The OD-9 board has many parts removed in preparation for our SILVER mod. Much of it's TS9 circuit board is emptied because it no longer uses the TS9s FET switching. So there is less circuitry in your signal path for a clearer, purer tone. I recommend the OD-9 over the TS9 for best tone both ON and OFF. The true bypass switch is a little different feeling from a Boss or Ibanez switch. Like all true bypass pedals it goes down and back up to switch, unlike a momentary switch which just sends a pulse when you touch it.