Hi,
I've just breadboarded the famous Sound Level Indicator from Audioguru (schematic here). This circuit provides automatic gain control.
I have a few questions about it:
1) All is working very well with quiet sounds, but I find it a little less helpful with louder signals (The 6-7 first leds are always on, so only 3 of them are really responding to the sound fluctuations). I'm not sure my circuit is 100% correct, especially in this "auto gain control" part.
When I play very quiet sounds, pin 6 of the 3915 is set to 0.51v, which is correct (I think). But when I play louder sounds, it seems to float around 2v. Shouldn't it be more, something like 5.1v ? That may explain this poor response with bigger signals.
2) As this circuit will be used in a disco (where sounds are probably way bigger than in my living room), I was thinking that it may be safer in my case to adapt the circuit to remove this automatic gain control and add some sensitivity potentiometer instead. How should do that on audioguru's schematic ? Can I simply drop Q3 and R14 and add a pot near R15 ? What value should I try here ? Should I also remove C9 ?
Thanks a lot in advance for helping noobs like me
Nicolas
I've just breadboarded the famous Sound Level Indicator from Audioguru (schematic here). This circuit provides automatic gain control.
I have a few questions about it:
1) All is working very well with quiet sounds, but I find it a little less helpful with louder signals (The 6-7 first leds are always on, so only 3 of them are really responding to the sound fluctuations). I'm not sure my circuit is 100% correct, especially in this "auto gain control" part.
When I play very quiet sounds, pin 6 of the 3915 is set to 0.51v, which is correct (I think). But when I play louder sounds, it seems to float around 2v. Shouldn't it be more, something like 5.1v ? That may explain this poor response with bigger signals.
2) As this circuit will be used in a disco (where sounds are probably way bigger than in my living room), I was thinking that it may be safer in my case to adapt the circuit to remove this automatic gain control and add some sensitivity potentiometer instead. How should do that on audioguru's schematic ? Can I simply drop Q3 and R14 and add a pot near R15 ? What value should I try here ? Should I also remove C9 ?
Thanks a lot in advance for helping noobs like me
Nicolas