Hi

I have built a vu meter with the LM3915 IC and i want to amplify my audio signal because its to low from my mp3 which is 300mV.
To how much should i amplify the voltage and why?
Is lm741 a good amplifier to use?
Is there any difference between using ±12v or 0v and 24v to supply the lm741 amplifier?

Thanks,

 

Hi
First, what did you set the reference voltage to? Now is a good time to post a schematic.

 

Is lm741 a good amplifier to use?

Probably not a good choice for your application.

Is there any difference between using ±12v or 0v and 24v to supply the lm741 amplifier?

Yes. LM741 is spec'ed to have a common mode input range to about 3V from the rails. If you use a single supply, the input couldn't go below around 3V. With dual supplies, oV would be supported. If you don't already have a negative supply, I'd use something else.

As mentioned, you should post a schematic so we don't have to guess about your circuit.

 

Vref is set to 10v

 

1: no need to amplify anything, just insert a voltage divider between REF-OUT and R-HI.
2: The LM741 is NOT a good amp to use in ANY situation. Send it to its grave and RIP.
3: not relevant.

Benta.

 

2: The LM741 is NOT a good amp to use in ANY situation. Send it to its grave and RIP.

It will work fine for many applications. I have dozens in my parts bins and find them still quite useful.

 

Vref is set to 10v

You don't need an amplifier. Just change your reference to 1.2 volts.