1/4" can be a few things....the TRS Tip-Ring-Sleeve or Balanced or Unbalanced which is TS - Tip-Sleeve. Also 1/4" stereo TRS. I know I will be corrected here, but with under 20 ft of a 1/4" run and being mono channels, it is quite possible to run an unbalanced 1/4" between the Pre/Pro and the amp. No need for a TRS. But as pointed out an adapter is given. but if you have the AMp seprated from the Pre?pro more than 20 ft then chances are you will run a TRS or Balanced 1/4".