Yes, the returns you have to live with if you want speed. I tried to double the input speed of the entire system, but did only get down to around 3 seconds, so I settled for my current setup.
The system is much easier than you might think, however it took me a while to reach this point:
(this is the full setup, feel free to scale it down accordingly)
- Put a normal aura node next to each side of the synthesizer and one on top. This is where your power comes in.
- Put red aura in each of those nodes. The one in the middle gets 40000 and the others get 20000.
- Put a capacitor five blocks above the middle node and leave it at a threshold of 1000
- Put a solid block 10 blocks above the synthesizer (so another 4 blocks above the previously placed capacitor)
- Put a capacitor on threshold 1000 to each side of that block, so they connect with exactly one node to the sides of the synthesizer
That is all there is to it concerning aura nodes. You now just have to precisely set off TNT blasts at the rate you want and the system is running. In my setup I have it set so every second all five nodes get powered at the same time, so it uses 5 TNT per second, so pretty hefty price there.
What makes this all work is, that normally the aura capacitors have a short cooldown period where they can't accept any aura. However this seems to not be the case for aura coming from below. For normal aura pumps this isn't a problem because they won't accept aura from above. Also the capcacitor always bursts no matter if it is in cooldown or not, as long as there is enough aura in it. So in this two node system the aura is traveling up and down every second without any cooldown or something like that, producing as much power as you theoretically want.
In total I would consider this an unintended behavior, but for the moment it works if you can give it the amount of TNT required. Later today I can post a few screenshots to show the exact setup of the TNT explosions, this probably took the longest for me to get right because there seems to be a little bit of directional bias happening. The most reliable spot seems to be three blocks away and one block down from every node. For the middle one it's a little bit more complicated, so better to show it later, but you can figure that out by yourself (maximum distance of the blast can be 3 blocks).