Gainclone
From Wikipedia, the free encyclopedia
Gainclone or chipamp is a term commonly used to describe a type of audio amplifier made by do-it-yourselfers, or individuals interested in DIY audio. It is a design based on high-power integrated circuits, particularly the LM3875 from National Semiconductor. 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.
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[edit] Background
In 1999, 47 Labs introduced the Gaincard amplifier. The Gaincard shook the audiophile community with its unconventional design. It had fewer parts, less capacitance and simpler construction than virtually anything preceding it, and relied on a 50 watt chip for amplification, the National Semiconductor LM3875. These construction techniques went against the accepted wisdom of the time, which favored large power supplies and discrete amplification. This Gaincard was estimated to cost less than $100 in parts, but it sold for $3300 with its small power supply. Controversy ensued after a number of positive reviews.
[edit] 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" on the popular Audio Asylum board (ca. 1999; [1] )). Triodont (whose real name is Ray Salamat) was the first known person who tried to replicate the 47 Labs Gaincard amplifier (for his own personal use) and who reported about its inherent goodness on the internet on a widely-read forum, unknowingly creating the encouragement that audio do-it-yourself hobbyists needed to try out this heretofore revolutionary simple amplifier design/topology. Various modifications or improvements (depending on how you look at it) have been made to the original application circuit found in National's design notes since then. The simple circuits were easy to make and some started offering printed circuit boards 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 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.
Controversy over these Gainclones still exists, and variations have spawned. There are hundreds of web sites with examples, kits, circuits, and descriptions of the Gainclone amplifier.
[edit] Typical Characteristics
- A power opamp or audio opamp chip such as the National Semiconductor LM1875, LM3875, LM3886, or LM4780, which is a dual LM3886.
- A very physically short feedback loop
- Miniaturised construction with short path lengths throughout the circuit
- Minimal extra components, usually of high quality
- Small power supply filter capacitors (often around 1000uF)
- Can be made using point-to-point construction rather than a PCB
- 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. 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.
[edit] The Sound
Most designs are very effective and produce extremely high quality sound, even though some audiophiles consider chip-based amplifiers to be inferior to their discrete counterparts. Many others, however, are astonished by what these amplifiers are capable of. The chips have been carefully designed to incorporate a number of desirable features, including excellent power supply rejection ratio, fast response, accurate bias current, overtemperature protection and short circuit protection.
[edit] Comparisons and Attempts to Duplicate the Gaincard
Although the inspiration for the Gainclone comes from the Gaincard amplifier, not many try to copy the insides because the internal layout of the amp is a bit odd to say the least.
There was a long lasting debate going on in several DIY forums whether or not the two images (below right) show the real Gaincard or a clone. The US importers denied that the images showed the innards of their product, but a more recent image (below left), given to the 6moons editor by the US importers, shows essentially the same components. The Gaincard images were eventually analyzed in detail and converted into a schematic by Mick Feuerbacher, which has led to a consistent picture.
 Inside of the original Gaincard amp |
 Printed circuit boards of the Gaincard |
[edit] The modern Gainclone
The most well-known Gainclone implementation is the one from Brian Bell and Peter Daniel. The design is a collaborative effort from members of www.diyaudio.com, the world's largest DIY audio forum.
From time to time the PCB has been made available through a groupbuy at diyaudio, but PCBs and kits can also be obtained from www.chipamp.com, www.audiosector.com and www.madaboutsound.com. There are other PCBs and kits available, with a few from commercial sources, but most come from hobbyists.
 Gainclone printed circuit board of Brian Bell and Peter Daniel |
 Gainclone designed by Per-Anders Sjöström |
 Another example of a modern Gainclone designed by Rod Elliott |
 This Gainclone is designed by Mauro Penasa. He has designed a very special feedback |
 Gainclone implementation made by Damian Antoniak |
[edit] Links
- Images
- Gainclone webring A webring consisting of websites with Gainclone content, mostly DIY.
- Gallery
- Forums
