Linnin - I don't know what your problem is with the Subway amp, but it's quite disingenuous to make statements that are both disparaging to a product while being factually inaccurate about the representation between products. I don't care if you don't like the Subway amp, but I don't get your hostility on the topic, or towards a product, unless it's based on a lack of understanding of the technical basis behind all amp ratings.
Your statement about "Duty Cycle Voodoo Watts" does not take into account the fact that EVERY SINGLE class D amp (and most class AB/G/H amps as well) are also based on duty cycle. This would, based on what I know about the Fender Rumbles, include all of those as well. Just to clarify, I have no problem whatsoever with the Rumble amps, they are a great product from a great company.
There's a good reason for using duty cycle in all amps (including class D), because bass guitar signals are not, and can not be 100% duty cycle. That would equate to a signal with zero dynamics, and even the most demanding bass guitar application I am aware of includes at least 6dB of dynamics in any real world application. This would equate to a 25% duty cycle, which is twice as demanding as the typical 12.5% duty cycle used in pro audio and certification agency testing requirements. Given this, every amp that I am involved with is designed to well beyond 25% duty cycle and over >15 years of products I have not experienced any thermal or other shutdown protection issues with ANY of the products (including class AB and class D)
Just to clarify, the term continuous that is being used here is no more than a couple of seconds. "Continuous" is an incorrect, inaccurate term that was used. I have as much experience with the power module used in this amp as anybody else in the industry, I know for a FACT that this module under ANY condition can not deliver "1040 watts RMS" for more than a couple of seconds. The inverse time constant on the AC supply fuse alone (which can not be changed without voiding the UL recognition of the part) makes this an impossibility.
6.3A x 120V = 756VA (total power available at the "must carry" level of the fuse
756VA x .80% (@ 120V) = 604W (total audio power available on a continuous basis, assuming thermal shutdown doesn't occur)
Therefore, 1040 watts RMS can not ever be delivered on a continuous basis, but that's totally ok, because bass guitar is not a continuous signal.
Now, to see why duty cycle is used and why it's a valuable (and essential) tool, say we choose to use 25% as a threshold for acceptable duty cycle, the following modifier applies:
Take the limits of the AC fuse, and divide by the duty cycle, that would be the theoretical audio power available under 25% duty cycle conditions:
[604W/.25(%)] = 2416W RMS, the difference between the rated audio output and the continuous fused input are the boundary conditions.
Now, for reliability sake, we typically de-rate the fuse to 75% of rated values, so this becomes 604W x .75 = 453W maximum design input, resulting in 1812W audio out at 25% duty cycle. As long as rated output power at 25% duty cycle stays within the 1812W limits, the AC line fuse will be fine.
EVERY SINGLE part of the amplifier, the input common mode line filter, the input line frequency rectifier, the bridge switches, the power transformer, the high frequency rectifier, the class D bridge switches, the output integration filters all get analyzed in exactly the same way so that there are no weak links. This is not a specifically Mesa thing, it's not a Fender thing, it's not a Genz Benz thing or any other specific manufacturer thing. It's an industry thing, something that the ENTIRE industry has been practicing for at least 25 years that I know of, and it's to deliver a better quality, more reliable product to you players.
