The SEP 3 is a 6DJ8/6922 based 5 input line stage. There is an optional 6DJ8/6922 based internal phono board. The gain is 30dB. Noise -85dB. Input impedance 10K. The functions are remotely and touch button activated, the control done through an EPROM. The external power supply uses a 5U4 tube rectifier. It is a very nice sounding unit and some simple parts swaps can improve the sound.
The SEP-1 is good line stage. All GTA products were high value for their price point. To keep the price down, some components were under spec'd. Again some simple resister & cap swaps yield big benefits.
The SE40 is perhaps the best bargain, now and at introduction. It is a parallel single ended 6L6GC design capable of amazing sonics. The SE40 can be configured as stereo or monoblocks. The available mods both address the stressed parts. The Sonicraft replaces coupling capacitors with their own branded metalized polyprop caps. The Loc Vu mod is cheap and DIY. It is far more extensive, solving the reliability issues, replaces PS cap, uses PIO caps for coupling and PS and negative bias circuit. Loc's modkit (MY BIAS! I am a PIO cap guy and I install the kit for folks!), elevates the sound to compete far above the price point.
Go join the GTA Yahoo group. There is a wealth of knowledge and expertise in it archives and membership.
Cheers,
Geary