Quad 303 Full Upgrade

This full amplifier upgrade is based on the original  Net Audio 303 upgrade. Fidele worked with Net Audio on 303 upgrades by providing a build and test service for Net Audio when required. There is a link to Fidele from the Net Audio web site.

For this upgrade the amplifier and power supply modules are completely re-built with all new components. The power supply and output capacitors are replaced and increased in capacitance. The output configuration is changed to a 'push-pull' design and the output transistors replaced with high quality audio transistors.

This upgrade provides the following:

  • Replace Power Supply capacitors with 2 x 4700uF
  • Replace output capacitors with 2 x 10000uF
  • Add by-pass film capacitors to main output capacitors
  • Replace amp module electrolytic capacitors with Elna Silmic
  • Replace input capacitor with film capacitor
  • Add Constant Current diode sources for TR101 and Bias Circuit
  • Replace trimmer pots
  • Replace the output inductor with high current type
  • Reduce output current limiting (except for use with ESL57s)
  • Replace all amp module transistors with modern audio transistors
  • Replace all amp module resistors
  • Convert the output to 'push-pull' drive
  • Replace output transistors with complementary On Semi MJ series audio transistors.
  • Replace the rectifier bridge module with a modern bridge rectifier
  • Completely rebuild the power supply module including small modification to increase temperature stability.
  • Replace the power supply output transistor with On Semi MJ series power transistor.
  • Replace the speaker connectors with new binding posts
  • Full alignment and bench test

    The cost for this upgrade is £285.00 plus £25.00 for return shipment to the UK. Please enquire for shipping to other locations.