A cold solder joint is grainy, because the solder didn't melt completely, therefore the connection isn't going to be reliable. Its likely to pull apart.
The proper way to solder is to make a strong mechanical joint first. Soldering to a lug means you need to strip the insulation back a bit, and wrap the bare wire around the lug through the hole, then twist it back so that by itself, the wire will remain in place.
*Then* solder over that.
Same for inline splices... strip back the insulation on both wires, overlay them about 1/2 way of what you stripped, and rotate them so they twist together. Then solder over that.
Rarely, if you "ball" the solder on the iron then drop it onto the wire or the lug, have you made a really good connection, unless you keep the iron there for a while, so that the base metal (the wire, lug, terminal, whatever) is hot enough to wick the solder into its surface.
I have seen many solder joints that look good, but whats underneath is not all that good. Doing it right is more work and a pain in the ass, but if you're wiring up 1500 solder joints in your studio, it would be nice not to have to revisit those joints for a few decades.
Also, for those who consider themselves "not so good solderers", using a top quality "silver solder" rather than the garbage from radio shack will make it that much easier. Normally silver solder is much thinner, thus melts easier, and silver solder has a lower melting temperature than rosin core lead/tin solder, so I'd give that a whirl.
I use radio shack solder for temporary stuff - like wiring experiments for fuel injection stuff on
my workbench, audio circuits I'm just wiring up to play with, but anything thats final, important, or serious, I use silver solder all the way.
If you're just going to wire up a few things, a radio shack soldering iron is a cheap way to go. But do know that their temperature fluctates wildly, and for $9 you shouldn't be too suprised. If you're going to wire up your studio, maybe 10 patch bays per side with 48 jacks with 3 terminals a piece, that would be 1440 solder joints right there, plus any patch cords you want to make, I'd recommend spending a few dollars and buying a weller variable temperature soldering iron. They are more comfortable to work with, as the handle is better insulated, the tips are of better quality than the ratshack stuff, and its a professional tool. I've seen lower end "good stuff" weller soldering irons mail order in the $50ish range. Its a tool you can use for decades too. I do use ratshack soldering irons sometimes for things that aren't important, they are also good for tossing in a tool bag to solder at a friends, because for $9 its okay to break them
But they do burn out after a while and the handles get too hot for my tastes.
In fact, I just finished last weekend the wiring harness for my F350 crewcab. Bumper to bumper, there are 76 connectors, 120 splices, and somewhere around 5000 solder joints total. Silver solder/weller all the way.
Anyway, hope that helps.
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