When I connected the Snubber (a 47nF paralleled with a 330Ohm resistor), I realized the PCB already has a pair of soldering pads connected to the transformers secondary and the Heat Fuses input.
So, now I´ve done some listening with my HD800, and this LBC amp works tremendously well - those headphone are now full bodied and not so sibilant as they were earlier, altough the SS3602 much treble! Regarding the Snubber mod, it seem´s to do very vell, as the amp are has a really black background and plenty of tight and deep bass, so I can really recommend this mod for this amp, as well as it can be used with every amp, DAC and CD-player etc with AC Voltage input. Do´nt forget to remove the four original 0,1uF cap´s for the rectifiers.
Except the Snubber mod, I´ve also done following below to reduce noise and EMF/EMI:
- Replaced the cheaper 1N400x with BYV27 (as they´re faster and with less noise, giving a cleaner Power to the Voltage Regulators).
- Connected a filter (from a PC´s Power Supply) at the Primary side at the transformer.
- Mounted some aluminium brackets inside the amp (connected to the enclosure) for less noise from neighbour components.
- Applied some glue or double sided rubber adhesive tape between PCB and caps to reduce vibrating movement for them.
- Mounted some caps underneath the PCB at the secondary side (mostly due to their big size, but this may also reduce some inteference from other components).
- Connected the Voltage regs heating plates to chassi enclosure (Silica sheet or similar must be used between the tabs and heating plates, when doing this!).
- Shielded the internal OFC signal cables and the cable between the transformer and amp, connected to chassi Earth.
- Soldered the OpAmp directly to the PCB, without any socket (to avoid bad connection or oscillation from the PIN´s).
- Move the Toroid transformer out from the enclosure, in it´s own metal enclosure at a distance of about 8 inch.
- Connect the amp´s enclosure Earth to main wall outlet sockets Earth (if you have 3 PIN earthed wall outlets). This will help getting rid of any EMF/EMI noise and avoid letting it go towards the signal Earth that´s already separated with 1000pF cap and 100 Ohm resistor.
I will also add some rubber feet underneath the enclosure to minimize vibrations and a Ferrit bead to the high voltage cable, near the amp. And twisting the cables will also reduce EMF/EMI (at any direction; CW or CCW).