A excellent Pre-amp

[badboy6120]

Hi

Could anybody help me to build a excellent pre-amp for my sub woofer?

I'm using this circuit as my sub's amp:
230W / 400W Mosfet Amplifier



and this circuit as my sub's low pass filter:



I'm getting a excellent sound of my sub when I connect it to my PC but when I use different audio sources like DVD player or TV and etc It doesn't have the same sound when I use it with my computer
I want a pre-amp or even an low power amp so I can match this sub's amp with any kind of audio sources
I used LM386 but it has some DC voltage in its output
So if anyone could help me with it I'll appreciate it

[badboy6120]

Anyone?????

[Original Burnedfingers]

Your PC has gain that you can control/volume control.

DVD or TV is going to the crossover? If so employ a preamp. Hook your DVD

or TV output to a preamp and the output of the preamp to your crossover.

[badboy6120]

Your PC has gain that you can control/volume control.

DVD or TV is going to the crossover? If so employ a preamp. Hook your DVD

or TV output to a preamp and the output of the preamp to your crossover.

thanks 6BG6GA
but as I said before I'm looking for this pre-amp and I need some info about it like its schematic

[Mooly]

Why not add gain to the first opamp in the filter like this.

Use say 10K for the feedback resistor and select the other resistor to give the gain required. With TL072 (FET) there should be no DC offset problems so I haven't shown a cap in series with the other resistor. The switch is just to switch between original gain (x1) and the new gain. Or use a pot to set the gain.

[badboy6120]

Why not add gain to the first opamp in the filter like this.

Use say 10K for the feedback resistor and select the other resistor to give the gain required. With TL072 (FET) there should be no DC offset problems so I haven't shown a cap in series with the other resistor. The switch is just to switch between original gain (x1) and the new gain. Or use a pot to set the gain.

Thanks a lot
I'm gonna check that

[Mooly]

Your welcome.

[badboy6120]

Hi Mooly

I tried what you told me about increasing the first op_amp's gain
and here's the schematic that I used :


But when I turn the pot to increase the gain (to around 2) the out put sound changes to a loud continuous voice (like Hummmmmmmmm)

I also increase the gain to around 5 but it makes it worse

What shall I do now????
Thank you so much

[Mooly]

Is the opamp running on dual (split supplies) ? I assumed it is but better check.

If so it should work... if not you need a cap in series with the pot.

[badboy6120]

Yes the supply is +/-12Vdc
how much cap do I need?