Quad 405 Current Dumping Amplifier
The Quad 405 and the later much revised Quad 405-2 Current Dumping Amplifiers are one of the most unique and much loved classic british made power amplifiers of the last twenty five years. The skill of the design, the engineering and thought that have gone into this amplifier make it stand out as an oustanding product and it is no coincidence that the Quad 405 first won a Design Council Award 1976 and then later in 1978, The Queen's Award for Technological Achievement, the only Hi-Fi manufacturer to have won such awards.
The Quad 405 and 405-2 boasts a generous 80 watts per channel into 8 ohms, and has a very neutral open sound that is quite detailed in some areas but just slightly lacking in others. Part of the reason for this is the age and quality of some of components. Fortunately for those who are willing to invest a little time and money and get companies such as Net Audio to upgrade the op-amps and electrolytic capacitors, these amplifiers can compete with the best modern day hi-fi has to offer. There will be more articles to follow on upgrading the Quad 405 and 405-2 in later posts.
The other beauty of these amps is because they operate in pure class A mode as opposed to class AB which requires bias adjusting after time, the amplifier will never sound different or degrade overtime so long as the capacitors are replaced every 10-12 years. This means that because of their build quality, the Quad 405 and 405-2 should keep on going and going without issue.
Since this article was originally written, Net Audio have started manufacturing brand new "Mk 3" boards for the Quad 405 and 405-2. More information can be found here, but having listened to them for the last six months, these new boards for the Quad 405 and 405-2 offer significant improvement especially if used with Net Audio's Dual Mono Power Supply.
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