"Few of the American amplifier builder know anything about RF design"
absolutely true 148,
many just copy davemade amps ( swing boxes ) that never were designed for cleanliness or running on stock voltage, the design is nothing like any conventionally designed amp from helge grandbergs motorola application notes or the toshiba datasheet,
the amps were designed to win keydowns against conventional amps which they will do, a 2pill dave style amp WILL whoop 4pill in a keydown,
datasheet nuthuggers are armed with a little info but not enough, toshiba datasheets only tell half the story, look at other transistors that show output & imd at different supply voltages,
Dave is smart, he understood vcc vs load impedance years ago as anybody that builds tube amps should understand, he knew doubling your supply voltage quadruples your output power when optimally load matched so a moderate increase in vcc can yield much more power,
as you raise vcc optimum load impedance increases, change class & optimal load impedance changes,
dave knew that you can run transistors at higher vcc and load impedance at a reduced duty cycle to get more power without exceeding maximum device current or maximum device dissipation, how much more power ? a hell of a lot more than the datasheet tells us,
that its not just current but current x time that smokes the device,
a fuse will handle many times its amp rating if you pulse current through it so reducing the time the device is turned by going class C allows the gold wires that connect the tabs to the die under the beryllium oxide cap that coined the term pills to handle more current than the datasheet tells us,
you can push a device into deep class C by using negative voltage biasing to reduce on time even further than a grounded base type class C,
a few 55 built amps used a pp3 battery hidden inside the amp to get the negative biasing,
Dave understood what the datasheet did and more importantly what it did not tell you, and that absolute ratings are higher than what the datasheet tells us if reliability and imd are of no concern,
you don't build the same engine for a drag race if you want to race round a track for many laps and a different engine again if you want to go shopping or are the slightest bit concerned about emissions, there's no over fuelling to cool cylinder temps in your shopping trolly,
he built class C drag racing amps with the required for keydowns 2sc2879's that ran on 21v or a tad higher ( 18v max on datasheet ) with transformer turns ratios and tuning ( oh the top secret tuning on 6pills & upwards
) and larger different mix ferrite thicker silver plated teflon wire a low loss solid groundplane to cut as much volt drop as practical, homebrew tuning capacitors,
it worked, even a 2pill with fixed interger turns ratios would whoop a conventional 4x2879, taking on anybody in the same pill class that was using conventional design amps was no problem,
i have keyed my 2x2879 on just 18v against hot rodded kl500's on stock volts many times and never lost a keydown,
keydown style amps are far from optimal if all you have is stock voltage, they are very inefficient on stock voltage sucking more current per watt output than a conventional amp with double the number of 2879's, been class C they also sound like **** on SSB and rough on AM,
the copycats like xfarce & fatboy sell you the same amp for stock voltage or keydown use, they also put SSB delays on class C amps which is stupid & proves they don't understand much about how amplifiers work.
many folk think that because their amp is class C it must be more efficient than a class AB amp,
if both are correctly designed for the same supply voltage that's true, but its far from true when the class C amp is designed for 21v+ and running on stock voltage,
an interesting read for the folk who don't believe it.
https://forums.qrz.com/index.php?thread ... ha.248732/