Volume control for LM386












3














For some context, see my earlier question:
Ceramic capacitor value for an LM386N project



What I learned is that the 10k potentiometer on pin 3 (Vin) forms a voltage divider. When I carefully dial it, I find a spot where I get clean audio (the 10k pot is then at ~ 500 Ω). This is the same with the ready-made breakout board that I used for comparison.



Now the point of not using the ready made module was that I wanted to add a volume control. Apparently scaling Vin is not how one supposed to do that. If I go up or down from the spot where the audio is good, I get distortions, but never a quieter signal.



I also tried to add a pot between pin 1 and the ceramic capacitor that goes to pin 8. The datasheet has three examples:




  • gain 20: by default there is a 1.35 kΩ resistor

  • gain 50: use a 1.2 kΩ resistor

  • gain 200: use no resistor


I only had a 2k potentiometer and when I dial it from 0 Ω up, the signal gets a bit quieter, but I can't get it down to silence. If I remove the circuit between pin 1 and 8 to operate at gain 20, the output is pretty quiet though.



I searched the Internet quite a bit, and I probably miss something obvious. It would be awesome to get some pointers.






lm386 volume







share|improve this question





























    3














    For some context, see my earlier question:
    Ceramic capacitor value for an LM386N project



    What I learned is that the 10k potentiometer on pin 3 (Vin) forms a voltage divider. When I carefully dial it, I find a spot where I get clean audio (the 10k pot is then at ~ 500 Ω). This is the same with the ready-made breakout board that I used for comparison.



    Now the point of not using the ready made module was that I wanted to add a volume control. Apparently scaling Vin is not how one supposed to do that. If I go up or down from the spot where the audio is good, I get distortions, but never a quieter signal.



    I also tried to add a pot between pin 1 and the ceramic capacitor that goes to pin 8. The datasheet has three examples:




    • gain 20: by default there is a 1.35 kΩ resistor

    • gain 50: use a 1.2 kΩ resistor

    • gain 200: use no resistor


    I only had a 2k potentiometer and when I dial it from 0 Ω up, the signal gets a bit quieter, but I can't get it down to silence. If I remove the circuit between pin 1 and 8 to operate at gain 20, the output is pretty quiet though.



    I searched the Internet quite a bit, and I probably miss something obvious. It would be awesome to get some pointers.






    lm386 volume







    share|improve this question



























      3












      3








      3







      For some context, see my earlier question:
      Ceramic capacitor value for an LM386N project



      What I learned is that the 10k potentiometer on pin 3 (Vin) forms a voltage divider. When I carefully dial it, I find a spot where I get clean audio (the 10k pot is then at ~ 500 Ω). This is the same with the ready-made breakout board that I used for comparison.



      Now the point of not using the ready made module was that I wanted to add a volume control. Apparently scaling Vin is not how one supposed to do that. If I go up or down from the spot where the audio is good, I get distortions, but never a quieter signal.



      I also tried to add a pot between pin 1 and the ceramic capacitor that goes to pin 8. The datasheet has three examples:




      • gain 20: by default there is a 1.35 kΩ resistor

      • gain 50: use a 1.2 kΩ resistor

      • gain 200: use no resistor


      I only had a 2k potentiometer and when I dial it from 0 Ω up, the signal gets a bit quieter, but I can't get it down to silence. If I remove the circuit between pin 1 and 8 to operate at gain 20, the output is pretty quiet though.



      I searched the Internet quite a bit, and I probably miss something obvious. It would be awesome to get some pointers.






      lm386 volume







      share|improve this question















      For some context, see my earlier question:
      Ceramic capacitor value for an LM386N project



      What I learned is that the 10k potentiometer on pin 3 (Vin) forms a voltage divider. When I carefully dial it, I find a spot where I get clean audio (the 10k pot is then at ~ 500 Ω). This is the same with the ready-made breakout board that I used for comparison.



      Now the point of not using the ready made module was that I wanted to add a volume control. Apparently scaling Vin is not how one supposed to do that. If I go up or down from the spot where the audio is good, I get distortions, but never a quieter signal.



      I also tried to add a pot between pin 1 and the ceramic capacitor that goes to pin 8. The datasheet has three examples:




      • gain 20: by default there is a 1.35 kΩ resistor

      • gain 50: use a 1.2 kΩ resistor

      • gain 200: use no resistor


      I only had a 2k potentiometer and when I dial it from 0 Ω up, the signal gets a bit quieter, but I can't get it down to silence. If I remove the circuit between pin 1 and 8 to operate at gain 20, the output is pretty quiet though.



      I searched the Internet quite a bit, and I probably miss something obvious. It would be awesome to get some pointers.






      lm386 volume




      lm386 volume






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited yesterday









      Peter Mortensen

      1,60031422




      1,60031422










      asked 2 days ago









      ensonicensonic

      13016




      13016






















          2 Answers
          2






          active

          oldest

          votes


















          5














          You probably used a linear (B) taper pot. For audio you want an (A) log taper pot, so your 500 ohms will be about 25% of full electrical rotation, not 5%.



          Image from this site.



          enter image description here






          share|improve this answer





















          • I meassured my pot an it is indeed lin, but that does not explain that it goes from noise to audio to noise. With a log one the range is easier to adjust, but I don't believe that the place where one should add the pot is where one can adjust the volume. It sounds like it should work, but then I should be able to control the volume a bit at least, right?
            – ensonic
            2 days ago



















          3















          • Gain of 20 is too quiet

          • Gain of 200 is too distorted and can't turn it down to get quiet.


          Choose Gain =50 with 1.2k in series with cap



          Pots do not have a 60dB dynamic range so they usually gang 2 pots {pre-amp gain & power amp gain} to get 30dB in each.





          Solution



          Ganged Pot



          schematic





          But as Dave say's that needs to be an audio log pot.



          enter image description here






          share|improve this answer























          • You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
            – Sunnyskyguy EE75
            2 days ago












          • Isn't this very impractical to adjust volume using 2 potentiometers?
            – ensonic
            2 days ago






          • 1




            They make stereo ganged pots which you can gang to 4 but like said in integrated receivers they gang preamp gain with power amp gain or something better like digital pots. (not for newbies)
            – Sunnyskyguy EE75
            2 days ago













          Your Answer





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          2 Answers
          2






          active

          oldest

          votes








          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          5














          You probably used a linear (B) taper pot. For audio you want an (A) log taper pot, so your 500 ohms will be about 25% of full electrical rotation, not 5%.



          Image from this site.



          enter image description here






          share|improve this answer





















          • I meassured my pot an it is indeed lin, but that does not explain that it goes from noise to audio to noise. With a log one the range is easier to adjust, but I don't believe that the place where one should add the pot is where one can adjust the volume. It sounds like it should work, but then I should be able to control the volume a bit at least, right?
            – ensonic
            2 days ago
















          5














          You probably used a linear (B) taper pot. For audio you want an (A) log taper pot, so your 500 ohms will be about 25% of full electrical rotation, not 5%.



          Image from this site.



          enter image description here






          share|improve this answer





















          • I meassured my pot an it is indeed lin, but that does not explain that it goes from noise to audio to noise. With a log one the range is easier to adjust, but I don't believe that the place where one should add the pot is where one can adjust the volume. It sounds like it should work, but then I should be able to control the volume a bit at least, right?
            – ensonic
            2 days ago














          5












          5








          5






          You probably used a linear (B) taper pot. For audio you want an (A) log taper pot, so your 500 ohms will be about 25% of full electrical rotation, not 5%.



          Image from this site.



          enter image description here






          share|improve this answer












          You probably used a linear (B) taper pot. For audio you want an (A) log taper pot, so your 500 ohms will be about 25% of full electrical rotation, not 5%.



          Image from this site.



          enter image description here







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 2 days ago









          Spehro PefhanySpehro Pefhany

          204k4151408




          204k4151408












          • I meassured my pot an it is indeed lin, but that does not explain that it goes from noise to audio to noise. With a log one the range is easier to adjust, but I don't believe that the place where one should add the pot is where one can adjust the volume. It sounds like it should work, but then I should be able to control the volume a bit at least, right?
            – ensonic
            2 days ago


















          • I meassured my pot an it is indeed lin, but that does not explain that it goes from noise to audio to noise. With a log one the range is easier to adjust, but I don't believe that the place where one should add the pot is where one can adjust the volume. It sounds like it should work, but then I should be able to control the volume a bit at least, right?
            – ensonic
            2 days ago
















          I meassured my pot an it is indeed lin, but that does not explain that it goes from noise to audio to noise. With a log one the range is easier to adjust, but I don't believe that the place where one should add the pot is where one can adjust the volume. It sounds like it should work, but then I should be able to control the volume a bit at least, right?
          – ensonic
          2 days ago




          I meassured my pot an it is indeed lin, but that does not explain that it goes from noise to audio to noise. With a log one the range is easier to adjust, but I don't believe that the place where one should add the pot is where one can adjust the volume. It sounds like it should work, but then I should be able to control the volume a bit at least, right?
          – ensonic
          2 days ago













          3















          • Gain of 20 is too quiet

          • Gain of 200 is too distorted and can't turn it down to get quiet.


          Choose Gain =50 with 1.2k in series with cap



          Pots do not have a 60dB dynamic range so they usually gang 2 pots {pre-amp gain & power amp gain} to get 30dB in each.





          Solution



          Ganged Pot



          schematic





          But as Dave say's that needs to be an audio log pot.



          enter image description here






          share|improve this answer























          • You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
            – Sunnyskyguy EE75
            2 days ago












          • Isn't this very impractical to adjust volume using 2 potentiometers?
            – ensonic
            2 days ago






          • 1




            They make stereo ganged pots which you can gang to 4 but like said in integrated receivers they gang preamp gain with power amp gain or something better like digital pots. (not for newbies)
            – Sunnyskyguy EE75
            2 days ago


















          3















          • Gain of 20 is too quiet

          • Gain of 200 is too distorted and can't turn it down to get quiet.


          Choose Gain =50 with 1.2k in series with cap



          Pots do not have a 60dB dynamic range so they usually gang 2 pots {pre-amp gain & power amp gain} to get 30dB in each.





          Solution



          Ganged Pot



          schematic





          But as Dave say's that needs to be an audio log pot.



          enter image description here






          share|improve this answer























          • You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
            – Sunnyskyguy EE75
            2 days ago












          • Isn't this very impractical to adjust volume using 2 potentiometers?
            – ensonic
            2 days ago






          • 1




            They make stereo ganged pots which you can gang to 4 but like said in integrated receivers they gang preamp gain with power amp gain or something better like digital pots. (not for newbies)
            – Sunnyskyguy EE75
            2 days ago
















          3












          3








          3







          • Gain of 20 is too quiet

          • Gain of 200 is too distorted and can't turn it down to get quiet.


          Choose Gain =50 with 1.2k in series with cap



          Pots do not have a 60dB dynamic range so they usually gang 2 pots {pre-amp gain & power amp gain} to get 30dB in each.





          Solution



          Ganged Pot



          schematic





          But as Dave say's that needs to be an audio log pot.



          enter image description here






          share|improve this answer















          • Gain of 20 is too quiet

          • Gain of 200 is too distorted and can't turn it down to get quiet.


          Choose Gain =50 with 1.2k in series with cap



          Pots do not have a 60dB dynamic range so they usually gang 2 pots {pre-amp gain & power amp gain} to get 30dB in each.





          Solution



          Ganged Pot



          schematic





          But as Dave say's that needs to be an audio log pot.



          enter image description here







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 2 days ago

























          answered 2 days ago









          Sunnyskyguy EE75Sunnyskyguy EE75

          63.1k22194




          63.1k22194












          • You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
            – Sunnyskyguy EE75
            2 days ago












          • Isn't this very impractical to adjust volume using 2 potentiometers?
            – ensonic
            2 days ago






          • 1




            They make stereo ganged pots which you can gang to 4 but like said in integrated receivers they gang preamp gain with power amp gain or something better like digital pots. (not for newbies)
            – Sunnyskyguy EE75
            2 days ago




















          • You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
            – Sunnyskyguy EE75
            2 days ago












          • Isn't this very impractical to adjust volume using 2 potentiometers?
            – ensonic
            2 days ago






          • 1




            They make stereo ganged pots which you can gang to 4 but like said in integrated receivers they gang preamp gain with power amp gain or something better like digital pots. (not for newbies)
            – Sunnyskyguy EE75
            2 days ago


















          You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
          – Sunnyskyguy EE75
          2 days ago






          You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
          – Sunnyskyguy EE75
          2 days ago














          Isn't this very impractical to adjust volume using 2 potentiometers?
          – ensonic
          2 days ago




          Isn't this very impractical to adjust volume using 2 potentiometers?
          – ensonic
          2 days ago




          1




          1




          They make stereo ganged pots which you can gang to 4 but like said in integrated receivers they gang preamp gain with power amp gain or something better like digital pots. (not for newbies)
          – Sunnyskyguy EE75
          2 days ago






          They make stereo ganged pots which you can gang to 4 but like said in integrated receivers they gang preamp gain with power amp gain or something better like digital pots. (not for newbies)
          – Sunnyskyguy EE75
          2 days ago




















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