This Quad 33 Pre- Amplifier has undergone the following improvements:

o The two internal Amplifier boards have had all the electrolytic capacitors replaced using uprated high quality audio-grade capacitors, all the critical resistors replaced by metal film modern equivalents, reducing the sensitivity from 100mv to 250mv and improving the signal to noise ratio  to 6dB. With this upgrade in place you may connect a CD player to the radio 1 & 2 inputs.

o The Phono board has all the electrolytic capacitors and resistors replaced adapting it to 16v.

o The tape input board has been modified to improve bass response.
o The disc input board has been modified to increase the sensitivity compensating for the overall
  reduction in amplification.
o The old and dried out electrolytic balance capacitors on the motherboard have been replaced by
  modern audio grade versions with better tolerance

o Electrolytic capacitors, resitors, diodes and Zeners on the PSU board have been replaced by
  modern audio grade versions. More stability has been achieved by increasing the voltage to 16v.
o Where components have expired due to old age or abnormal usage they have been replaced by
  modern uprated versions, the LES bulb is replaced as a matter of course.

o All soldered connections checked and re-made where necessary.

o Exterior case cleaned and degreased
o The internal chassis and components have been cleaned.
o All printed circuit boards have been dusted and cleaned with a foam cleaner to remove grime.
o New components on the PCB potted to hold them fast to the board ensuring no movement.
o Potentiometers (controls) have been internally sprayed with switch cleaner to remove crackle
  during operation.
o Any potentiometers that are failing will be replaced, the volume pots are prone to failure on Quad 33s and a no-functioning or 'graunching' pot will be replaced with a Modern Alps equivalent without a switch or a new (NOS) Allen Bradley dual 50k log pot with a switch.

(We use the following audio grade electrolytic capacitors:

Nichicon Muse, Panasonic FJ, Elna Starget, RO2 and Silmic)

The unit has been connected to a Quad 303 amplifier, Quad 67 CD player via the radio 2 input, and a Teac cassette deck and has been soak-tested for eight hours continuously.