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 is a medium power guitar amplifier is recommended especially for portable amplifier. The amplifier is a combination between a simple integrated audio driver, LM391-80 and a stage of output power designed contratemps with bipolar transistors. Thermistor NTC, which is in temperature contact with output power transistors, allows to separate AO LM391 power stage when it heats too much. The start of the thermal protection is at a NTC flow current NTC of approximately 200uA. Electrolytic condenser asure a “smooth start” to remove clicks that may occur when connecting the amplifier. It can happen that the protection can be too sensitive, in that case certain adjustments are admitted in the value of R4 or thermistor. The standby current can be adjusted with P1. This potentiometer is initially 0 and then is adjusted to achieve a current of 50mA. Current can be increased up to 400mA if you want low distortions. The power transistors are placed on the same side of printed circui...