TECHNICAL DESIGN
Making bespoke guitar amplifiers and with the advent of acoustic guitars it is no surprise to
get a request for a quality custom acoustic amp. Not having made one before i was
surprised that the main request was to simply amplify the tone from the expensive guitars
that the customer owned. What was more surprising there seem to be next to nothing on
the market that was not full of digital effects and numerous controls that coloured the
natural tone.
Virtually all modern amplifiers are built using printed circuit boards, which contain conductor
tracks that connect components together, these conductor tracks often run very close to
one another. When this happens a small capacitance is produced between them, the result
of which is a substantial loss in both high frequency response and harmonic richness.
The Cornell Acoustic amplifier is designed to avoid this by having specific point to point
wiring.
Components in the amplifier are mounted on a specially designed board using eyelets and
Turret Tag’s that are hand riveted onto the board where the components are mounted.
These components are then sealed using a conformal coating to prevent noise and
reduction of component life caused by moisture penetration.
The steel chassis holds specially designed, interleaved, transformers, wound with
impregnated paper. The design ensures a very close reproduction of the full harmonic
spectrum of your guitar’s pick-ups.
The cabinet is made of a rigid construction using high quality Pine and Ply wood. The
covering is both heavy duty and burn resistant, The cabinet is handsomely finished and
features original fittings.
The pre-amp is designed to be simple in use, and yet produce the wide range of sounds
that the musician of today expects from a professional amplifier.
The ‘Tone controls are designed to work over the entire frequency range of your guitar,
allowing for increased amounts of low and high frequency adjustment.
The Output stage.
The output design is a Class ‘AB’ and is achieved by means of a negative voltage applied
to the grid of the output valves,
Cathode bias resistors are also employed to stabilise current flow throughout the life-time of
the valve. The voltage across each resistor will vary with the valves characteristics. When
these voltages are equal, then each valve is drawing the same amount of current and the
valve set is ‘matched’ resulting in maximum output and long life.
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