Gainclone
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Gainclone or chipamp is a type of audio
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power su ...
made by do-it-yourselfers, or individuals interested in
DIY audio DIY Audio, do it yourself audio. Rather than buying a piece of possibly expensive audio equipment, such as a high-end audio amplifier or speaker, the person practicing DIY Audio will make it themselves. Alternatively, a DIYer may take an existing ...
. It is a design based on high-power
integrated circuits An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
, particularly the
National Semiconductor National Semiconductor Corporation was an United States of America, American Semiconductor manufacturing, semiconductor manufacturer, which specialized in analogue electronics, analog devices and subsystems, formerly headquartered in Santa Clara, ...
Overture series. The Gainclone is probably the most commonly built and well-known amplifier project amongst hobbyists. It is simple to build and involves only a few readily accessible, inexpensive parts. As an amplifier, it is highly regarded by many in the DIY community.


Background

In 1999, 47 Labs introduced the Gaincard
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power su ...
. The Gaincard shook the
audiophile An audiophile (from + ) is a person who is enthusiastic about high-fidelity sound reproduction. The audiophile seeks to achieve high sound quality in the audio reproduction of recorded music, typically in a quiet listening space in a room with ...
community with its unconventional design. It had fewer parts, less
capacitance Capacitance is the ability of an object to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are two closely related ...
, and simpler construction than virtually anything preceding it, and relied for amplification on a chip, the National Semiconductor LM3875. These construction techniques went against the accepted wisdom of the time, which favored large power supplies and discrete component construction. This Gaincard was estimated to cost less than in parts, but it sold for with its small
power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, electric current, current, and frequency to power ...
. Controversy ensued after a number of positive reviews.


Modern usage

The DIY community started building replicas or "clones" of the Gaincard using integrated circuits from National Semiconductor and other manufacturers in an attempt to see if good sound could be obtained, thereby the term: "gainclone". The name was first coined by a poster called "triodont" (Ramon Salamat) on the popular Audio Asylum board (ca. 1999;audioasylum.com - 47 labs gaincard-based DIY amp hits it out of the ballpark!
/ref>audioasylum.com - Re: anyone know how to convert a gaincard into a headphone amp?
/ref>). "Triodont" tried to replicate the 47 Labs Gaincard amplifier for his own personal use and reported about it on the internet forum. Various modifications or improvements have been made to the original application circuit found in National's design notes since. The simple circuits were easy to make, and some started offering
printed circuit board A printed circuit board (PCB), also called printed wiring board (PWB), is a Lamination, laminated sandwich structure of electrical conduction, conductive and Insulator (electricity), insulating layers, each with a pattern of traces, planes ...
s and kits to make construction even easier. The design concept has expanded and become rapidly more popular over the last few years as the simplicity of the design and availability of parts make it within reach of even a novice constructor. Now, the term "Gainclone" could apply to almost any amplifier based on a power
integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
of some type, from any manufacturer. In fact, the more common term today for such amplifiers is "chipamp" rather than "Gainclone", as the desire to copy the Gaincard has given way to broader attempts at using IC amplifiers.


Typical characteristics

* A power
opamp An operational amplifier (often op amp or opamp) is a DC-coupled electronic voltage amplifier with a differential input, a (usually) single-ended output, and an extremely high gain. Its name comes from its original use of performing mathemat ...
or audio opamp chip such as the
National Semiconductor National Semiconductor Corporation was an United States of America, American Semiconductor manufacturing, semiconductor manufacturer, which specialized in analogue electronics, analog devices and subsystems, formerly headquartered in Santa Clara, ...
LM1875, LM3875, LM3886, or LM4780, which is a dual LM3886. * A physically very short
feedback loop Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause and effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handle ...
. * Miniaturised construction with short path lengths throughout the circuit. * Minimal extra components, usually of high quality. * Can be made using point-to-point construction rather than a
PCB PCB may refer to: Science and technology * Polychlorinated biphenyl, an organic chlorine compound, now recognized as an environmental toxin and classified as a persistent organic pollutant * Printed circuit board, a board used in electronics * P ...
. * The power supply is often built in a separate chassis from the amplifier. The National Semiconductor chips come in two versions. The "T" model is not insulated and has better heat transfer properties, but it needs insulation when mounted on a heatsink if the heatsink is connected to ground. The "TF" model, as in the picture, is covered in plastic, and thus insulated, but it has less efficient heat transfer properties, which means it can't run continuously at full power. The "T" model is recommended for heavy-duty applications.


Sound

Most designs produce high-quality sound, even though some audiophiles consider chip-based amplifiers to be inferior to their discrete counterparts. The chips have been designed to incorporate a number of desirable features, including excellent
power supply rejection ratio In electronic systems, power supply rejection ratio (PSRR), also supply-voltage rejection ratio (''k''SVR; SVR), is a term widely used to describe the capability of an electronic circuit to suppress any power supply variations to its output signal. ...
, fast response, accurate
bias current In electronics, biasing is the setting of DC (direct current) operating conditions (current and voltage) of an electronic component that processes time-varying signals. Many electronic devices, such as diodes, transistors and vacuum tubes, wh ...
, over-temperature protection, and short circuit protection.


References


External links


LM4780 info
{{Webarchive, url=https://web.archive.org/web/20061005162331/http://home.pacific.net.au/~gnb/audio/lm4780.html , date=2006-10-05



Audio amplifiers Do it yourself