I have done several Class-D amplifier designs ranging in power from between 75W and 1000W of output power. My present Amplifier topologies are capable of output power as high as 2000W into 2Ω, although no one has requested that I build an amplifier at this high a power level as of yet. I have other Class-D topologies capable of much greater output power and output voltage, they are currently under development at this time.
There is much that still needs to be done in the whole field of class-D audio amplifiers to allow them to approach the audio performance of the very best linear amplifier designs. I’m excited to have the opportunity in the coming years, to further refine the state of the art with these switching amps.
I’m just going to come right out and say it: I really love the performance I’ve been able to get out of the various linear amplifier designs that I have done in the past. Unfortunately, the parts count is much higher on a linear amplifier than that of it’s class-D counterpart. I fear that my days of designing Class-AB, Class-G, and Class-H linear amplifiers is very likely behind me: From a cost standpoint it’s very hard for most companies to justify the bill of material cost of a linear amplifier. It’s also hard to argue the very desirable aspects of class-D amplifiers coupled with switching power supplies as being much lighter and more efficient than a completely linear design.
At Mackie/Loud I developed the original series of power amplifiers from around 1996 to 1998: The M-1400 (which came 1st), followed by the M-2600 and finally the M-800 amplifier, all class-AB designs. In 2006 I designed the FR Millennium line that gave the market the M-2000, M-3000, and M-4000 stereo power amplifiers. These amplifiers exhibited some of the very lowest distortion numbers over the entire pro audio market, beating almost every competitor out-there by an order of magnitude or better. They also displayed a very low noise floor, very fast slewing, and very benign behavior into and out of clipping as well as having very stable performance into reactive loading.
The power stages of all of the Mackie amplifiers were quite linear without negative feedback ,which contributed to their low distortion characteristics. The M-2000 (a two rail class-H design) and the M-3000 and M-4000 (3-rail class-H designs) utilized an adaptive slew Class-H stage which only switched as fast as the audio signal required of the Switcher riding above. This variable speed behavior greatly reduces higher order switch induced harmonic distortion on the output line. To my knowledge, no one else ever did this with a Class-H switching stage: In retrospect, I suppose I should have patented the idea and topology!
Below are a few examples of my amplifier work:
My Latest creation (as of 2015) is the TKO-1000W and 500W amps I just completed for Keen Ocean (Class-D):
The Mackie M-2000, M-3000 & M-4000 (with the insides of the M-4000 shown):
Mackie M-1400 and M2600:
Mackie M-800:
