My CD player works fine with my full-duplex sound card. When I want to play it through the realtime Lake convolver, there is no signal at the convolver. What is wrong?

The duplex sound card has an input and an output channel. If the CD player is connected to the sound card inside the PC with the special small plug, it is connected to the output channel, because the aim of the connection is playing.

For convolution, which is an unusual application for that configuration, the CD signal is required on the input channel of the card, to be convolved and thereafter send to the output channel.

You need to connect the CD player output with the sound card input. You can use the external line-in plug of the sound card. If your CD has no suitable line-out for this, you may need an additional simplex sound card to connect the CD to internally, and then connect this card's line-out to the duplex card's line-in.

Note that you can run the convolver as well with 2 simplex cards instead of 1 duplex card.
Again, the CD player must be connected to the 'input card' while loudspeakers or headphones must be plugged into the 'output card'. If you connect 'line-out" of the input card with 'line-in" of the output card by a short cable, you can then run this configuation in various modes without changing the wire links, just by checking the mixer channels of Window's volume control (also available in EASE EARS, menu Tools/Volume Control).

The same holds for any other streaming audio input sources like PC TV cards, PC radio cards, or microphones. Any of those signals must be directed to the duplex card line-in for convolution. If you have an additional simplex soundcard, you can use this card as mixer or channel selector, before you transmit the resulting audio signal to the duplex input plug.

If you are not yet experienced with the Windows mixer, start the standard Windows volume control and experiment with the various sliders and switches available separately for all input and output channels for all sound cards installed on your PC (SndVol32.exe under \Windows\). Make sure your soundcards are properly installed under the device manager, and especially the duplex card is set to full duplex mode.