"No Spam" wrote in message
...
On Sun, 21 Dec 2008 11:45:51 -0800, Tom, N3IJ wrote:

Can anyone suggest a source of a circuit or kit for a mono amp to
increase my laptop's headphone output level to line level?

As a starting point, it would be helpful just to learn what these levels
are. I want to drive a line-level transceiver input for digital hamming.

Any suggestions would be appreciated.

You have an impedance mis-match. Use a radioshack xformer with the 8ohm
side on the headphones jack and the 5k output to the line level. You will
need a pad or simply a pot after that.

An impedance mismatch in this case only equates to a possible power loss.
The transformer (I think RS only offers a 600:600 ohm line transformer)
is good because it offers some isolation between the equipment.

Is your laptop audio stereo or mono? You'll have to take that into
consideration,
since you don't want to short on of the channels using a mono plug.
If stereo, you will need to work up some sort of passive mixer
(resistors would do it) to combine the two channels.

Pete