Re: PSA: Blow it out yer amps!
Were you involved with the DPC750/1000?
Who wants to know?
Just kidding. No I was not directly involved in the design but later when I got involved with product management for all power amps, it became one of my product responsibilities, (around the time of the DPC 1000). But I know a lot of the history and drama surrounding Peavey's long investment in class D technology.
Even though Class D is not really digital, at Peavey it was engineered by the digital group while all the other amplifiers were engineered by the analog group. To put it as kindly as possible there was an in house rivalry between the digital and analog groups so they didn't play together well... the decades of amp experience and judgement resident in the analog group did not get drawn upon in the early class D amps, some of which were hand grenades.
When I first took over the DPC program and became the official cheerleader I was surprised by a few things I learned about it. Apparently the DPC engineers thought it was a good idea to fold back the voltage gain when it got too hot. They were told that it was unacceptable to shut down, so this was their solution. Of course in live sound use, this was almost worse. These amps were popular for use in monitor rigs, and when the gain dropped drown, they would just turn it up again, then sometime later when the amp cooled down, the gain would jump back up and feedback city. I had them stop that nonsense immediately (instead I had them switch the fan to higher speed when hot but leave the gain alone).
Yes, I was a supporter of the 1u configuration. It was never going to be a cheap amp, so it needed some sex appeal. Despite the digital boys claiming they could make it cheaper, I had an open engineering project to make class D power module to use with top-box powered mixers. After a few years of piddling on the bench it never hit the price targets.
My idea to combine 4 CH of DPC with a 2x4 digital crossover was based on another quirk of the DPC topology. Without getting into too much of the technology the DPC performed the PWM by phase shifting one square wave relative to a second square wave. In a 4 channel power amp I could use the one master 1kW square wave, and then draw the 4 outputs in any combination of power that added up to 1kW. Keep in mind this was around 20 years ago so even the digital crossover was not a mature technology back then. This would have been a champagne product, for a beer and peanuts distribution, so not a very good match. It took me a while to figure that out, but after I did I had some successful products there.
Big on bang for the buck, light on sizzle was the recipe for success.
JR
