Need audio input indicator

graygem · 11th April 2011, 08:58 PM

I need an circuit for a simple audio input signal indicator for a small 3 channel mixer. I just want to be able to know when I have a audio signal coming into the channel.

zdavesf · 11th April 2011, 09:04 PM

look up a comparitor circuit. Can be done with with cheap (or expensive) opamps. but comparitors like LM393 are best. you can also get the LM3915 chips and have a VU meter.

Dave

graygem · 12th April 2011, 04:34 AM

I'm looking for something simple with a low parts count. Could you direct me to anything specific?

AndrewT · 12th April 2011, 10:56 AM

lm391x LED drivers
strip of rectangular LEDS, or discrete LEDs.

Did you try looking up lm3915 after that previous posting?
What's the point of asking if you are not prepared to listen?

graygem · 12th April 2011, 01:44 PM

The point is I need something cheap, and simple. The lm3915 is too much for what I want, it is also an obsolete chip. All I want to do is know when an audio signal is present on a mixer channel. One single LED. Something like this peak indicator circuit.

from Extreme Circuits that I just found.

LAJ · 02:32 PM

Thats about as cheap and simple as it gets.
But I like the Samsung chip KA2281. It has hysteresis that the LM39xx chips do not have.
It only drives 5 LEDs which makes it simpler to build.

graygem · 12th April 2011, 05:24 PM

I also found this.
Audio LED.jpg

Will this run alright on 12v? Or what should I do to run it on 12v?
Thanks.

LAJ · 12th April 2011, 05:50 PM

Surely the transistors will operate at 12V. The pot will probably have to be re-adjusted and/or changed to a higher value.
The advantage of hysteresis in an audio display is that at low passages the LM39xx LEDs will flicker.
Whereas, with hysteresis, the LEDs are either full on or full off. Some people like this display better and professional equipment often uses this technique.

digits · 12th April 2011, 06:17 PM

How about 3 DPDT relays, with an LED parallel with the coils, rotary switch to switch from relay to relay.

Itsmee · 12th April 2011, 08:21 PM

Quote:

Originally Posted by graygem

I also found this.
Attachment 218181

Will this run alright on 12v? Or what should I do to run it on 12v?
Thanks.

Change the 100R to 1K.

The simplest you could make it is this.

11th April 2011, 08:58 PM	#1
graygem diyAudio Member Join Date: Jul 2010	Need audio input indicator I need an circuit for a simple audio input signal indicator for a small 3 channel mixer. I just want to be able to know when I have a audio signal coming into the channel. __________________ Professional Newbie.

11th April 2011, 09:04 PM	#2
zdavesf diyAudio Member Join Date: Apr 2006 Location: alberta canada	look up a comparitor circuit. Can be done with with cheap (or expensive) opamps. but comparitors like LM393 are best. you can also get the LM3915 chips and have a VU meter. Dave __________________ we all have to start somewhere...

12th April 2011, 04:34 AM	#3
graygem diyAudio Member Join Date: Jul 2010	I'm looking for something simple with a low parts count. Could you direct me to anything specific? __________________ Professional Newbie.

12th April 2011, 01:44 PM	#5
graygem diyAudio Member Join Date: Jul 2010	The point is I need something cheap, and simple. The lm3915 is too much for what I want, it is also an obsolete chip. All I want to do is know when an audio signal is present on a mixer channel. One single LED. Something like this peak indicator circuit. from Extreme Circuits that I just found. __________________ Professional Newbie.

12th April 2011, 02:30 PM	#6
LAJ diyAudio Member Join Date: Mar 2008 Location: Atlanta Ga. USA	You meant LM339 Thats about as cheap and simple as it gets. But I like the Samsung chip KA2281. It has hysteresis that the LM39xx chips do not have. It only drives 5 LEDs which makes it simpler to build. Last edited by LAJ; 12th April 2011 at 02:32 PM. Reason: Added info


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12th April 2011, 10:56 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	lm391x LED drivers strip of rectangular LEDS, or discrete LEDs. Did you try looking up lm3915 after that previous posting? What's the point of asking if you are not prepared to listen?

12th April 2011, 05:24 PM	#7
graygem diyAudio Member Join Date: Jul 2010	I also found this. Audio LED.jpg Will this run alright on 12v? Or what should I do to run it on 12v? Thanks. __________________ Professional Newbie.

12th April 2011, 05:50 PM	#8
LAJ diyAudio Member Join Date: Mar 2008 Location: Atlanta Ga. USA	Surely the transistors will operate at 12V. The pot will probably have to be re-adjusted and/or changed to a higher value. The advantage of hysteresis in an audio display is that at low passages the LM39xx LEDs will flicker. Whereas, with hysteresis, the LEDs are either full on or full off. Some people like this display better and professional equipment often uses this technique.

12th April 2011, 06:17 PM	#9
digits diyAudio Member Join Date: Apr 2011	How about 3 DPDT relays, with an LED parallel with the coils, rotary switch to switch from relay to relay.

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