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Addendum

2/21/01: Corrected mislabelled transistor part number: 2SC1815 (was 2SA1815).

9/5/01: Corrected mislabelled transistor part number: 2SC3675 (was 2SC367).

2/12/2002: Richard Albers built the following version of the CDEA amp with some interesting modifications of the original circuit. He writes:

I have changed the 2SK389 FET for a MAT02 Dual Transistor in the first Stage of the CDEH-Amp. There were no problems, and it all worked fine from the start. It sounds much cleaner then with the Dual-Fets now, and I guess they add less harmonics to the music.



In the third Stage of the CDEH-Amp, I have changed the Voltage-Divider 350K/20K, which sets the Bases of the SC3675 at ca. 20V. For the 20K Resistor i have put in a 20V, 1.3W zener. For proper working, I set the current through the zener at 7mA. Two 25K ohm, 5W Mills non-inductive wirewounds replace the 350K, dissipating ca. 2.2W of heat. To reduce the zener noise, I have put a 4.7uF tantalum together with a 47uF electrolytic capacitor in parallel with the zener diode. Noise is no problem.



The Cabinet is a very simple construction, with the advantage of ease changing components or parts. There is only a wooden base with two side-panels. The front is the large heatsink together with an aluminium-angle. A suitable top-cover is under construction. The whole construction could be made way smaller, all parts on one pcb, with a smaller toroid-transformer, and all built in a industrial case, but for my own usage, it's ok.



The two smaller transformers under the wooden cover are the 10H-chokes for the high voltage power supply. The little transformer on the bottom generates the bias-voltage. The oversized big-one is a special-made 250W transformer, from Experience-Electronics in germany. The electrolytics are from EPCOS (Siemens).

This is a further way to tune-up this fantastic machine. Together with the MAT02 dual-bipolar input device and using only the best parts you can get, such as non-inductive Caddocks, very low ESR electrolytic caps in the high voltage section, and so on, there is no better electrostatic headphone amp in the world. It sounds just fanstastic!