Volume control for LM386
$begingroup$
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
edited Jan 9 at 8:06
Peter Mortensen
1,60031422
asked Jan 8 at 19:49
ensonicensonic
13016
$endgroup$
add a comment |
$begingroup$
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
edited Jan 9 at 8:06
Peter Mortensen
1,60031422
asked Jan 8 at 19:49
ensonicensonic
13016
$endgroup$
add a comment |
$begingroup$
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
edited Jan 9 at 8:06
Peter Mortensen
1,60031422
asked Jan 8 at 19:49
ensonicensonic
13016
$endgroup$
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
edited Jan 9 at 8:06
Peter Mortensen
1,60031422
asked Jan 8 at 19:49
ensonicensonic
13016
edited Jan 9 at 8:06
Peter Mortensen
1,60031422
asked Jan 8 at 19:49
ensonicensonic
13016
edited Jan 9 at 8:06
Peter Mortensen
1,60031422
edited Jan 9 at 8:06
Peter Mortensen
1,60031422
edited Jan 9 at 8:06
Peter Mortensen
1,60031422
1,60031422
asked Jan 8 at 19:49
ensonicensonic
13016
asked Jan 8 at 19:49
ensonicensonic
13016
asked Jan 8 at 19:49
ensonicensonic
13016
13016
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
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.
answered Jan 8 at 20:01
Spehro PefhanySpehro Pefhany
212k5162428
$endgroup$
$begingroup$
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?
$endgroup$
– ensonic
Jan 8 at 20:47
add a comment |
$begingroup$
- 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
But as Dave say's that needs to be an audio log pot.
answered Jan 8 at 20:45
Sunnyskyguy EE75Sunnyskyguy EE75
70.1k225101
$endgroup$
$begingroup$
You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 21:18
$begingroup$
Isn't this very impractical to adjust volume using 2 potentiometers?
$endgroup$
– ensonic
Jan 8 at 21:31
1
$begingroup$
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)
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 22:07
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
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.
answered Jan 8 at 20:01
Spehro PefhanySpehro Pefhany
212k5162428
$endgroup$
$begingroup$
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?
$endgroup$
– ensonic
Jan 8 at 20:47
add a comment |
$begingroup$
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.
answered Jan 8 at 20:01
Spehro PefhanySpehro Pefhany
212k5162428
$endgroup$
$begingroup$
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?
$endgroup$
– ensonic
Jan 8 at 20:47
add a comment |
$begingroup$
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.
answered Jan 8 at 20:01
Spehro PefhanySpehro Pefhany
212k5162428
$endgroup$
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.
answered Jan 8 at 20:01
Spehro PefhanySpehro Pefhany
212k5162428
answered Jan 8 at 20:01
Spehro PefhanySpehro Pefhany
212k5162428
answered Jan 8 at 20:01
Spehro PefhanySpehro Pefhany
212k5162428
answered Jan 8 at 20:01
Spehro PefhanySpehro Pefhany
212k5162428
212k5162428
$begingroup$
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?
$endgroup$
– ensonic
Jan 8 at 20:47
add a comment |
$begingroup$
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?
$endgroup$
– ensonic
Jan 8 at 20:47
$begingroup$
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?
$endgroup$
– ensonic
Jan 8 at 20:47
$begingroup$
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?
$endgroup$
– ensonic
Jan 8 at 20:47
add a comment |
$begingroup$
- 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
But as Dave say's that needs to be an audio log pot.
answered Jan 8 at 20:45
Sunnyskyguy EE75Sunnyskyguy EE75
70.1k225101
$endgroup$
$begingroup$
You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 21:18
$begingroup$
Isn't this very impractical to adjust volume using 2 potentiometers?
$endgroup$
– ensonic
Jan 8 at 21:31
1
$begingroup$
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)
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 22:07
add a comment |
$begingroup$
- 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
But as Dave say's that needs to be an audio log pot.
answered Jan 8 at 20:45
Sunnyskyguy EE75Sunnyskyguy EE75
70.1k225101
$endgroup$
$begingroup$
You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 21:18
$begingroup$
Isn't this very impractical to adjust volume using 2 potentiometers?
$endgroup$
– ensonic
Jan 8 at 21:31
1
$begingroup$
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)
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 22:07
add a comment |
$begingroup$
- 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
But as Dave say's that needs to be an audio log pot.
answered Jan 8 at 20:45
Sunnyskyguy EE75Sunnyskyguy EE75
70.1k225101
$endgroup$
- 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
But as Dave say's that needs to be an audio log pot.
answered Jan 8 at 20:45
Sunnyskyguy EE75Sunnyskyguy EE75
70.1k225101
edited Jan 8 at 22:10
answered Jan 8 at 20:45
Sunnyskyguy EE75Sunnyskyguy EE75
70.1k225101
answered Jan 8 at 20:45
Sunnyskyguy EE75Sunnyskyguy EE75
70.1k225101
answered Jan 8 at 20:45
Sunnyskyguy EE75Sunnyskyguy EE75
70.1k225101
70.1k225101
$begingroup$
You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 21:18
$begingroup$
Isn't this very impractical to adjust volume using 2 potentiometers?
$endgroup$
– ensonic
Jan 8 at 21:31
1
$begingroup$
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)
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 22:07
add a comment |
$begingroup$
You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 21:18
$begingroup$
Isn't this very impractical to adjust volume using 2 potentiometers?
$endgroup$
– ensonic
Jan 8 at 21:31
1
$begingroup$
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)
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 22:07
$begingroup$
You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 21:18
$begingroup$
You could get 20log(500/10k)= - 26dB which is not silent that's the approx 30dB limit I said in my answer
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 21:18
$begingroup$
Isn't this very impractical to adjust volume using 2 potentiometers?
$endgroup$
– ensonic
Jan 8 at 21:31
$begingroup$
Isn't this very impractical to adjust volume using 2 potentiometers?
$endgroup$
– ensonic
Jan 8 at 21:31
1
1
$begingroup$
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)
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 22:07
$begingroup$
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)
$endgroup$
– Sunnyskyguy EE75
Jan 8 at 22:07
add a comment |
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