Sadly for me there are opposite conventions in polarity between the guitar power supply 2.1mm connector and pretty much everything else in the known universe. The only multi-output power supplies are intended for guitarists, and sometimes "centre positive" devices fly in from outer space; in my (19") case, a Waldorf Blofeld, a GEM RP-X, and a Kenton Thru-5. All of these are powered perfectly well by these leads, and the fact that they are red reminds me of the extreme levels of stupidity that exist in the guitar fx multiverse and prevent me connecting something up with the wrong polarity, which would be so easily done.