Will This Pre-Amp Circuit Work

[benproiii]

i want to plug my computer and or ipod into the preamp and it will increase the volume to the same line level of a cd player or dvd player's audio out which can be plugged into my stereo. without a preamp with my amp and my computer up all way the sound is not even that loud. ( i got the opamp BA15218 from a broken stereo it seems the be similar to the ne5532) i attached a picture of the circuit

[abraxalito]

No, it doesn't look like it will work.

Overall there's attenuation on the iPod input of 33dB and the opamp gain is 27dB. So the best it can do is make your iPod half as loud as when its not in circuit. Your input 1uF is the wrong way around and your output pot seems redundant (as well as seemingly connected backwards). The 1uF output coupling cap would do well it be more like 100uF. The 27dB gain will probably prove inadequate for a mic input.

[benproiii]

will this modified circuit work better

[abraxalito]

Its definitely an improvement

I'm a bit dubious about your initial premises - you say your computer doesn't go loud enough - but sound cards put out similar levels to CD players (1-2VRMS) in my experience.

On to your revised circuit - why the input attenuator then opamp gain? Why not reduce the attenuation (like have no attenuation) then have reduced opamp gain? Loss then gain is just a recipe for increased noise and distortion, it gives no advantages. I'd suggest having the volume control on the input, not the output. Your coupling caps (0.22uF, 1uF) still look rather too low. But its coming along...

[paulb]

You should probably read this, or other tutorials on designing with opamps:
HeadWize - Project: Designing an Opamp Headphone Amplifier (A HeadWize Design Series Paper)

[benproiii]

i should remove R1 and make C1 a 10uf non polarized

[abraxalito]

No, remove R1 and R2 and replace them with the volume pot, wiper to C1. Reverse polarity on C1 and increase its value to 1uF. Reduce 22k to 4k7, reduce 10k on output to 100R, increase 1uF to 100uF and put +ve to left. Add a resistor of 100k where the volume pot used to be. That oughta do it.

[benproiii]

what do u mean by but ve+ on left

[abraxalito]

I was talking about the new 100uF output coupling capacitor - connect its +ve terminal to the opamp output (the left side of the cap on the schematic). Currently you don't show polarisation on that cap, perhaps because its only 1uF.

[benproiii]

modified again