Jump to content
Electronics-Lab.com Community

Audio amplification question


wado1942

Recommended Posts

Hello.  I'm very new to electronics and have myself in an odd situation.
I'm trying to design a simple audio amplifier to drive a VU meter based on the 4739 dual opamp because I have a bunch of them.
I've attached a crude scheme below.

audioscheme.gif


What's happening is I get an audio signal, but it's always unity gain regardless of the pot position.  I know the amplifier is working because my first version ran on a 9V battery and the output was weak and distorted.  When I switched to a +-12V power supply, the signal got stronger and clearer.  If I touch anything in the feedback loop, I hear the interference.  I tried reading about op amp design but from everything I've read, I should be getting 0-10x gain.

Like I said, I'm pretty clueless so any help will be much appreciated.

Link to comment
Share on other sites


Thanks for the quick replies everybody.
I actually tried running into the inverting input and got nothing out of it.  It didn't make sense to have a 1K resistor feeding into the non-inverting input but since I didn't get a signal, I tried it the way I showed in the scheme.  Perhaps my ground on the non-inverting input was poor.  I'll give it another shot.

Thanks again,  I was racking my brain yesterday over this.

Link to comment
Share on other sites

Well the inverting amp configuration works like a charm so I'm going with that.  My next challenge is adding a -10dB switch.  Any suggestions?  I was thinking a resistor to shunt part of the input signal to ground but I wouldn't know how to calculate it.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
  • Create New...