Introduction: Retro Analog Audio VU Meter From Scratch!
I always wanted to have an analog VU meter. I wanted to buy it, but I couldn't find one that was cool enough(and still reasonably priced) so I made my own.
Here I am going to shown you how I created this very cool looking stereo analog VU meter and I will also give you all the needed information and data so you could build your own!
(better functional demonstration video in the last step)
I made this VU meter and video almost 3 years ago (you can see that my newer youtube videos are much more refined now :) )
But now I decided to revive the project to honour the Instructables 1000th contest! I made a new PCB revision (the old one had some problems) and the VU meter is now finally Instructable-worthy!
It plugs in standard 3.5mm headphone jack or a Line Output and it also has a pass through jack, so if you plug it into your mp3 player or phone, you can plug it in the back end and you plug you headphones for listening in the front.
It has an adjustable gain, so you can set the sensitivity no matter the volume you are listening to. It is not really a true VU Meter in terms of an instrument (to show you when the signal is clipping), but it is rather just a cool gadget to rock on your desk. :)
It also has an adjustable backlight brightness, so it is visible no matter what is the ambient light intensity.
And it is be powered from 5V mini USB plug.
Enough said, watch the short video presentation above to see its features in action :)
Step 1: Skills and Tools
This is an intermediate level electronics projects.
You should have at least some experience with soldering PCBs, reading schematics and working with electronic circuits.
As the tools go, you need a soldering iron with a fine tip and some basic tools like wire clippers. You also need a 3D printer if you want 3D printed enclosure. But you can also make your own from wood or plastic. It could come out much cooler.
But if you are less tech savvy and do not know how to solder PCBs but you still want to make an analog VU meter, then you should consider something like this:
AMAZON LINK: https://amzn.to/3vmxP2i
Or you can get only the dials: https://bit.ly/38ri5kO
I also ordered this item half a year ago, I wanted to make enclosure for this version as well for Instructables, but I still didn't receive the parcel... Maybe someday the postman will surprise me.. :)
Step 2: Finding Analog VU Dials
It is difficult to find nice looking VU dials. I salvaged some from a broken Akai cassette player.
Go on a local junkyard or try to find some cassette players on garage sales. These old VU meters from old equipment can be very cool and retro looking.
Or you can try to look for some on ebay. You should find the some that suit you. Just search for analog VU meter.
Pretty much all of them are the 500uA of current type, which is the type that is supported with this electronics.
Step 3: Schematics and Assembly
I found the base schematic somewhere on the internet and I tailored it to suit my needs. I added the dimmable backlight and adjustable gain. See the full schematic in the .pdf attached.
I will not go into depth on how this circuit works, but in principle, it detects the amplitude of peaks in the audio signal and it converts it into current that drives the analog VU dials.
Some short notes on the schematic:
J1 and J5 are connectors for connecting audio wires from your device via 3.5mm audio jack connectors (or the ones you will use). They are wired in parallel, you you can use on for input and the other one for output (pass-through). So if you want to connect it to mp3 player, you can still plug you headphones in for listening. AUDIO_N is ground (the last ring on the 3.5mm connector), the other two are right and left channels respectively.
J6 and J7 are used to connect a dual gang potentiometer for audio gain.It should be logarithmic(audio). I used the ridiculously expensive P9A2R100FISX1103ML (Farnell order number 8791384). Ideally you would use reverse log audio potentiometer, since the normal one works backwards. When you turn it clockwise, it decreases the sensitivity. But I can live with that since I couldn't find a reverse log potentiometer at that time.
R11 and R32 are small PCB multi-turn trimmers which are used to calibrate the channels so both meters show the same gain level at given volume - to fine tune.
J2 and J3 are where you connect the VU meters. P is positive and N is negative lead.
J4 is where you connect a 5k - 10k logarithmic potentiometer which is mounted at the back and you use it for dimming the LEDs
The D11 PESD5V0L4UG protection diode is used to prevent static electricity zapping your circuit when you insert the connectors. Circuit works without them without problems.
Step 4: PCB
Here I have the gerbers if you want to manufacture your PCB:
I use JLCPCB for manufacturing the boards. The cost of this board is only 2$ for 5pcs (plus shipping) which is a bargain! Sign up to get $18 new user coupons: https://jlcpcb.com/IAT
You can use coupon code "JLCPCBcom" at checkout for a small discount.
I used a bunch of JST PH connectors on the board. But you can omit them
if you don't have the crimping tools for them and you can solder some wires directly to the holes. It is much easier and effective.
I also attached the assembly instructions and Bill of Materials in the .pdf. Attached there are files for the newer design, I created just for this Instructable. Initial design had some problems but this one works well.
Step 5: 3D Printed Enclosure
Here is the design for the enclosure. If you have different dials, you will need to modify it, if you need Inventor or .step files let me know in the comments.
Step 6: Final Assembly
Install all the connectors and potentiometers in the box and turn it on and hope there is no smoke coming out :)
Go to some online tone generator page and set a constant tone of low volume. Adjust the controls and see if they work properly. With the fine tune trimmers, adjust the circuit, so both left and right channels have the same deviation.
The main gain knob should work reversely - if you rotate it clockwise, the sensitivity will decrease. Unless you find the reverse log potentiometer, this is how it will work. I find it cool, because you always have the knob turned as much as the volume knob on the device is turned.
Add some knobs on the potentiometers and some rubber feet underneath.
The front knob controls the gain - so you can set the maximum needle movement at any listening volume. The rear potentiometer controls the LED backlight brightness.
Step 7: Enjoy Your Magnificent Creation!
I am sure you will want to spend hours looking at those dancing dials :) They have something magical inside them, especially if YOU are the one who brought them to life :)
I hope you enjoyed my Instructable!
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