Single led vumeter using LM311 comparator at the output amplifier?

[johanx4]

Hi, need a second opinion to review this schematic that a friend gave me. it's supposed to be connected after the preamp audio or even at an high potency output of 100w (speaker terminals). I can connect it after the preamp, but want to go for the easier option that would be if connect it directly to the speaker terminals (friend told me thats safe as well). So its not a problem that way even the amplifier delivering 50 to 100w rms? or should I chance some values? thanks.

 

[Sunnysky]

I already told you in EDA , it won't work.
You need to demodulate the signal with a peak detector and signal conditioner for the. desired response.

 

[(*steve*)]

But surely if you don't like an answer you should keep asking people until you get an answer you like? :-o

 

[duke37]

Why won't it work? If the LM311 is set to give a low output when there is no signal, the fet will be off and there will be no light.
If there is sufficient signal, then the LM311 output will be high for part of the time and the led will be on for part of the time. In other words it is a peak detector. I do not see the need for further conditioning unless you want to stretch the output pulse.

Is this the answer you want?

 

[Sunnysky]

There were two (2) implied questions.
Compatibility and Rhythm response desired.

1) For loading on amp or speAkers distortion , anything> with >1k input impedance will have no perceived effect, perhaps less. For sensitivity, gain/attenuation control is needed from speaker, but not from Line Out if avail (1V typ fixed)

2) using comparator on raw LPF audio signal will result in each positive peak turning ALL LEDs at signal frequency, not rhythm rate like 4 beats per second.

Solutions discussed will not achieve this.

I suggest you confirm your requirements for desired effects have more to do with extract kick drum and symbols that merely clipping Bass with a simple comparator to drive lights dim all the time , e.g. when there are bass signals which may not flash very distinctly on sustained different bass notes.

Bass signals have different notes but necessarily modulated. So LEDs will not flash much.
Detailed design of demod. or "signal conditioning" are needed to match your expectations.

Do understand the difference in sustained bass vs. rhythm sounds?