Page 12 - Triwatt Custom Lead Amp Builder's Guide

Guitar Amplifier Basics

Electric guitarists can be fairly criticized for their reluctance to change to new ideas
and technologies; however, there is no doubt that a classic 1950’s guitar and tube
amplifier in good condition still sounds great in modern recordings. This is a
testament to good design from the start. What has improved today is consistency,
and the cost benefits of production line manufacturing. This is offset by the rarity of
good guitar wood (it makes a huge difference, even on an electric guitar), increased
labour costs for both guitars and amplification equipment, and the availability of good
and consistent quality tubes.
There is also an element of nostalgia, with memories of many of the great players of
years gone by, and the desire to use the same types of instruments and equipment to
recapture the magic. Vintage instruments and equipment have also become valuable
collectors items (some with very inflated prices) which adds further to the desirability
of older tools of the trade. There has been a recent trend by many companies to re-
market their original instruments and equipment; new guitars can even be bought now
‘pre-aged’!
This desire for vintage equipment is also related to guitarists’ reluctance to part with
tube amplification, and there are many reasons why tube and solid state amplifiers
behave differently. Quite simply, if players prefer the sound of tubes, they will
continue to buy and use them. Below are some fundamentals.

Input Impedance Typically 1M, 500K minimum (humbucking pickup guitars
have volume pots up to 500K, single coil pickup guitars typically of 250K) .

Tone Controls Magnetic guitar pickups are inductive, and require
compensation, although this opportunity is also used for tone enhancement, not just
correction. Without compensation, they have a strong low middle emphasis and
little high frequency response - overall a very muddy and muffled sound. This is
why typical hi-fi Baxandall treble & bass controls are unsuitable.

To hear the natural sound of a pickup, use a typical guitar amp with the middle set to full,
and bass and treble on 0. This is actually sets a flat response in the amp (see below). Expect
to hear a muffled and muddy sound. And that's the whole point of these tone controls
providing compensation for the natural sound of a pickup - the middle control simply
boosts the pickup's normal ‘middley’ sound. The treble and bass controls do the opposite -
they boost higher and lower frequency levels, leaving a notch in-between for middle cut (see
the Fender/Marshall comparison below). So with typical settings of a bit of bass, middle
and treble, the overall tone equalization complements the natural pickup sound for a
balanced response of lows, mids and highs.

TrinityAmps TRIWATT Builders Guide Ver. 2.31.docx
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