[sdiy] Using SSM2164 in stereo

[David G. Dixon]

> But a true virtual current source does not need to be limited, since
> it is going to supply a constant (or controlled) current, right?

Quite right.  And it would supply that current regardless of the resistor
appended to it, unless of course the resistor pushed the source voltage
right to the rail, in which case one would exceed the "compliance" of the
current source.  Probably another reason not to put one on.
 
> Don't resistors only limit current from voltage sources? 

Yes.

> With current
> sources, we have U = IR, so that we're 'limiting' voltage. I
> understand that the losses in current would be due to the resistor
> heating up which is not a very efficient way of limiting current.

Hot resistors don't lose current.  They lose energy in the form of heat.
The electrons lose potential, but the same number of them flow.