The Charm of Guitar Amplifiers

An electric-guitar store, at some unspecified location, somewhere in the world. Photo: Visitor 7

An electric guitar is an analog sound generator. The difference between an acoustic and an electric guitar is that the first uses a hollow, usually wooden box to amplify the sound, while an electric guitar needs to connect to another box filled with electronic components, generally referred to as an amp.

Any guitar amp here, will be judged solely on its ability to serve three areas where a guitarist needs an amp: 1) to practice, 2) to perform and 3) to record.

In this weblog post, two tribes of people will be encountered: musicians, more specifically members of the Guitarist clan and DIY hobbyists. Guitarists will be quickly dispatched. They know the type, size and brand of amp they want, typically a combo-amp that contains an amplifier and one or more speakers in a single cabinet. Many guitarists consider 40 Watts an appropriate size, although larger and smaller sizes are available. Jazz guitarists may opt for a Roland Jazz Chorus JC-40, rock guitarists for a Fender Hot Rod Deluxe 40. Satisfying their needs is very simple, involving three steps. They must:

  1. Order an appropriate amp online.
  2. Wait patiently by door with guitar, until delivery person arrives.
  3. Unbox amp, plug in guitar (and electricity) and play.

The DIY tribe is not a big, friendly group. In fact, it may have as many people with psychological labels, as musicians. It is divided into at least three clans: cloners, tweakers and circuit benders. Yet, these clans have much in common. DIY tribespeople are difficult to satisfy. They are interested not in playing, but just in the process of building an amplifier. Once it is built, that is the end of their project. A cable may never actually be plugged into the amp. Beyond testing, the amp will probably never be turned on. It will join all those other barely finished, half-finished and barely started projects collecting dust/ rusting/ otherwise decaying in assorted areas of the house/ garage/ or great outdoors. In an effort to avoid collecting more junk, the DIYist may, in desperation, seek out a guitarist, upon whom he (yes, this type of person is almost always male) will bestow his creation.

Cloner clan

Cloners are DIY types who copy a preexisting design from a commercial manufacturer, often involving reverse engineering or the use of circuit schematic diagrams and/or printed circuit board (PCB) layouts. The legality of such a process never enters the mind of a cloner. The results of their labours are seldom for sale, and do not attract the attention of manufacturers. Clones are never perfect copies, since there may be obstacles involved in accessing specialty parts or undertaking mechanically construction. However, the circuit or other distinguishing features should be close to the original.

People recreate an existing design (i.e. clone) for many reasons. The design might be historically important but out of production. so the only way to obtain the component is to build it. Other considerations may relate to costs, sentimentality or skill development. A copy may be built to test design concepts or principles.

In 2019, a cloner will probably build a chip amp, possibly a Gainclone, the most commonly built and well-known amplifier project among hobbyists. It is simple to build and involves only a few readily accessible, inexpensive parts.

The Gainclone is based on a 1999, 47 Labs Gaincard amplifier, an unconventional design with fewer parts, less capacitance and simpler construction than most amplifiers preceding it. It used a 56-watt chip, the National Semiconductor LM3875. This construction breached accepted wisdom, which favored large power supplies and discrete components. The DIY community started building replicas or clones of the Gaincard, which soon became known as Gainclones. Today, chip amp or chipamp is used rather than Gainclone, to describe IC amplifiers made by amateurs.

Tweaker clan

Tweaker clan members spend their time replacing mass market components. The tweaker I remember best did not make amplifies as such, but electronic organs. His starting point was a cheap consumer brand organ (Hammond?). He replaced each and every resister on it with one that was within a fraction of a percent of the ideal value that he had calculated. He had a large business in the Vancouver area, revitalizing church organs. The replacement of cheap/ inferior mass market audio components with high quality substitutes is the modus operandi of the Tweaker clan. Other audio components commonly replaced include capacitors (recap) and operational amplifiers. Op-amps provide power. Since most op-amps have the same pinouts, they can easily be replaced with higher specification components.

Circuit bending clan

The Circuit bending clan is interested in the creative customization of circuits. In the 1950s and 1960s it existed as the Kit building clan, with the Heathkit sept being a large and powerful force, until it suddenly disappeared without a trace. More modern clan members use conventional electronics to experiment. They dismantle machines, adding and sometimes subtracting components such as switches and potentiometers. Members of this clan value noise as much as music, unfortunately.

More recently, additional septs have emerged in the circuit bending clan, focused on microcontrollers. The Arduino and Raspberry Pi septs are currently the two largest, but the ESP32 and Micro:bit septs are increasing their presence.


While the human ear is a marvelous piece of biological engineering, it is far from ideal. The frequency range of hearing is limited, as is its ability to perceive sound pressure. Low dB sounds go unheard, while high dB sounds can permanently damage delicate biological machinery. Hearing ability decreases with age and with exposure to loud sounds, such as rock and roll played at 100 dB, evening after evening. As living creatures, natural selection has favoured some characteristics over others, so that surviving humans are often those who are able to make the most judicious compromises.

Overselling audio

The High Fidelity Society (HFS) will be used as a pseudonym for a business enterprise that sells audio receiving equipment with characteristics that far exceed human hearing capabilities. Yes, I have at one time been the target of a HFS seller who attempted to insult me into purchasing audio equipment I didn’t want or need. Such purveyors use an assortment of unconscionable tactics as a sales strategy. If a dynamic range of 20 to 20 000 Hz is good, then 10 to 30 000 Hz must be better, and 5 to 40 000 best of all. They pretend they can hear the difference. They can’t. Biology puts limits on what people can sense. The commonly stated range of human hearing is 20 Hz to 20 kHz, but sometimes the lower range limit stated is above 30 Hz, and the upper range limit may be 19 or even 17.5 kHz.

Working back from the ear, there is a chain of components that shape sound from an electric guitar: vibrating air set in motion by one or more loudspeakers, optionally, a cable to a power amplifier that produces a high current signal to drive each loudspeaker, that at a most basic level are operated with control knobs including vertical faders to control multiple frequency bands, a real or virtual pre-amp with real or virtual controls that modify tone-shaping electrical circuits or software equivalents, a cable between the guitar and the amplifier potentially eliminated by some form of wireless technology, on the guitar itself – up to multiple pickups, possibly a vibrato bar/ unit, usually volume and tone knobs, any number of strings, a pick held by a human, hopefully with fingers.

Sometimes life may not be so simple. Between the preamp and power amp stages there may be an effects loop or some dedicated amplifier tone circuits. Pre-amps may be stacked into multiple stages (gain stages) which may provide feedback loops from a post-preamp signal to an earlier pre-preamp signal.

Guitars may have passive tone controls, active equalizer circuits in built-in preamps, pickup selector switches and more. There may be other devices between the guitar and the preamp, such as a pedal or other effects.

As one progresses back over from component to component, it is important to know what can be sensed or measured and what can be ignored. At some point one will have to learn something about the propagation of sound. It will be especially important to learn how to make electronic effects: equalization, compression, distortion, chorus, reverberation and more.

Tube vs Solid-state

When a guitarist is dependent on a single tube-based combo-amp, extra tubes had better be taken to every gig. While nobody will notice if a stack or two out of a hundred or more fail to operate become some roadie didn’t pamper it sufficiently and caused a delicate tube to fail, they will notice if a vacuum tube combo-amp fails!

Risking the wrath of one of my closest relatives, I will suggest that using a tube based amplifier, is equivalent to using a cathode ray tube (CRT) based television. There was a time in the previous century when such a choice was justified, but that ended many years ago.

Technological advancements have made low-wattage solid-state amplifiers viable. These are less expensive to build and maintain, reduce the weight and heat, are more reliable and shock-resistant. High-end solid-state amplifiers are uncommon, because many professional guitarists still favor vacuum tubes. Some jazz guitarists are part of a minority that favor the cleaner sound of solid-state amplifiers. The Roland Jazz Chorus, is possibly the best known high-end solid-state amplifier.

Modeling Amplifiers

Modelling amplifiers use microprocessors and software to create digital effects. These can be programmed using a USB or equivalent connection with a desktop computer or laptop, and potentially a tablet or cell-phone.

A modeling amp with plugs for a guitar, a generic pedal, a microphone or two can imitate specific amplifiers (real or imaginary), that can provide an infinitely large number of sounds and tones, of which some might actually be desirable. This ability to simulate specific characteristics comes in a package weighing less than 1 kg (2 pounds).

The secret is to construct a full range, flat response (FRFR) amplification system as the output unit of the modeling amplifier. Guitar input is processed using software based sound processors in the signal chain before the amplifier. This allow guitarists to use PA systems and powered speakers without worrying about their sound being coloured by the amplification process.

The approach is to digitize the input signal and use digital signal processing (DSP) with a dedicated microprocessor. This is an inexpensive and compact device. A dedicated standalone modeler can be connected directly to a recording device or PA system without having to use a power amplifier, speaker cabinet or microphone

Modeling amps include the Peavey Vypyr, Deplike, Roland Cube, Fender Mustang, and Line 6 Spider series. Many DIYers will attempt to clone these using schematic diagrams and other materials intended for service and repair.

Fender Limited-Edition Hot Rod Deluxe IV 40W 1×12 Tube Combo Amp Lacquered Tweed An amplifier suitable for a musician. Photo: Fender

Hot Dog 40 Digital Guitar Combo Amp Specification

Model name: Hot Dog 40
Amplifier Type: Digital
Speaker: One - 12 inch (300 mm) speaker
Inputs: One - 1/4 inch input, 3.5 mm AUX input
Outputs: USB Recording Output, 3.5 mm Headphone Output
Channels: One
Controls:  To be determined
Effects:  To be determined
Wattage:  40 Watts
Cabinet Material: 5/8 inch (16 mm) plywood
Covering: To be determined
Grille Cloth: To be determined
Handle: Integrated Top-Mount Handle
Controls: Plastic knobs, computer control
Other Features: Digital Chromatic Tuner, Bluetooth Audio Streaming, WIFI
Footswitch: Generic 
Dimensions (HxWxD): 16 x 16 x 8 inches (400 x 400 x 200 mm)
Design Weight: < 22 lbs (10 kg)

DIY Sources