Updated 60-100W Hi-Fi Power Amplifier

Posted on Feb 7, 2014

The basis for this amplifier is published as Project 03, and makes no claim to be state of the art  in fact the base design is now over 20 years old. It is a simple amp to build, uses commonly available parts and is stable and reliable. The design featured is a full update on the original project, and although it has many similarities, is re

Updated 60-100W Hi-Fi Power Amplifier
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ally a new design. This new amp (like the original) is based on an amp I originally designed many years ago, of which hundreds were built. Most were operated as small PA or instrument amps, but many also found their way into home hi-fi systems. The amp is capable of driving 4 Ohms, but it is starting to push the limits of the transistors, however, even when used at 4 Ohms, very few failures were encountered. This amplifier, although very simple, is capable of superb performance. This is not an amp to be under estimated, as the sonics are very good indeed, and this is due (in part, at least) to the inherent simplicity of the design. The amp is exceptionally quiet, and is reasonably tolerant of difficult loads. It is an ideal amplifier for biamped systems, and may be operated in bridge mode (BTL) if the selected output transistors have the necessary power ratings (e. g. MJ21193/4) I have heard nothing but praise from those who have built this amplifier the only feedback I have received has been very positive indeed. The sound quality is up there with the very best. Highly recommended ! Note that like the original, there is (still) no output short circuit protection, so if speaker leads are shorted while the amp is working with a signal, there is a very real risk of the transistors being destroyed. The specifications are very similar to those of the original project, but the use of a current sink in the differential pair input...

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