AmplifierCircuits

Guitar amplifiers are always an interesting challenge. The tone controls, gain and overload characteristics are very individual, and the ideal combination varies from one guitarist to the next, and from one guitar to the next. There is no amp that satisfies everyone's requirements, and this offering is not expected to be an exception. The preamp is now at Revision-A, and although the complete schematic of the new version is not shown below, the fundamental characteristics are not changed - it still has the same tone control "stack" and other controls, but now has a second opamp to reduce output impedance and improve gain characteristics. One major difference from any "store bought" amplifier is that if you build it yourself, you can modify things to suit your own needs. The ability to experiment is the key to this circuit, which is although presented in complete form, there is every expectation that builders will make modifications to suit themselves. The amp...

This small amplifier was intended to be used in conjunction with an electric guitar to do some low power monitoring, mainly for practice, either via an incorporated small loudspeaker or headphones. The complete circuit, loudspeaker, batteries, input and output jacks can be encased in a small box having the dimensions of a packet of cigarettes, or it could be fitted also into a real packet of cigarettes like some ready-made units available on the market. This design can be used in three different ways: Mini Portable Guitar Amplifier Max output power:  1.5W @ 9V supply - 8 Ohm load; 60mW @ 3V supply - 8 Ohm load Frequency response:  Flat from 20Hz to 20kHz Total harmonic distortion @ 100mW output:  0.2% Max input voltage @ 3V supply:  8mV RMS Minimum input voltage for Fuzz-box operation:  18mV RMS @ 3V supply Current consumption @ 400mW and 9V supply:  200mA Current consumption @ 250mW and 9V supply:  150mA Current consumpti...

General Description This design adopts a well established circuit topology for the power amplifier, using a single-rail supply of about 60V and capacitor-coupling for the speaker(s). The advantages for a guitar amplifier are the very simple circuitry, even for comparatively high power outputs, and a certain built-in degree of loudspeaker protection, due to capacitor C8, preventing the voltage supply to be conveyed into loudspeakers in case of output transistors' failure. The preamp is powered by the same 60V rails as the power amplifier, allowing to implement a two-transistors gain-block capable of delivering about 20V RMS output. This provides a very high input overload capability. Features: Sensitivity: 35mV input for 40W 8 Ohm output 42mV input for 60W 4 Ohm output Frequency response: 50Hz to 20KHz -0.5dB; -1.5dB @  40Hz; -3.5dB @ 30Hz Total harmonic distortion @ 1KHz and 8 Ohm load: Below 0.1% up to 10W; 0.2% @ 30W Total harmonic distortion @ 10KHz a...