Cathedral Gainclone Project
Background
In 1999, 47 Labs introduced the Gaincard amplifier. The Gaincard shook the
audiophile community[citation needed] with its unconventional design. It had
fewer parts, less capacitance and simpler construction than virtually anything
preceding it, and relied for amplification on a 56-watt chip, the National
Semiconductor LM3875. These construction techniques went against the accepted
wisdom of the time,[citation needed] which favored large power supplies and
discrete component construction. This Gaincard was estimated to cost less than
100 USD in parts, but it sold for 3300 USD with its small power supply.
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" on the popular Audio
Asylum board (ca. 1999;[2][3]). Triodont (née Ray Salamat) 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 (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.
Typical characteristics
The fully insulated TF model LM3886
A power opamp or audio opamp chip such as the National Semiconductor LM1875,
LM3875, LM3886, or LM4780, which is a dual LM3886.
A physically very 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 1000 µF).
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.
Sound
Most designs are very effective and produce 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, over temperature protection and short circuit
protection.
(from WIKIPEDIA)
Return to Amps
Cathedral gainclone features all aluminum case, 400 volt amp toroidal transformer, 77,600 microfarads of capacitance power, silver input wiring, gold plated connectors, gold plated board traces, Nichicon FW audio grade capacitors, capacitor bypasses, etc.