Building the DDS-60
The DDS-60 kit uses surface mount technology and can be a challenge to build if, like me, you haven't used SMT before. There's a lot of advice online about SMT construction so I won't go into it much here. You need a good magnifying lamp, a fine tip on your soldering iron, some tweezers and a "third hand" type thing to hold the board while you're working on it. You'll probably need solder wick to pull excess solder away when you form accidental bridges. The wick is a more gentle and precise method than using a pneumatic solder sucker tool.
I have to admit that it seemed pretty daunting when I started but it got easier as I progressed. The instructions say to start with the AD9851 chip. The good news is that it is the most difficult part. The pins are 0.65 mm apart!
If you really don't want to tackle this then the DDS-60 site has a couple of other options. You can buy it already assembled and or make use of a service someone provides to put the SMT components on the board for you to finish off.
I managed to break the little trimpot that adjusts the output level so I replaced it with a 220 ohm fixed resistor. That seems to be about the right value because I'm getting about 4 volts peak to peak output. Much more than that and it would probably start distorting with clipping on the peaks.
Putting it all together
The RBBB is also a kit but with conventional components and very simple to assemble.
I assembled it all on a piece of Veroboard / stripboard and mounted the whole thing in a metal box with dimensions 120 x 85 x 38 mm ( 4 3/4 x 3 1/4 x 1 1/2 in) that I bought from the arts and craft store called Michaels. Unfortunately they don't seem to sell the boxes online.
You'll need some header type connectors. I got these from Modern Device. Here's the 8 pin for the DDS-60 and a couple of 40 pins to chop off to size for the RBBB to plug into. You don't really need the 40 pin headers if you're prepared to solder the RBBB into your main board. The connectors do tend to make the RBBB sit a little unnaturally high above the board but, since my box is big enough, I like the ability to remove the RBBB if necessary.
I don't think there is anything particularly critical about the construction. As you can see from the photos, I'm no mechanical engineer. I wasn't very successful in trying to cut a neat clean cut opening for the display with my Adel nibbling tool. The whole thing could be made much smaller and neater by someone with better skills and tools. I choose the type of push buttons because they are easy to mount simply by drilling a hole but small keypad type buttons would be more attractive. It all works well which of course is the main thing to us hams