who makes amps for RCF boxes - is it Powersoft ?

An anecdote regarding the old RCF/Mackie Art 300/500 amplifiers, I used to do the electronics repairs for a couple of music shops, one shop had a service contract at a hotel that had 20 of the Art 300A speakers permanently installed (at height) in a largish ball room, these were powered 24/7 and the system worked well for several years, then one weekend 5 died, then a few days later another 3 failed.

The fault was simple in that the amplifier has two 100ohm 1.6watt resistors that drop the +/- 40v rails down to feed the +/-15v rail regulators, one of these resistors would fail and so one of the 15v rails would disappear. This caused both the LF and HF amplifiers to swing hard one way, blowing the output transistors and both the drivers.

I advised the shop to get the remaining 12 cabinets to me ASAP so I could change the 100r resistors so the remaining cabinets wouldn’t suffer the same fate. The hotel refused to let the shop remove the remaining cabinets as they were "setting up for a conference and needed them”!!

On the day of the conference the shop "got the call" as the rest of the PA had stopped working and could they do something to help!!

This all happened at the time when RCF and Mackie were going through their “divorce” and due to the way they had set up the service arrangements the 12” woofer (or re-cone kit) was unobtainable, and as it’s not a standard chassis size nothing else fits the plastic cab. It was decided to wright-off all 20 failed cabinets.

…. All because a slightly undersized pair of resistors (and a client that didn't take advice)!!