== Unanswered Questions ==
- What are the different types of amps?
- Solid State (FET based) - high contrast sound? Solid state refers to devices using silicon and modern semiconductor technology. These devices, as opposed to tubes, produce more high order or high frequency distortions, which can make the impression of a sharper or more crisp sound. Solid state overdrives abruptly and sharply, which is usually obvious when it happens.
- Tube - smooth sound, less contrast in detail? Tubes produce mainly low order, low frequency distortions, which, if one is accustomed to solid state, can seem to make the sound less sharp. Sometimes however, a low-pass filter is used which cuts out the treble, and can produce the same effect. As opposed to solid state, tubes don't react sharply when overdriven, and usually sound better when they are.
- Chip (Transistor?) - Chip amp describes an amplifier that minimizes use of discrete components (for example single transistors, diodes), opting instead for microchips designed for the application. These make good starting projects for beginners because of their simplicity and because most functions are included in the chip with no maintenance or adjustments necessary. However the fabrication of components into chips has certain tradeoffs, because they all go on the same die. Power is limited without using external discrete power components, because it is difficult for such a small die to dissipate enough power quick enough, and thermal interference between components can be high. Parasitic effects are also increased, which can lead to lower performance. Furthermore, microchips are designed to meet certain specs, and since audio quality has no known reliable indicator, a well-spec'd chip is not guaranteed to make sonic impressions.
- Pass Labs - Pass Labs is a reference to Nelson Pass, legendary for the consistent quality of his audio designs and products. Pass maintains an active connection with the DIY community, having released many projects for DIY builders.
- Class A - output amplifiers are always 'on'; power hungry - Class A is generally thought to be the most transparent form of amplification, because all devices remain on during the signal, avoiding high-frequency distortions caused by devices switching and and off. Still, this is an area of differing viewpoints
- Class B - two amplification stages, one for peaks another for troughs? - One device provides positive current, then switches off as the other provides the negative current, and vice versa. This conserves a lot of energy. The sudden switch tends to cause indomitable high frequency distortions, which is why honest class B is rarely used for audio applications.
- Class AB - operates in Class A mode for the lower power then switches to class B as the amplifications level is increased. - This is the most common power amplifier type. The class A region between switching greatly reduces switching distortions, while still conserving a good amount of power.
- Class D - Amplification stage switches on when amplification is required and off when it's not (aka switching Amp). - This type of amplifier switches rapidly between full positive and full negative, varying the time spent in each in order to vary the average voltage of the output. This is averaged into a useable audio signal by a filtering stage. This amplifier is intended to be very efficient and also powerful, useful for applications like car audio. Because of the high frequency noise and high distortion typically achieved, class D is only recently gaining interest from customers as technology advances.
- PA Amplifier - PA stands for Public Address. These amplifiers are generally, unless bought from a specialized dealer, not made for sound quality. The important specs are high power, for producing necessary volumes across large spaces, and legibility. Voice PA systems sometimes employ an equalizer boost for voice frequencies, to cut out other sounds which are not necessary, may hinder legibility and will waste power.
- Mixer Amplifier - an amp with a built in mixer - A mixer is used to combine the signals from all the microphones and inputs in a recording session to a fixed amount of tracks for the master recording. Often equalizers or tone controls are included, but the function of a mixer is not expressly focused on frequency filters.
- Mixer -a device that allows a user to modify different frequency ranges within the sound signal through the use of sliders
- What are the typical sound characteristics of the different types of amps - I recommend to read "http://www.milbert.com/articles/sound_of_distortion". Jan Didden is actually a member on this forum, and you may be able to ask him for a full copy of the article with the missing figures. Understanding this will help you categorize the distortions of different types of amps and how they relate to the perceived sound. For the record, not all SS amps sound like SS, some SS amps sound like tube amps and so on. Nothing is set in stone and often great amplifiers will make this obvious.
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