I wrote Dr. Lloyd about an upgrade. This was his reply:
The Octal 6A SE has, in addition to the Auricaps, Caddock 0.75 W metal film resistors in the SRPP stage, and Riken 1W carbon composition resistors in the CF stage. Also it has Black Gate capacitors in the power supply (the 47-47-47uF filter chain is replaced by 150-22-22uF, all at 350V. The cathode bypass capacitor in the CF stage is also Black Gate. The volume control is a 32=step Noble plastic element unit. I haven't done a comparison listening test against the stock Octal 6A but I have compared the Ultra 4A preamp with Auricaps (no other premium parts) to the SOlen (stock) unit, and the soundstage and imaging (friont-to-back) are definitely enhanced. I also found that Black Gates in the power supply of the Ear+ enhanced the resollution and bass tightness. So I would estimate the SE version of the Octal 6A represents a sonic improvement iover the stock unit, vut I don't know what are the critical components. The Auricaps are certainly a big factor in soundstage and imaging. You can get all the parts for an upgrade from the Parts Connexion. I think I used 18K and 100K RIkens in place of the stock 20K and 110K resistors. I will attach the schematic.
Good luck if you plan to continue your upgrade--if you have any problems, let me know. One other thing--if you have a mechanical buzz from the transformers, I suggest while you are replacing the power supply filters, you remove the screws threaded into the laminations of the Hammond 230 V secondary power transformer and epoxy of double-sided tape it in place instead. This usually eliminates all mechanical noise. You will need a separate screw to hold down the terminal strip. The filament transformer seems to be happy with the screws.
Regards,
Lloyd
