# VU Meter with Peak Detection



## benny_profane (Sep 27, 2021)

I really enjoy building utility circuits: signal routers, mixers, patch boxes, etc.—anything that can open up different options without changing fundamental elements or introducing anything new.

Even though their real utility is debatable and there are many other (better) line monitors, analogue needle VU meters have always been interesting to me. The addition of the peak detection circuit makes this more versatile and helps give a quick visual indication of transient spikes to avoid nasty clipping with my headphone amp.

I found a cheap DC meter on ebay and worked from the schematic in Figure 9 here. The SENSITIVITY control is a panel control; CALIBRATION is a trimmer. The meter didn't have a backlight, so I made a small LED daughterboard, filed out some notches, and secured it to the meter housing. It's set it so that the backlight is on when the circuit is active.


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## JamieJ (Sep 28, 2021)

That is cool! Good work!


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## Cucurbitam0schata (Sep 28, 2021)

gorgeous work, there!


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## BuddytheReow (Sep 28, 2021)

Nice job!


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## fig (Sep 28, 2021)

That came out beautifully! Very very nice!


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## Feral Feline (Sep 28, 2021)

Love utility, & VU, & sparkle. Funtastic build!


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## Dan0h (Sep 28, 2021)

You sir are awesome. This is such a great idea.


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## benny_profane (Sep 28, 2021)

Dan0h said:


> You sir are awesome. This is such a great idea.


I’ve got a vero layout I can post if you’re interested in trying it out!


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## Dan0h (Sep 28, 2021)

benny_profane said:


> I’ve got a vero layout I can post if you’re interested in trying it out!


For sure!


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## benny_profane (Sep 28, 2021)

The vero layout is attached. The 1k2 resistor is the CLR for the peak indicator LED and can be adjusted to taste. The 470nF cap determines how long the peak LED stays lit after the peak is detected and can be adjusted (I used a 1uF cap). See the notes for Figure 9 for more information. 

For the standing 1n4148 diode, the anode is connected to TL072 pin 1 and the cathode is connected to TL072 pin 2.


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## EGRENIER (Feb 5, 2022)

I've been thinking of something similar but using this board/LED vu level...









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What I can't figure out is what signal level can it take ?  Would a standard Pickup level signal work ?


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## benny_profane (Feb 5, 2022)

EGRENIER said:


> I've been thinking of something similar but using this board/LED vu level...
> 
> 
> 
> ...


It’s not apparent to me that it has an integrated driver, so you may have to supply that. It should be fine with instrument level—you’d just need to ensure that the driver circuit is constructed appropriately. Reference the site in the first post for more information there. The strip board layout above is adapted from one of those circuits.


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## EGRENIER (Feb 5, 2022)

benny_profane said:


> It’s not apparent to me that it has an integrated driver, so you may have to supply that. It should be fine with instrument level—you’d just need to ensure that the driver circuit is constructed appropriately. Reference the site in the first post for more information there. The strip board layout above is adapted from one of those circuits.


Yeah it's really hard to tell... However the board runs in 2 different modes, one is AGC mode which stands for Automatic Gain Control.  So if it can do automatic gain, wouldn't that be an indicator that it does ?

From the technical data I found:

It has dB mode(-40~16dB , for signal monitor) and AGC mode(super wide of AGC adaptive algorithm for better effect).


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