[sdiy] Balanced/unbalanced inputs?

[DTK]

> To use an unbalanced line into a balanced input, you
> could try attaching the unbalanced line to one of the
> balanced lines, and ground the other side. This may
> work, but there's a problem: balanced inputs tend to
> be higher levels (+4 dBv) than the unbalanced ones
> (-10dBv).
>
> Or you could go to Radio Shack and buy a
> unbalanced-to-balanced adapter for about $20.

So If my instruments have unbalanced output, I can't use them with a mixer
that has balanced inputs unless I 1) modify the cable or 2) buy an adapter?

How can I tell what type of output my instruments have? I assume they're all
unbalanced, but I don't know how to check. It's not it the manuals...