[Moved]: amplifier lm3886 sounds slowly

[julian403]

Hi, I made an amplifier with LM3886 but it sounds slowly, more than without the amplifier. The circuit I made it's from texas datasheet.



For RM I used 3k9, for Rf1 I used 22K , and for Ci I used 47 µF electrolitic. Maybe It's because one of this component's value.

bye.

 

[barry]

Re: amplifier lm3886 sounds slowly

I presume when you say it "sounds slowly" you mean it has low output? What are your supply voltages? You need to have > 0.5mA flowing through RM for the mute function to be off.

 

[julian403]

Re: amplifier lm3886 sounds slowly

Yes, it has very low output. The supply voltage is +- 34 V. indeed, I put a speaker 3W and sounds slowly

 

[barry]

Re: amplifier lm3886 sounds slowly

Yes, it has low output. The supply voltage is +- 34 V.

And you have the Rm resistor connected to -34?

 

[julian403]

Re: amplifier lm3886 sounds slowly

yes, from the pin 8 to -34V. I think it can be because the value of Rf1, Ri and Ci. But I use the value that datasheet says. Following datasheet

Ri= Rf/ (Av-1)

so with Ri=1k , Rf= 22-k , the voltage gain is Av=23.

- - - Updated - - -

I fixed, i change R1 from 1 Kohms to 100 ohms. But another things, if higher the potentiometer higher power output ?

 

[barry]

Re: amplifier lm3886 sounds slowly

yes, from the pin 8 to -34V. I think it can be because the value of Rf1, Ri and Ci. But I use the value that datasheet says. Following datasheet

Ri= Rf/ (Av-1)

so with Ri=1k , Rf= 22-k , the voltage gain is Av=23.

- - - Updated - - -

I fixed, i change R1 from 1 Kohms to 100 ohms. But another things, if higher the potentiometer higher power output ?

You've now got a gain of 221.

The value of Rm has nothing to do with the other components-it simply sets the current at pin 8.

Changing the potentiometer value will have little effect, unless you go to extremes. Stupid question, but do you have it turned all the way to the end?

 

[Audioguru]

What is the low input level from? A microphone? Then it needs a preamp so that the power amp can have a gain that is only 23 times for very low distortion.
Now that you increased its gain 10 times then you also increased its distortion and noise 10 times.