Has anybody build this passive led vu meter? I have been "inactive" in electronics for a while now, I need to fix or build something....I was considering to build this "passive" led vu meter, But again I will have to check if this circuit will affect the impedance seen by the amp at high volume. Six-LED Bar Power Indicator - RED - Page102
It adds a half-wave rectified load to the amplifier. This won't harm the amplifier, but unless the amp has quite a low output impedance it will add a little distortion to the sound. OK for uncritical PA use, but not for serious audio.
Why not just use an LM3915...
http://docs-europe.electrocomponents.com/webdocs/06e8/0900766b806e8b6c.pdf
http://docs-europe.electrocomponents.com/webdocs/06e8/0900766b806e8b6c.pdf
Thank you DF96 for checking it out for me!.
Thanks KatieandDad for link. I have seen it before with "extras" like a 25k and 10K trimmer for the input (pin 5) I guess that is to adjust gain in the input. and some with and without cap from pin 1, I think is to prevent oscillation when leds are placed too far away from IC. What I do not like is some sources have lower outputs than others and I will have to adjust the gain input with trimmer when using a source with a low or high output. I will use it with a passive integrated amp.
amp's specifications:
130watts RMS 8ohms
250watts RMS 4ohms
THD : 0.008% (20 Hz : 20 kHz, 8 ohms)
Frequency Response 4 Hz - 100 kHz
Damping Factor (20-20K Hz, 8 ohms) : 500
Signal to Noise Ratio : 120 dB 'A' weighted
Input Impedance/Sensitivity : 33K / 1V
Thanks KatieandDad for link. I have seen it before with "extras" like a 25k and 10K trimmer for the input (pin 5) I guess that is to adjust gain in the input. and some with and without cap from pin 1, I think is to prevent oscillation when leds are placed too far away from IC. What I do not like is some sources have lower outputs than others and I will have to adjust the gain input with trimmer when using a source with a low or high output. I will use it with a passive integrated amp.
amp's specifications:
130watts RMS 8ohms
250watts RMS 4ohms
THD : 0.008% (20 Hz : 20 kHz, 8 ohms)
Frequency Response 4 Hz - 100 kHz
Damping Factor (20-20K Hz, 8 ohms) : 500
Signal to Noise Ratio : 120 dB 'A' weighted
Input Impedance/Sensitivity : 33K / 1V
Trouble with a passive (led or meter) is you'll need it far far louder then you might think to get any LED's to light. Just rig up one LED/resistor/rectifier to see how it behaves.
Good to know Mooly! I just need the BZX79C2V7 2.7V 500mW Zener Diode to build at least the 2 watts range and see if it will be loud at that range to my taste. The problem is I can not find that Zener diode at Radio shack and I can not order from Mouser just one diode to test this circuit.
It looks to me like the zeners' function is only to clamp the voltage across the LEDs. You could try ~3 1N400x diodes as substitute.
Thanks sofaspud, I will get something to play this week lol. I was checking and I found some nice Stereo led VU meter with transistors, can it outperform the ones using one ic like LM3915?
Why are you going to have to adjust the gain of a VU meter with different inputs? It is showing the output of the amplifier. If you want one to show the input level then just build one with its own op-amp amplifier to show the input level.
I'm confused here. Do you want the meter just to show min to max regardless of the signal level or do you want it to show the signal or output level ??
I'm confused here. Do you want the meter just to show min to max regardless of the signal level or do you want it to show the signal or output level ??
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If you're satisfied with the 3dB/step of the LM3915 I don't see a good reason not to use it.
I have seen a a lot of led vu meters using the LM3915 but, with some "extra" parts. some with a 10k resistor plus a 50K trimmer and some with just a 10K trimmer. other with one cap, two caps and no caps!. I have to get into this a little be more. I saw this one, but it is used to "visual rain" with sensor etc.http://www.instructables.com/id/Visual-rain-sensor/step4/LM3915-VU-meter/
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Mooly...you were right!!! I build the circuit and I had to crank it up too high to light the diodes. I do not think I like the passive way at all. I guess I will have to look for a circuit using LM3915/16.
PS: Very good call Mooly 😉
Here is a trick.
In my audio shop I wind up with stereo receivers and tape decks and other things that have LED VU meters. When I get a receiver or something that is not going to be repaired, I often strip them down to the last screw just as some mindless fun. But I save anything useful like screws or power cords. And VU meters.
In many cases the LED VU assembly is self contained, and usually has four wires:
V+, ground, left signal, right signal.
Easy enough to power on the bench and throw signal at it and watch it work.
If you have an old dead stereo receiver or tape deck with such a VU, maybe you could salvage that.
Your preamp probably puts out a volt or thereabouts. Your speaker signal level is considerably higher than that. YOu can tap into your signal chain anywhere you likie, you just need to adjust the signal level as it enters the meter. That is what trimmers are for.
In my audio shop I wind up with stereo receivers and tape decks and other things that have LED VU meters. When I get a receiver or something that is not going to be repaired, I often strip them down to the last screw just as some mindless fun. But I save anything useful like screws or power cords. And VU meters.
In many cases the LED VU assembly is self contained, and usually has four wires:
V+, ground, left signal, right signal.
Easy enough to power on the bench and throw signal at it and watch it work.
If you have an old dead stereo receiver or tape deck with such a VU, maybe you could salvage that.
Your preamp probably puts out a volt or thereabouts. Your speaker signal level is considerably higher than that. YOu can tap into your signal chain anywhere you likie, you just need to adjust the signal level as it enters the meter. That is what trimmers are for.
Try this one....
BG02 Assembly Kit for Bargraph Display suitable for LM3914 & LM3915 | eBay
Or from closer to where you live.
http://www.ebay.com/sch/i.html?_trk...3.TR0.TRC0&_nkw=LM3915+kit&_sacat=0&_from=R40
BG02 Assembly Kit for Bargraph Display suitable for LM3914 & LM3915 | eBay
Or from closer to where you live.
http://www.ebay.com/sch/i.html?_trk...3.TR0.TRC0&_nkw=LM3915+kit&_sacat=0&_from=R40
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This circuit is a bit smarter: the first LED will begin to glow with an input voltage as low as 1V, ie 0.125W.
Not quite what you can achieve with an external supply, but way better than the circuit you picked:
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