The Quad 303 is actually a well design unit which can sound superb after recapping with better quality components. The resultant sounds like a valve amp, as per many testaments on the web including http://tech.groups.yahoo.com/group/quadhifi/message/11056
The external chassis was rusting. Hence I used AutoSol to clear the rust up before re-spraying. I chose the following colours as it does justice to the unit.
|After large caps were replaced|
|After recapping with better quality components|
In addition I replaced a carbon resistor on each of the audio boards to "open up" the units, as there was still a slight roughness "round the edges" after recapping and re-biasing. I decide to perform the replacement after some research on the internet.
For the DIY-ers out there, the above were perform according to suggestions by Dada and NetAudio. I choose to use Wima's and Panasonic FC(s). If you decide to revert back to the original Quad sound, it is quite easy. Just replace the big Wima visible on each of the above audio board (next to the 2 caps before the trimmer at bottom of the pix) with a different cap e.g Vishay BC (green) or Evox (grey). And put back the carbon resistor for the "roughness" in the sound quality.