how can I make a power supply with a fully smooth output.

Hi;

I built a pre amp with LA3161 (please see the attachment). Basically it’s working fine, but it generate considerable level of noise. I set power (12V) with 230-12v transformer, bridge rectifier and smoothing cap (1000mfd). Then I feed power with a 12V battery, and found it was working fine with battery power. So please let me know how can I make a power supply with a fully smooth output.

more smoothing caps, have a cap after the rectifier, and then before and after the regulator, this works well for me on 3.3v devices and i get very stable outputs.

Have you measured the output voltage of your P/S? Have you employed any regulation for a stable 12V supply output?

It would be helpful if you posted a schematic of the supply you built and the desired/expected output.

Is there anything else hanging on the output of your power supply? With the cap you have got (1000uF) and the part taking 8mA max, you should end up with a ripple of 80mV and the amp should have enough power supply rejection ratio to remove this. If there is any other load on the output of the power supply (LEDs and stuff) then your ripple will go up and this will feed through to the output. Also, what do you class as noise? Is it hiss, crackle or hum (wasn't that a U2 album... or a breakfast cereal?)

Please describe the noise. Hum? Hiss? I guess it is hum from the power supply or from unshielded input cables.

Why are you making a NAB preamp for an old tape head? Do you still play old cassette tapes?

You need a regulator such as the 7812 or the LM317T.