OK, if I want to upgrade to improve sound so what are mods should I need? Beside the speco T7010 are there other candidates can be substituted for output transformer? Also, I need the schematic could someone post it up for me please!
OK, I didn't see my post re-appear so I guess it's lost; I'll try again.
The first recommended upgrade is to a C4S current source plate load on the driver. This was first offered as an upgrade, but shortly after it became a standard part of the kit. It improves the sound quite a bit, and also reduces the hum somewhat. The currently-listed SEX kit C4S upgrade is very similar, and I'd be happy to look over the manual and advise of any changes.
There was, back in the day, an iron upgrade kit that included a Magnequest BCP-15/50mA plate choke and a custom output transformer made for us by another vendor. The original 10-henry plate choke was recycled to replace the 270 ohm resistor in the power supply. The BCP-15 is still available (though Mike at MQ is not taking orders right now due to some health issues). I expect him to come up with a 4K impedance transformer eventually, to upgrade the Stereomour which is basically the same circuit. So far I am not aware of a fully satisfactory substitute on the market; the MQ TFA-2004Jr probably comes the closest.
The coupling cap (0.1uF/630v) and the parafeed output cap (3.3uF/630v) are the most significant ones to replace with better parts - "audiophile caps of your choice" as we say, since favorites change frequently.
The schematic was in the manual, and manuals have been available, however I don't know if there are any manuals that old still around. Doc B will have to address that question.