage can be , , or volts, at 50 or 60 cycles per second. The AC4 is designed to provide the plates of the latter three tubes with a different DC voltage that's appropriate for that tube.

The AC4's power transformer elevates the AC volts to volts AC, and then sends that voltage on to the rectifier tube, the first tube in the circuit. The rectifier tube's job is to convert AC voltage to DC aka direct current—a steady positive voltage rather than a sine wave. The power transformer's other job is to supply low AC voltage to the filaments the heaters inside every tube in the amp—that's what gets the cathodes hot.

The filaments in the AC4's tubes all work off of 6. Converting the power transformer's AC voltage to DC voltage coming from it isn't steady, it's more of a ripple. Filter capacitors—the large, cylindrically shaped components that come next in the circuit—help smooth out the ripples in the DC voltage. Filter capacitors are similar in construction to batteries in that they store a charge—a potentially lethal charge—even after the amp is unplugged.

This is why you should never poke around inside an amp unless you've been trained to safely discharge the caps. The high and relatively steady DC voltage dispensed by filter capacitors goes to the tube plates—the elements that need that high, positive, electron-attracting charge. The amount of voltage on a tube's plate is determined by the voltage coming off the filter caps, and also by resistors positioned along the DC line.

With a high DC voltage, the plates are ready to start pulling electrons. To the uninitiated, circuit schematics can look like a rat's nest of wires and components arranged in a way that saves space on paper—but that also needs to be mentally untangled in order to truly understand the circuit. Here is a s Vox AC4 schematic, rearranged and color-coded to help you decipher what's going on.

Note: AC and DC voltages can coexist on the same wire. In a guitar amp, the AC guitar signal is imposed on top of the high DC voltages. Fortunately, that AC signal can be separated: Capacitors in the circuit block DC voltages but allow the AC guitar signal to get through. We all know your guitar's signal comes from your pickups, but to understand the amplified signal, let's start at electrical ground. In practice, ground in a guitar amp means a connection to the chassis.

In the AC4 schematic, the ground connections look like upside-down Christmas trees. Electrons flowing through a tube originate from ground. The cathodes of the EF86 and the EL84 each have a resistor attached to ground. This creates the small DC voltage on their cathodes to prevent the electrons from flowing. When the guitar signal reaches the grid, the electrons then flow. However, the cathode resistor alone would also affect electron flow when the guitar is played.

A bypass capacitor is put in parallel with the resistor to increase gain and allow AC electrons to effortlessly get through. The electrons released by the guitar signal flow from ground to the EL86 cathode, then to the plate, through a. At the EL84, a similar electron flow takes place, but this time it's more powerful.

Enough electrons will travel from the EL84's plate to the output transformer to drive the speaker. Here we see a view of the AC4's chassis with the back panel removed above , and with the chassis removed from the amp below —a design that makes it a bit of a chore to try out tubes from various manufacturers, both old and new stock. The electrons don't stop at the output transformer, though.

If you look at the schematic, you'll note that they pass through it and cycle back to ground. In a way, you can think of an amplifier as an electron circulator whose ultimate goal is to send electrons through the output transformer. Our job as guitarists is simply to get those electrons to do that in tune and with reasonable timing. You're probably familiar with the mix up in terminology between "vibrato" and "tremolo.

That oscillating voltage is connected to the cathode of the EF86 tube, which affects the bias. Think of it as sending a very low-sound signal to the EF86's cathode—maybe 2—10 Hz cycles per second. These frequencies are way too low for the human ear to detect, but they do affect electron flow in the EF86 from 2 to 10 times per second.

Now that we've got our quick overview of how an amp works out of the way, let's get into some more detailed descriptions, component by component. The power transformer is the amp's larger transformer. The transformer also supplies 6. Capacitors are shown in the schematic as two parallel lines perpendicular to the wiring. In some schematics, one of the lines may be curved.

Filter capacitors are large metal cylinders that, like batteries, hold a charge—even long after the amp has been unplugged. Unlike batteries for household items like flashlights and smoke detectors, they hold potentially lethal voltages.

These are why you don't mess around inside your amp unless you know how to do so safely. The rectifier tube's purpose is to convert the AC voltage a sine wave into a constant DC voltage to power the tubes. The rectifier tube does a good but not perfect job. What emerges is actually a ripple-like DC voltage, so the filter capacitors help reduce the ripple by storing and releasing high voltages.


Valve amplifier

Besides the guitar itself, a decent guitar amp is one of the most significant purchase a guitarist will make. Indeed, an amp is arguably more important to your overall tone than the guitar! Your first 'proper' amp is likely to be based on something that your heroes play, but you'll soon end up wanting something that better fits your own playing style. Whether you use overdrive pedals to provide your gain, or you're looking for your amp to provide full bore distortion on its own, the amp you go for will determine the overall character your audience hears out front. There's a dizzying array of amps on the market, so you need to do some thorough research before pulling the trigger to figure out what's right for you. We've listed them in price order to make your life a little easier, and we've even found the best prices for 'em, too! Are you looking for a great deal on the best guitar amps this Black Friday?

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The best guitar amps to buy in 2021: 15 best tube amplifiers


JavaScript seems to be disabled in your browser. For the best experience on our site, be sure to turn on Javascript in your browser. Capable of truly otherworldly tones, some of the most revolutionary guitar riffs in history have been sent firing through an iconic amp head. These inconspicuous boxes have helped to define an entire era of rock'n'roll, with guitar legends utilising their ferocious power to make their cabinets sing. Complete your stack with our magnificent range of Marshall , Blackstar , Orange and more. Showing 18 out of There are some different types of amplifier heads that you should be aware of before buying - Valve or Tube , Solid State, Modelling, and Hybrid. Each of these types offers something different and might suit your playing style more than another type - click here to read our Guitar Amp Buying Guide or take a look at our 20 Favourite Practice Amps for more information. Many people opt for a true-valve head to take advantage of the sweet overdriven sounds that they're renowned for when cranked to the perfect level. Higher wattage valve amp heads will have more clean headroom - this means that the sweet-spot will occur at a higher volume level than it would with a lower wattage amplifier.

Guitar Valve Amplifiers

guitar tube valve amplifier

We build a limited portfolio of hand wired amplifiers inspired by the most sought after vintage amps in history. We are passionate about music and helping you find and create your sound, inspired by time tested amplifier circuits and the best American Made parts available. ValveTrain Hand wired, boutique amplifiers at production prices! Road worthy and dripping with tone…. ValveTrain combo cabinets are solid pine or baltic birch plywood for true Old School tone.

The sound of a valve amp cranked nice and loud is synonymous with rock and guitar heritage. Valve technology was predominately found in televisions and radios from the mid to the late 20 th Century, transistor technology advanced and took its place.

Valve types explained


Here we want to look at the differences between the two main types of electric guitar amps, as well as the advantages and disadvantages of each. On a technical level, the difference between the two types of amps is very simple: tube amps use vacuum tubes to amplify a guitar signal, while solid state amps use electronics to provide amplification. A good way to put it, however, comes from our studio glossary, which defines warm as a sound that is spacious with a good bass and mids response. This warm sound is particularly desirable when those vacuum tubes are overloaded — resulting in a warm distortion sound known as overdrive Of course, there are innumerable overdrive pedals on the market that attempt to replicate this sound. The sound of solid state amps depends largely on the exact circuitry of the amp. And though they are often seen by many guitarists as inferior, they have their own advantages that many guitarists desire.

Best Tube Amps 2021: Top Choices from Fender, Marshall, MESA/Boogie and More

A true anolog sound. Sometimes known as tube amps, guitar valve amps use valves in any or all the stages of amplification. Showing 40 of products. Guitar Valve Amplifiers. Read more A true anolog sound. Read less. Sort by. Head, Cab or Combo?

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Class B designs are much less subject to wear, and also maintain a cleaner signal through most of the path - they are ultimately more flexible. Mesa-Boogie valve amps, regarded as among the most advanced modern designs, combine the best of Class A and B circuitry in various ways, which are often user-switchable for maximum flexibility. Modern heads and combos generally have a similar array of features. This is usually placed between the preamp and power amp, although some amps include flexible routing options, for example allowing the FX loop to be assigned to one channel but not the other. Other effects such as delay and wah-wah can be used in either configuration according to taste. As a general indication though, many loud combos are rated at 50 or 60 Watts, and heads rated at W have a little more power for comfortably driving four or even eight speakers.

Sound City All valve guitar or bass amp In rude health Previous service and capacitor upgrades Fitted with JJ valves This is a b so has lower bass response than a L But also has a brilliant input which can go to way more treble than you.

Cort uses cookies to improve your experience on our website. You can read more about our Privacy Policy. You can change your preferences at any time. Provide your name and email below, and you will be the first to know when the product becomes available in your area. You reserve the right to not agree to Cor-Tek Corp's usage of your personal information for minimal servicing purposes and, should you not agree to this usage, the aforementioned services will not be rendered. The guitar amplifiers with a tube circuit that first unveiled in the s truly bloomed in the s thus opening a new chapter for electric guitar music.

Guitar amps are, after the guitar itself, the biggest factor to consider when creating your electric guitar sound. Amplifiers play a huge part - some would say the biggest part - in the production of tone and there are a vast array of makes, models and variations on offer to get you the sound you dream of. There are many types of guitar amplifier to choose from based on your taste and needs.




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  1. Waldrom

    Many thanks for the information, now I will not admit such a mistake.