Audio - Balanced split adding LED VU meter Help - Page 1
Forum section: electronics / beginners

author: damonpence
author_rank: Newbie
timestamp: August 26, 2020, 02:04:02 am
content: I need to add LED VU meters to a 56 channel Studio console by spliting the direct outs. The direct out is 50ohms impediance. I need the abitlity to see the Direct output going to the computer DAW interface. I have found some information out there but not sure if it completely applies to my setup. This is a Balanced out from the console, I was adding a dual Fader to allow for input control to the DAW/Meter, spliting the signal at that point to go to the Input of the DAW/Output of the circuit and the other split would goto 1 of the 4 amps in a TL074 so that I can change from a Balanced input to a unbalanced grounded output that I would use to feed my LED VU meter going through a 100k trimmer so that i could calabrate the VU meter.I have created a schematic but I have very.... very.. limited understanding of how to determine the resistor and capacitor values.I am trying/hopeing I can build this without any signal audio quality loss to the output going to the DAW.Any help would be great and very appreciated. I know i am probably asking alot but I would like to have a better understanding on why I would be using certain resistor/capacitor values in my schematic. my schematic is a peice together of things i have found and figured out on my own. right or wrong I am trying to learn.Also, and i can't find where I read it but I it am I suppose to be using a ceremic capacitor or an electrolytic capacitor on both the power + and - input?thanks,DamonVu Meter OpAmp.pdf(10.99 kB - downloaded 116 times.)

author: bob91343
author_rank: Super Contributor
timestamp: August 26, 2020, 03:21:28 am
content: To answer your last question first, the proper way is to use both. The electrolytic capacitor will take care of power line ripple and the ceramic will take care of high frequency.I don't know what DAW means. I don't know what 'splitting' means. If you can't describe what you want, it makes it hard to guess what these things mean to you. 'Going through a 100k trimmer' could mean many things as well.

author: ledtester
author_rank: Super Contributor
timestamp: August 26, 2020, 03:35:10 am
content: Quote from: damonpence on August 26, 2020, 02:04:02 amDo you have a reference for your circuit -- like a circuit you're trying to copy or one that gave you the idea?Your op-amp doesn't have negative feedback so I'm very suspicious of it. It seems you want to use the op-amp in a differential configuration (i.e. as a differential op-amp) -- is that what you're trying to do?

author: ledtester
author_rank: Super Contributor
timestamp: August 26, 2020, 03:41:17 am
content: Also - you might be interested in this ebay listing:https://www.ebay.com/itm/Stereo-XLR-4dBu-To-18dBu-Balanced-VU-Meter-Driver-PCB-Board-Audiophile-Grade/143654188441From the description:Quote

author: damonpence
author_rank: Newbie
timestamp: August 26, 2020, 01:18:29 pm
content: sorry, I should have defined more of what I was needing. To start "DAW" is Digital Audio Workstation, software used for tracking, recording and producing music in a studio environment. That is where the home will be for this build. Having a clean audio signal and no hum or hiss in the audio signal line is very important.Define a few things:Recording Console(Mixer) - Has many channels and I am focusing only on 1 channel, say channel 1. It has Input for microphones and it uses and Op-amp to increase signal, the mixer also has a Direct output that is used to goto your recorder/DAW.Splitting - I need to figure out a way to come out of the board and goto the Recorder/DAW and to the LED VU meter with one audio line coming from the Console.LED VU Meters - These are the meters I am experimenting with, they are stereo but for this circuit I would only want to use one side. Its an unbalanced meter and this is why I am looking at using the TL074.https://www.aliexpress.com/item/33018573177.html?spm=a2g0s.9042311.0.0.675f4c4d8j4ctIWhat i am trying to do:The circuit, I am looking at placing in between the Console's channel 1 direct output and the recorder/DAW. This connection is a simple TRS(tip,ring,sleeve) cable common to the music industry. I want to come out of the Console(directout) and go into both DAW and OP-Amp so that i can keep my balanced signal>then drop that signal down to unbalanced signal> and out to LED VU meter.The circuit i found to use was for a Microphone preamp which I don't think completely applies in my case as I am dealing with Balanced Line signals coming out of the console and if/when a microphone is plugged into the console the internal preamp will take care of any phantom power or amplification needed.Adding Dual pot for output controlhttps://www.gearslutz.com/board/atta...line-fader.jpgPreamp schematic I am working off ofhttps://www.eevblog.com/forum/beginners/tl072-microphone-preamp-(differential)/msg1367512/#msg1367512Quote from: ledtester on August 26, 2020, 03:41:17 amYou are correct it is a Balanced to unbalanced board but it will not work. It is using analog VU meters with drivers and i need this same thing that allows for the use of LED VU meter using audio signal.

author: themadhippy
author_rank: Super Contributor
timestamp: August 26, 2020, 01:29:45 pm
content: what daw are you using as i cant think of one that dosnt have built in metering,and after a few sessions you don't even bother with them as you know xdb on the desk is the optimum recording level for the recording device

author: damonpence
author_rank: Newbie
timestamp: August 26, 2020, 01:43:10 pm
content: Quote from: themadhippy on August 26, 2020, 01:29:45 pmI am using Logic Pro X and StudioOne 5 and you are right, it does have metering but my console is 11ft long and not always easy to see screens. lol, the view I need is never on the right screen. Also, this is a part of a much larger puzzle. once I have this circuit figured out I will have an input meter and a output meter for each of the 56channels.

author: ledtester
author_rank: Super Contributor
timestamp: August 26, 2020, 01:52:53 pm
content: Quote from: damonpence on August 26, 2020, 01:18:29 pmCarefully look at the schematic - you have the + and - inputs to the op-amp reversed.QuoteSomeplace in the circuitry the balanced signal is converted to an unbalanced signal. I would message the seller to see how to tap into this so you can send it off to a LED VU meter circuit. Or ask how to get in touch with "Mercury Magicians" whose logo appears on the board.Update: At the end of this video an email address appears for "Mercury Magicians":https://youtu.be/IyP1PWdXhlY