DDS filters

I can use an Efinix FPGA and a bunch of cheap fast DACs to make some
DDS clock sources, specifically four. The pain is the lowpass filter.

Mini-Circuits and other folks make nice surface-mount lowpass filters,
but they are most all in the GHz range. I want maybe 25 MHz. You'd
think there would be a market for packaged MHz-range lowpsss filters.

It's worth pushing the DAC rate as high as possible to simplify the
lowpass filter. Stay far away from Nyquist.