Hello,
I am dreaming about 2.1 amplifier project. The main reason I am starting new thread is that I can not find any preamplifier circuits for 2.1 configuration. Do you have any suggestions with that kind of configuration with 2 channels stereo input and 3 channels output (one for subwoofer and left/right channel with tone control, LPF for subwoofer channel).
Here is active cross over circuit for 2.1 configuration:

My question is: Is this circuit works as a preamplifier too? Or I need to make preamplifier circuit after this crossover circuit? I am confused.
What block sequence should be for this kind of amplifier configuration - Power supply - preamp - tone control - power amplifier?

 

Depends on the signal levels at the inputs and outputs of your design. With standard stereo line level inputs you want the output of your circuit the same level as the inputs.
Power supply - preamp - tone control - power amplifier. That will work. As I was saying above you want to keep the signal level coming out of the Tone control around the same level as the signal going in.
Steve G

 

Preamplifiers used to have a high gain amp for the magnetic phono input (mV signals), but that's long gone.
Now preamplifiers mainly provide volume and tone control, along with input source selection, with no significant added gain (at maximum volume) between input and output.

 

When you run the numbers, what do you come up with for the passband gain of each channel filter (before the variable stage in the sub channel)?

ak