Have you considered to simply buy an unexpensive 303 clone? I think I have seen MAM MB-33 for 99,- Euro: http://www.netzmarkt.de/thomann/artikel-152119.html?ARTTEXTSPRACHE=D&WAEHRUNG=DM&PRL=&sn=9e9cc62524e9bfa8241dcaad3feb3b0f (Ignore the nonsense about "24dB filter" at the link. I have no idea why they write this.) JH.