Glossary of relevant terms:

[guitar007]

This is great stuff, guys! Keep it comin'!

[curtg]

Clean: The tone a guitar and amplifier creates when not overdriven into distortion. A true, amplified reproduction of the original signal.

That's definitely a term we take for granted, but non-musician, non-tech types hear and look at you funny. You know, that look your dog makes when he hears you make a funny noise?

[5150loveeddie]

Vactrol - an optoisolator device used for channel switching in many modern amplifiers, such as Soldano and Mesa. It is a single package combining an LED and a photoresistor, which changes resistance from very high (essentially an open circuit) to very low (essentially a short circuit) as the current through the LED is turned on and off. It is used as a substitute for relays, to avoid the "clicks" and "pops" that can occur when they are used for channel switching.

[5150loveeddie]

Single-ended - The term "single-ended", or SE, is given to an amplifier output stage configuration whose output transformer primary is not center-tapped. It has only two connections, one of which goes to the power supply, the other to the plate of the power tube. Tubes can also be paralleled for more power as in a push-pull stage, resulting in what is called "parallel single-ended" operation, or PSE. A single ended stage for guitar amplification is always biased class A. Old Fender Champs are a good example of a single-ended guitar amplifier. Higher power amplifiers are usually push-pull instead of single-ended, which allows higher efficiency and better frequency response with a smaller output transformer. Output transformers for single-ended amplifiers require an air gap to avoid saturation of the core due to the offset DC current in the transformer. This air gap greatly reduces the primary inductance. so the core must be made larger and the number of turns must be increased to obtain good low frequency response. A push-pull output transformer has no offset DC current flowing in the primary, because the DC bias current flows in opposite directions on each side of the primary, so it doesn't need an air gap, and can be made smaller. Single-ended output stages do not have the inherent even-harmonic cancellation and power supply rejection that push-pull output stages have, so the output tone is quite different, and the DC plate supply must be better filtered in order to keep the hum to a low level.

[5150loveeddie]

Resonance - a control on a guitar amplifier that boosts the lower frequencies at or below the normal bass control range for added low-end, also called "depth" or other names. This control is usually a shelving type of equalizer, and is normally implemented as a highpass filter inside the global negative feedback loop. By decreasing the amount of low frequencies that are fed back, the low frequencies at the output of the amplifier are boosted. Resonance is also the term given to an electronic circuit that contains both capacitive and inductive elements - there is a "resonant" point where the capacitive reactance equals the inductive reactance. Depending upon whether the elements are in series or parallel, this will result in a maximum voltage and maximum impedance across the elements (parallel resonance) or maximum current and minimum impedance through the elements (series resonance). If the circuit has resistance, either across the parallel resonant circuit or in series with the series resonant circuit, the maximum peak will be limited, and the bandwidth of the resonance will be broader. The relative "sharpness" of the resonant circuit is called the "Q", or "quality" factor. See the definition of "Q" for more details.

[5150loveeddie]

Ohm's law - the fundamental relationship between voltage, current, and resistance. It is usually stated as: E = I*R, or V=I*R, where E or V = voltage (in volts. E stands for "electromotive force" which is the same thing as voltage), and I = current (in amps), and R = resistance (in ohms). The equation can be manipulated to find any one of the three if the other two are known. For instance, if you know the voltage across a resistor, and the current through it, you can calculate the resistance by rearranging the equation to solve for R as follows: R = E/I. Likewise, if you know the resistance and the voltage drop across it, you can calculate the current through the resistor as I = E/R.

A related equation is used to calculate power in a circuit: P = E*I, where P = power (in watts), E = voltage (in volts), and I = current (in amps). For example, if you measure 20V RMS and 2.5A into a load, the power delivered to the load is: P = 20*2.5 = 50W. This equation can also be rearranged to solve for the other two quantities as follows: P = E*I, E = P/I, and I = P/E. You can also combine the power equation with the first Ohm's law equation to derive a set of new equations. Since E = I*R, you can substitute I*R for E in the power equation to obtain: P = (I*R)*I, or P = I2R. You can also find P if you know only E and R by substituting I=E/R into the power equation to obtain: P = E*(E/R), or P = E2/R. These two equations can also be rearranged to solve for any one of the three variables if the other two are known. For example, if you have an amplifier putting out 50W into an 8 ohm load, the voltage across the load will be: E = sqrt(P*R) = sqrt(50*8) = 20V RMS.

[5150loveeddie]

Attenuator - (a) a passive network that is used to reduce the voltage or power of a signal. Typically, this is accomplished with two resistors, one in series with the signal and another from the output of the first resistor to ground. This network attenuates the signal by an amount dependent upon the ratio of the two resistor values, and is sometimes called a "resistive divider" when used with small signals, such as interstage coupling between tube stages in an amplifier. When used to reduce power levels instead of small-signal applications, it is commonly called an "L-pad", or an "L-pad matched in the direction of the series arm" (because it matches impedances in one direction only). The L-pad can also be built with a shunt resistor to ground from the output and a series resistor in series with the output after the shunt to ground (this is commonly called an "L-pad matched in the direction of the shunt arm"). There are other variations of attenuators, including the "T", "PI", and "ladder" configurations and others.
(b) A passive device used to reduce the volume of an amplifier. It goes between the amplifier and the speakers, allowing a non-master volume amplifier to be cranked up to full power without being overly loud, in order to get the desired overdrive tone from the amplifier. Note: there is another class of device on the market now, which uses a passive load followed by an active amplifier (which has a maximum gain of one). This device functions in a manner similar to an attenuator in that it reduces the signal level to the speaker while allowing the amplifier to run at full power. However, it is really a "reamp" device, with the main discernable difference being that it requires a source of power to operate (via the AC mains). These devices should be referred to as "active attenuators" to avoid confusion with the standard passive attenuators on the market

[5150loveeddie]

Crossover distortion - Crossover distortion is the term given to a type of distortion that occurs in push-pull class AB or class B amplifiers. It happens during the time that one side of the output stage shuts off, and the other turns on. Depending upon the bias point, there is a small amount of time where both tubes are in very non-linear portions of their operating curves, or even cut off entirely, and this "kink" in the transfer curves results in a distortion, or notch, at the zero crossing point of the reconstructed waveform.

[5150loveeddie]

Impedance - a complex quantity containing both a resistance and a reactance. The symbol for impedance is "Z", and the unit of impedance is the ohm. Z = R + jX, where R is the resistance, and X is the reactance of the circuit, and j is the complex, or imaginary, operator, indicating multiplication by the square root of -1. Inductive reactances have positive imaginary components, and capacitive reactances have negative imaginary components. For example, an inductor of 1mH with a resistance of 8 ohms would have an impedance of (8 + j6.3) ohms at 1000 Hz. Since an impedance is a complex number, it has both a magnitude and a phase. Typically, when discussing amplifiers or speakers, impedances are referred to as the magnitude of the complex number, instead of the rectangular form as given in the definition. The magnitude of the (8+j6.3) example is 10.2 ohms, as calculated by the square root of the sum of the squares of the real and imaginary parts (the "length" of the resulting vector). The concept of imaginary numbers can be a bit confusing to those who haven't encountered it before. If you are interested in finding out more about this, check out a textbook on introductory circuit analysis, as they usually have a good treatment of the subject.

[5150loveeddie]

choke stuff.....

Inductance - the "size"of an inductor, not the actual physical size, but the "electrical" size. The unit of inductance is the Henry, or "H". Most power supply inductors, or chokes, are measured in henries, typically 2-20H. The inductance of a transformer primary may also be several henries. Smaller inductors are measured in millihenries (mH - 10^-3 henries) or microhenries (uH - 10^-6 henries).

Inductor - a circuit element consisting of a coil of wire would on a core material made of ferrous or non-ferrous material. An inductor resists changes in the flow of electric current through it, because it generates a magnetic field that acts to oppose the flow of current through it, which means that the current cannot change instantaneously in the inductor. This property makes inductors very useful for filtering out residual ripple in a power supply, or for use in signal shaping filters. They are frequency-dependent devices, which means that their inductive reactance, or "effective resistance" to AC decreases as the frequency gets lower, and increases as the frequency gets higher. This property makes them useful in tone controls and other filters.

[thousandshirts]

Tabarnac - French Canadian slang. In its literal sense, it means "tabernacle", but in this sense, the word is only used as a vulgar interjection. In French Canadian slang, pretty much the equivalent of the f-bomb, but with no sexual meaning. Also used as a way of saying "Damn it," or, "shit!" Thanks to its ample use of the 'a' vowel, it is an extremely satisfying swear word that lets the energy flow through your throat.

[basile865]

haha

I like how sag is also sometimes called "meow"

[NY Chief]

Damn, Stephane shouldn't you be practicing? Nah, wait a minute. I have your CD give me time to catch up!

Will, can you spell Tabarnac phoenetically so I can pronounce correctly next time I try to play like Stephane?

[5150loveeddie]

Damn, Stephane shouldn't you be practicing? Nah, wait a minute. I have your CD give me time to catch up!

Will, can you spell Tabarnac phoenetically so I can pronounce correctly next time I try to play like Stephane?

Sure Chef!

So Tabarnac would be: let me try this, hummm... ok...... "TA BER NAC" that should cover it!!!

[Ivabiggun]

I hope this is not too late to add but MILLER CAPACITANCE: George's capacity for Miller's. rotflmao

Ivabiggun