guru20,
Hello, and thanks for your interest. Many mods are available for the T-Max, and I think that I have inserted most of them in my T-Max. But, others come before me to whom I must pay tribute: Kevin Kissinger and PAiA's 'Excellent' Scott.
Kevin Kissinger is extremely well versed on the available modifications to the T-Max. He has a great mod post devoted to the T-Max somewhere in ThereminWorld. I will look for it and link it here.
http://www.thereminworld.com/forum.asp?cmd=p&T=169&F=10
PAiA has an excellent mod page for the T-Max available in the PAiA website. (As does the excellent PAiA service representative, Scott. Fire off a letter to Scott, he aims to please.)
The crux of the coupling mods has to do with soldering one end of a 10K resistor at a certain point on the parts side of the board, soldering a wire to the free end of the resistor, soldering the end of that wire to the middle lug of a SPDT micro-mini switchthat has been installed into the frony panel of the PAiA printed front panel. Then, solder another wire to one of the outside lugs of the micro-mini switch and solder that wire's free end to the appropriate point on the parts side of the circuit board.
Kevin Kissinger's circuit board points are R6 and R11 on the side of the resistors closest to the tuning lugs,(inductors). PAiA's circuit board points are R4 and R9 on the side of the resistors closest to the tuning lugs,(inductors).
K.Kissinger's coupling circuit board source points and PAiA's coupling circuit board source points are not the same, hence many more tonal options-- albeit, with some range resrictions as a trade-off. I have one switch to utilize Kevin's suggestion and another to use PAiA's. I can use them both at the same time, or choose neither, and let the original milky smooth T-Max timbre speak out.
PAiA, also has a mod to boost the Sqare wave timbre. One may use the SPDT switch idea to switch in and out of the T-Max design timbre to the mod as well. Kevin also has thoughts on this.
Also, I have some thoughts on the implementation and positioning of the Midi-Fader board, but will save that for another session.
The T-Max is a great kit! Good Luck, guru20!
teslatheremin