After unsuccessful attempt to contact the representative in Germany about upgrading to series II. I decided to upgrade this recent purchase, for my system.
Replacement of electrolytic capacitors. From several models that were tested including the original reference (10000uF / 80V from nippon chemicon, SMH series), I opted for the nichicon KS (M) for its sound performance. From KME 1000uF / 63V and 470uF / 100V series has been replaced by the nichicon (KW) series. These capacitors are from the power supply of the voltage amplifier and power supply to the AD842. Also on the protection circuit board the electrolytic capacitors were replaced.
The Spectral DMA 150, uses Vishay RN55D resistors (1% - 100ppm). I like this series but prefer the RN55E version (0.1% - 25ppm). These resistors (RN55D) were replaced by the RN55E version, those that work in current mode, and those that work in voltage mode, were replaced by RC55Y series of welwyn (0.1% - 15ppm), signal and feedback path.
The resistances of the main board, (circuit protection) and protection board kept everything the same.
Other resistors have been replaced from power supply for output mosfet in this case I chose the Vishay serie RS 5W 1%.
("... Interestingly, the sense of orientation of the resistances has an influence on the sound result. In this case I chose the opposite direction of the screen printing, the current through which it circulates ...")!!!
The rectifying bridges for output mosfet, I opted for another ref. (GBU806 from DIODES INC.) For the voltage amplifier, I prefer ultra fast diodes but not schottky diodes. It was designed four pcb to place four diodes (RHRP860) and adapt to the motherboard. This is because there are no ultra-fast bridges on the market with the same original box type.
The suspension of the transformers has been updated, the original was very hard.
As soon as possible, I put photos...
cheers