Modding headphone amp in a Philips CD721
Jul 10, 2006 at 10:08 PM Thread Starter Post #1 of 1


100+ Head-Fier
Nov 5, 2003
i have a philips CD721 player in my office with built in headphone amp. The amp is a NRJ4556, runs on +/- 12V, gain is 2.5
Would any of the following be likely improve the sound (which isn't bad but....)

Adding some caps to the +/- rails, i was thinking several k uF bypassed with polyprop or polystyrene
Swapping chips, if so to what? 2134?
The output goes through 120 Ohm then paralled to 1K Ohm. Can i jumper the 120 Ohm resistor?
There are no blocking caps on the headamp board, i am getting a pop at the end and beginning of each track, would adding caps help? Suggestions?

i do not have the scematics for this, and have not reverse engineered the main PCB yet.

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