SET DIY compared to Wavelength or Commercial Brand

You are correct that it is relatively easy to build an SET amp. Plans and parts are readily available. The low parts count makes them fairly simple to construct and you will probably end up with a good sounding amp saving a lot of money in the process. Building a great sounding SET is a different matter.

Wavelength is also basically a DIY operation, it is just that the "yourself" in that operation, Gordon Rankin, has been doing it for many years. Since that is what he does, he has the chance to experiment with many different designs and parts. I would venture to guess that for every itteration that he puts on the market there are many, many more that he has rejected.

As for jobbing out a DIY, most kit companies offer their amps as assembled units. Exemplar Audio will assemble and/or modify a bottlehead SET amp for you. I think that kind of defeats the purpose of DIY but you will have a very nice sounding amp at a reasonable price. However, you can have a Wavelength Duetto on the used market for about what you would have in the bottlehead. At that point it is a matter of taste.

I agree with TWL that 8 watts should be plenty, which BTW is what a Wavelength Duetto and a host of other 300B SET amps produce.

Richard, I am really not trying to sound like a "smart-ass", but that is sort of like asking you,"If a meal is so easy to prepare, why hire a chef?"

The fact is that experts can do things better than novices. If you can take a design that is known to be good, add in the high-quality parts in the right places, with the right values, and have an expert assembler build it for you, you may have a product that is competitive or maybe better than some commercial products. The thing that is on the DIY side, is that no profit markups have to be considered, so you can add better parts for the same money as a commercial unit, or less even. I do alot of DIY, and it can be good or it can be a bust. You are going to have a hard time topping a Wavelength. They are not beginners.

Regarding how many SET watts will equal your 42 Push-Pull watts, the answer is 42. However, you will realistically need no more than 16 watts, and probably less. An 8 watt 300B amp would probably be more than sufficient for you, on your 100db efficient speakers.