This DC servo amplifier will work with 3 phase AC or with DC as a power source.  It has high current transistors in parallel so it can drive alot of current.  It turns a DC signal from your servo circuit such as the LM628 into a power signal that can drive a VERY large servo. 

Visual Basic source code for this project here: http://www.emarket-usa.com/anuncio-80401341-DC-Servo-Motor-LM628-Motion-Control-Visual-Basic-Source-Code-Arizona-Phoenix.html

You can see an example of what this is capable of driving by viewing the movie above.  The whine in the background you hear is this servo amp. 

I have already figured out how to connect this so they work.   My setup used a DC power supply connected into the amp.  Then a DC servo signal was fed into the input.  The motor was connected to the amplifier output.  They are already wired up.

I have several of these. Asking 50$ per.