Vermes
Advanced Member level 4
It is a processing of Cambridge Audio CD D300. The original construction consists of two boards. First of them, digital board, is responsible for servos and display control. This classic application is often used by many manufacturers in devices produced by them.
The second board – analog one, is equipped with C/A converter, optical outputs and BNC.
The tiny chip from the side of print is DAC – the main component of the whole CD. Although the preamplifier was shielded with copper, there is no shielding on the converter.
It is a Chinese converter CS4338 from Cirrus Logic with drive output. Due to the fact, that the original device uses electrolytes of poor quality, it had to be changed to foil ones. The supply voltage of the power amplifier was too low (+5V/-5V, which at output signal equal about 2,5V is too low voltage). Chip in the preamplifier is NE5532 – not too bad, but it could be a better one.
Changing the electrolytes into foil ones and increasing the supply voltage of the preamplifier improved significantly the quality of sound. Analog part of the device remained on the original state, but tube part was added, so you can compare the result. Of course, analog part can be removed, especially if you do not want any distortions caused by feedback.
Tubes are E88CC from Tesla powered by 160V. Preamplifier is an anode follower operating in A class with dynamic active supply.
The original application of the amplifier had gain equal x10 and for the D/A you need x2 gain.
Link to original thread (useful attachment) - Modernizacja (tuning) Cambridge Audio D300/lampizacja.