# Building a Mixing Desk



## Diarmuid (Feb 28, 2006)

Has anyone had any experience building a mixing desk? I was thinking about building a Lighting desk, but decided, that was probably not only more dangerous, but probably more complicated (as in the whole DMX protocols...), so when I was talking to my TD today, and he mentioned it was possible, I thought I would try that.

If anyone has got any schematics, from any mixing desks and was able to upload them, that would be absolutley great, and if anyone can give me any views or insights, that would be greatly appreciated.

Thanks in advance

Diarmuid


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## Footer (Feb 28, 2006)

doing a strait level control wouldnt be to hard.... but adding in EQ's.. seperate buses... auxs.... and making it not sound like there is a behive in it would not be an easy feet.... i would sudgest picking up a few good electronics books...


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## fosstech (Feb 28, 2006)

Do yourself a favor and buy an inexpensive mixer if you're concerned about money. I may even go as far as suggesting a Behringer, but if you have a little more money around get a Mackie if you can. You're going to use up too much of your time and money building one yourself and the end result will most likely be less than satisfactory. Building a mixer is a lot more complicated than running the signal through a bunch of pots and soldering the outputs all together. In fact, if you do that, you're going to end up frying whatever is on your inputs. If you're confident with your knowledge of mic preamps, mix amps, EQ circuits, routing, PC board design and construction, and chassis fabrication, than by all means, go ahead. But if you're not, spend a couple hundred bucks on a mixer that will have a warranty, be guaranteed safe, be noise-free, and have technical support behind it.


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## Diarmuid (Feb 28, 2006)

At the moment, my main aim is not as much to get a working mixer out of this, but is more to get a better understanding of the workings of a mixer, so that I get a better understanding, when I do eventually (and hopefully not too far away) buy a half decent mixer. I also thought, that it might be a useful way to improve my electronic skills as well.


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## gafftaper (Feb 28, 2006)

I would say start searching the internet. There are all kinds of crazy things out there. Certainly you will be able to find schematics and design informatino. I bet someone even has a kit you can buy with all the parts to build it yourself. It sounds like a fun project. Be sure to take some pictures and report back on how it went.


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## soundlight (Feb 28, 2006)

I don't know if they still have it, but go to Radio Shack and buy the book "Introduction to Electronics." It will be a full-page size book, with holes punched along the side. Read it. It's got some mixer, preamp, amp, and possibly EQ diagrams.


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## The_Terg (Feb 28, 2006)

Diarmuid said:


> At the moment, my main aim is not as much to get a working mixer out of this, but is more to get a better understanding of the workings of a mixer, so that I get a better understanding, when I do eventually (and hopefully not too far away) buy a half decent mixer. I also thought, that it might be a useful way to improve my electronic skills as well.



If you want a good electronics project that is small, easy to build, and teaches you quite a bit about audio electronics, I would suggest starting with pocket headphone amplifiers.

I built this pocket headphone amplifier as one of my first electronics projects. If you look into the circuitry for that, and if you also compare that to this article on creating active and passive eq circuits, you will find that it gets very complicated very quick. Personally, I aspire to become an electrical engineer but would be satisfied if I could only get the bass boost to work on my gadzooked pocket amplifier. Gotta start small.

After all, the headphone amp is cool and useful on its own. Build the thing into an altoids tin (it WILL fit) and turn some heads. I can't tell you how fun/useful it is to plug my pocketamp into my mp3 player and turn my MDR-7506's into speakers.


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## cutlunch (Mar 1, 2006)

Diarmuid said:


> At the moment, my main aim is not as much to get a working mixer out of this, but is more to get a better understanding of the workings of a mixer, so that I get a better understanding, when I do eventually (and hopefully not too far away) buy a half decent mixer. I also thought, that it might be a useful way to improve my electronic skills as well.



Here is a link that deals with building an audio mixer which looks at each section needed in a mixer.

http://sound.westhost.com/project30.htm

Also check out this page of links to audio circuits

http://www.epanorama.net/links/audiocircuits.html#mixer

Please not that the above link is a subset of links in a very usefull website 
http://www.epanorama.net/

This site has links to anything electronic.

There are sites on lighting, stagecraft, computers, microcontrollers, telephone, audio etc
There are links that newbies can understand up to university thesis level.

I have been going to this site for over 8 years and never been to every link.

It gets updated about every two months.

If I was stranded on a Desert Island and allowed only one Website to access this would be it. (excuse the corny humour) However I strongly believe this website would be useful to over 90% of all Control Booth members. Please note I have no connection with this website except as a fan.

Terg I hope these links help you. Out of interest, electronicaly a DMX512 desk would be easier to make then a audio mixer.


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## mbenonis (Mar 1, 2006)

Diarmuid said:


> Has anyone had any experience building a mixing desk? I was thinking about building a Lighting desk, but decided, that was probably not only more dangerous, but probably more complicated (as in the whole DMX protocols...), so when I was talking to my TD today, and he mentioned it was possible, I thought I would try that.



I know someone who actually built a 16 channel two scene preset DMX lighting console. The catch is he was a fourth-year electrical engineering major at the time. That said, the console works great and is pretty cool looking. If you'd like more information I can ask him for schematics/tips.


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## Diarmuid (Mar 1, 2006)

If you were able to get me any schematics, it would be amazingly great, as one day, after building a mixing desk, I would like to do that, if it would work and would be safe.

Also, does anyone know of any decent electronics shops in the UK, I have tried Radio Shack, but they dont appear to have a UK branch.

Thanks

Diarmuid


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## bdesmond (Mar 2, 2006)

Diarmuid said:


> If you were able to get me any schematics, it would be amazingly great, as one day, after building a mixing desk, I would like to do that, if it would work and would be safe.
> 
> Also, does anyone know of any decent electronics shops in the UK, I have tried Radio Shack, but they dont appear to have a UK branch.
> 
> ...



Rat Shack's not helpful in the US unless your in a bind and need something day-of and are willing to pay. Jameco and Allied are the two catalogs I keep and generally order out of for general electronics supply. I believe they're both available online as well.


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## mbenonis (Mar 2, 2006)

Diarmuid said:


> If you were able to get me any schematics, it would be amazingly great, as one day, after building a mixing desk, I would like to do that, if it would work and would be safe.
> 
> Also, does anyone know of any decent electronics shops in the UK, I have tried Radio Shack, but they dont appear to have a UK branch.
> 
> ...



I'll shoot him an e-mail, although I might not know anything for a week or two - spring break starts tomorrow. It's perfectly safe, as there are no dimmers in the board itself. It simply connects to an existing DMX system (or dimmers that take 0-10V analog control). I've actually played with it and it's really cool.


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## Diarmuid (Mar 2, 2006)

Ok, now I know that these are quite likely to be a stupid questions, but before I go any further there is a couple of things I would like to sort out, and I cant find anyone else to answer them so here goes....

Well basically, I am having difficulty understanding the following diagram, Figure 7 which is about three quarters down this page http://sound.westhost.com/project30a.htm I dont really get how AUX 1, is set up to work pre fade. The little arrow up by the insert, I dont really understand that, is it a join and if it is, why isnt it shown as one? To me it would make sense if that wire, the one stemming from the arrow was to be connected to the wire above it, about where it says R10. Is this what the arrow means,?and also, the eq, and thus the mic, is only connected to the aux 1 pre fade wire, so surely that would mean that unless the wire was joined there, it wouldn't be able to connect to the main fader, and itwould be better to put two wires in, so that one, would take the PFL feed one way, and the other would take the eq (and Mic) the other way, into the top wire.

As in one the wire on the furthest left of the diagram, would contain the EQ signals and the one on the right hand side of that would take the PFL signal, including the EQ'd Mic to the PF for AUX 1. (Those are the two I would put in to replace the one stemming from the arrow.)

Hopefully that will have made sense to somebody, and if you could check the diagram, to see whether it is me or the diagram is messed up, it would be great! 

Cheers

Diarmuid


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## cutlunch (Mar 3, 2006)

Diarmuid said:


> Well basically, I am having difficulty understanding the following diagram, Figure 7 which is about three quarters down this page http://sound.westhost.com/project30a.htm I dont really get how AUX 1, is set up to work pre fade. The little arrow up by the insert, I dont really understand that, is it a join and if it is, why isnt it shown as one? To me it would make sense if that wire, the one stemming from the arrow was to be connected to the wire above it, about where it says R10. Is this what the arrow means,?and also, the eq, and thus the mic, is only connected to the aux 1 pre fade wire, so surely that would mean that unless the wire was joined there, it wouldn't be able to connect to the main fader, and itwould be better to put two wires in, so that one, would take the PFL feed one way, and the other would take the eq (and Mic) the other way, into the top wire.
> 
> As in one the wire on the furthest left of the diagram, would contain the EQ signals and the one on the right hand side of that would take the PFL signal, including the EQ'd Mic to the PF for AUX 1. (Those are the two I would put in to replace the one stemming from the arrow.)
> 
> Diarmuid



It took me a minute or two to work out the circuit diagram you are talking about.

The first thing to remember in his diagrams are that normally the signal enters the subsection you are looking at from the left and leaves at the right. It seems he doesnt use different shaded arrows for input and output. So it took me a minute to work out the flow.

Starting at the left the little arrow on the Channel insert is perfectly normal. It just means that when a jack plug is not put in the socket then the two lines connected by the arrow are joined. This means that the signal coming from the tone section is fed through R10 onto the line where the pre-fade listen signal and the level fader can get the signal.

The arrow is used to show this connection can be broken by the inserting of a jack plug. If a jack plug lead is inserted the audio signal path is from the tone (EQ) section out of the mixer to an effects unit eg compressor etc. This signal is then feed back into the top line off to prefade listen and the fader. Just like it had come straight from the Tone (EQ) section.

Now you can understand the signal path from Tone (EQ) you will be able to see how pre-fade and post-fade work for Aux 1. When you look at SW 1 in it's current position you see can it gets the audio signal from the output of the channel fader op-amp -thus it is post-fade. This means that as you change level of the signal with the channel fader the signal you get at Aux 1 will also change with the change of the channel fader position.

Now if you put SW 1 to the other postion the signal that is found at Aux 1 is the signal from the Tone (EQ) but the channel fader has no effect on the signal level. Only VR3 can effect the level of signal sent at Aux 1.

Aux 2 is wired just as AUX 1 but permanently in the post fade mode.

I hope this helps.


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## Diarmuid (Mar 3, 2006)

Thanks so much. Me and my TD both spent ages staring at that diagram today, and neither one of us could work out what it meant.

Thanks again.

Diarmuid


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## jacobbiljo (Mar 3, 2006)

if your looking for how to build any type of device, whether lighting or sound, 
http://www.commlinx.com.au/schematics.htm has got a lot of schematics and is very helpful. I am completing a lighting board right now using a conglomerate of plans off this site.


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## Diarmuid (Mar 3, 2006)

Ok, I cant work out ANOTHER diagram, well actually, a symbol, which features on every single diagram.... On all the diagrams, there is often a Small down triangle/arrow...what does this mean??? Originally I thought that it was an earth, but in none of my electronics books, does it show that to be the earth symbol, and elsewhere in his drawings, he uses the normal symbol, of the lines pointing down in a triangle. Edit-oops, just realised I didnt put what I was talking about... http://sound.westhost.com/project30a.htm sorry.

(Does it show that I have only just started looking at complex diagrams? [action=Diarmuid]hits self for being an idiot sometimes [/action])

Thanks so much!!

Diarmuid


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## cutlunch (Mar 3, 2006)

I read it as a ground / (earth) symbol.

Cutlunch


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## Diarmuid (Mar 3, 2006)

Thank you very much,

Your help is muchly appreciated.

Diarmuid


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## Diarmuid (Mar 4, 2006)

I'm really sorry for asking loads of what must be stupid questions, but for the resistors on this page http://sound.westhost.com/project30a.htm (with the exception of the peak monitor) as they are all resistors for the signal lines, are they likely to be under 0.5Watts? or will they be running at 48V and thus a much higher wattage I just wondered, because I am trying to find the right resistors.

Thanks Diarmuid


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## cutlunch (Mar 4, 2006)

For this I would be happy using 1/2 watt metal film resistors. (1/4 watts would probably do as well) Get the ones that have 1% tolerance. They shoudn't be to expensive also now they come in the same size as the old 1/4 watt carbon that had a 20% tolerance.

Just for a better quality result I would use multimeter to match the resistors when there are things like voltage dividers etc where the two resistors have the same value. Eg Such as R# and R4 in Fig 4. This will help minimise any offset due to the resistors. EG the 6k8 that feed the phantom power to the microphones.

Just remember that he hasn't shown the power supplies to the IC's so you need to check the specifications. Also make sure you look at his page on the power supply http://sound.westhost.com/project30c.htm

Are you going to make this up using his PCB's ?

Before you get carried away with this project ensure that you can still get the parts or an an equvialent.

Cutlunch


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## Diarmuid (Mar 4, 2006)

Thanks, once again, for saving the day lol!


> For this I would be happy using 1/2 watt metal film resistors. (1/4 watts would probably do as well) Get the ones that have 1% tolerance


I will indeed, (now) use the metal film resistors and test them with my DMM.
As regards to the PCBs, I am planning to use most of the ones available, but as I cant see any for a large part of the product, and dont have the know how or equipment to make any, I am planning to put the rest together on stripboard.

Hopefully, all of the chips and parts will still be available, but I will check as soon as I get out of the tech rehersal tommorow.

Thanks

Diarmuid


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## Diarmuid (Mar 5, 2006)

All the parts are available, at least from various suppliers around the world.

Does anyone, know how capacitors vary in audio circuits, basically does anyone know what frequency, type etc, are needed in audio circuits. Is there a single fixed frequency for all the circuits and are there simply two different types of capacitor needed one polarized, and one not (I realise that those two things do come in a wide range of different capacitors). If they do vary for each circuit, how do I work out what I would need? I am still using the circuits fromhere 
Also, is there a difference between earth and ground, because in the UK, there is but I am not sure where the diagrams in the above link come from, and due to varying symbols, I thought I would check, also, does the earth/ground signal, just go to the earth pin on the plug or does it have to be removed in a different way?

Thanks and sorry for all the questions.

Diarmuid


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## cutlunch (Mar 5, 2006)

The earth /ground we talk about is the power supply ground not the mains ground. If you look at other projects on his web site also look at some of the articles he has written wou will be able to answer most of your own questions. Just use the index link at the bottom of the page.

Just a quick one, the capacitors marked with the + sign are electrolytics and must be put in the right way round. Most come with the negative leg being indicated on the side not the positive.

Cutlunch


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