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Old 28th September 2008 , 01:02 AM
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Occasionally you need a cable which is just not available "off the shelf", and there's nothing for it but make your own. With a bit of practice with the soldering iron, it's no problem. Here's an example - I was recently asked how to connect an "Aux" output from a PA desk to the mic/line connector of a laptop. The Aux output is on a 1/4" TRS "balanced" jack, and the input on the computer is on a 3.5mm stereo jack. Using a standard lead with a size adapter does not work in this situation - the "tip" and "ring" on the aux connector are "phase" and "out of phase" signals, but on the laptop they are "left" and "right" signals. What's needed is a lead which connects the "ring" on the aux connector to ground, and connects it's "tip" to both the "tip" and "ring" on the laptop 3.5mm jack.

The easiest way to do this is to adapt an "off the shelf" 3.5mm jack to "twin phono" lead - these can be bought in Maplins etc., and are often used for connecting iPods etc. into hi-fi equipment.

Two of these leads are shown in the photo below. (I've used a light coloured one, and a black one, so that at least one of them should be clear in the photos).



We will not be touching the 3.5mm end - these are horrible things to solder up, so by using a lead where this end can be retained, life will be easier.
The first step is to remove the phono plugs - snip them off, and at this stage, put on the strain relief collar for the 1/4" jack plug. (You could do it later, but it's really annoying when you get the soldering completed, to realise you forgot!) Step one is shown below:-



Next, strip the ends of the two wires - take care not to cut right through the insulation and cut the fine copper conductors. This generally takes a bit of practice! On the black cable below, you can see the two halves of the figure-8 (or "zipper") cable stripped individually. On the light coloured cable, you can see the next step - both shields, and both centre conductors (red and white in this cable) have been twisted together ready to solder.



Before attempting to solder wires to a connector, both parts should be "tinned" - this means applying a coat of solder to them, without making a joint. There's a very good reason for this - if you don't, the much greater mass of the connector, compared to the lightweight wire, will draw away all of the heat. The solder will melt on it, and adhere to it well, however the wire may not reach a high enough temperature, and the solder will just flow around it rather than fusing to it. This will result in a bad connection - a "dry joint". Below are two 1/4" connectors - the one on the left is just out of the packet, the one on the right has been tinned.



Now "tin" the wires and trim them to length. First solder the screen connection to the connector body as shown on the left below, then solder the centre-wires to the tip connection on the jack plug.

Now "tin" the wires and trim them to length. First solder the screen connection to the connector body as shown on the left below, then solder the centre-wires to the tip connection on the jack plug.



There are a couple of points to note from the photo below. First notice the slight bend in the wires - this is deliberate. The entire assembley will be held quite rigidly by the strain relief chuck and collar once you assemble the connector, but if the cable happens to get a tug, you want the strain relief to take up the force - not the actual solder joints, which is where the wire is weakest. The slight bends in the wires help in this. Second, look carefully at the two strain relief chuck parts in the picture - notice that one is slightly longer than the other. The one on the right has had a part broken off. This is because the length of the strain relief chuck determines how many twists of the collar are needed to tighten up the assembley. On a big cable, having the chuck assembley too long makes it almost impossible to get the collar screwed on (therefore the small extension piece is broken off). On a small cable, if too many turns are needed, the chuck may not fully tighten on the cable (so leaving the extension on makes it tighten after fewer turns). That's maybe not too well explained - best thing to do is leave the chuck assembley intact unless it's really hard to get the strain relief collar fitted.



Almost there - the next photo shows the strain relief chuck clipped on over the cables, ready for final asembley.



You may find that in order to get the body of the jack plug over the rest of the assembley, you need to hold the chuck part onto the wire as shown below:-



Now simply slide the body over the main assembley, and tighten the strain relief collar onto it. As you tighten it, it closes the jaws of the chuck, which hold the wire in place. Job done....



As well as being used as an output cable to get signal from a desk etc. into a laptop, this cable can be used for inputing signal to the desk - for example, playing back from a laptop into a single mono line level input on a desk or PA amp, or for playing back from a laptop (or iPod etc.) via a DI box.
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Last edited by ndk; 28th September 2008 at 10:43 AM. . Reason: posts merged. <
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Old 28th September 2008 , 01:42 AM
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Stagesound you naughty minx you have really out done yourself now!!! I have tried soldering a jack together and just ended up with a pile of spent solder and burnt fingers, really great post
Ban the 4 pic limit nudge nudge ndk
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Old 28th September 2008 , 10:46 AM
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I have upped the maximum images per post to 12 (which includes any images you may have in your sig).

I have also merged Stagesound's 3 posts into one.
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Old 28th September 2008 , 01:08 PM
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Great post stagesound


It may be of interest to people how I have my studio wired.

The basic components are as follows:

Mixer - balanced ins (24) and outs (16)
Signal processing - mostly balanced ins/outs at pro line level (+4dBu), but have a korg kaoss pad v3 with is unbalanced comsumer level (-10dBu).
Synths - these are a mix of balanced in and outs and unbalanced ins and outs.
Patch bays - all balanced connections, with the 3 patch bays divides as follows:
- 1 for mixer inputs - 24 channels from the mains outs of various synths, guitar processors etc - these are all use in normal mode
- 1 as access points for the various signals processor and effects
- 1 as access points for additional ins and outs of various synths

The goal for me was to ensure that all audio signals are balanced compatible at the patchbays regardless of whether the device connected to the back is a balanced or unbalanced on its input or output.

For devices that are balanced ins or outs, these is easy - simply connect with a suitable balanced lead. (A general point, I *never* run mics and therefor phatom power thorugh the patch bays - this even includes mic inputs that are capable of generating phantom power even if its allways switched off).

For devices that have unbalanced ins and outs then I ended up making two types of custom cables as follows:

For unbalanced out to balanced input - ie typical of a synth output connector to the mixer via the patch bay, then I have them wired as follows:

T (+signal) -> T (+signal)
S (shield) -> R (-signal)
S (shield) -> S (shield)

The thinking behind this is to aim to have any electrically induced noise equally present on both +signal and -signal such that it gets cancelled out by the balanced differential input. Of course such a lead doesnt do anything to help with the lower resulting line level of an an unbalanced signal.

For balanced out to unbalanced input, then I simply leave the -signal disconnected of the source end, so:

T (+signal) -> T (+signal)
R (-signal) - not connected
S (shield) -> S (shield)


For connectors, I allways use neutrik (as pictured in stagesound's post above) - they are well made, easy to assemble and have good cable strain relief for both their 1/4" jack and XLR connectors.

For cable - I have ended up using van damme mic cable (it was what maplin had in stock...), purchased on a 100m drum - so far gone though 3 drums of it wiring this place up. Its seems to be good quality soft sleeve cable (similar to the lynx pro range of cables) ideal for fixed studio wiring or connecting to a stage snake. It isnt solid enough for cross stage use where it may get tramped on etc. You want a cable with a much harder wearing and more solid sleave.

Soldering iron - I stringly recommend a temperature controlled iron - I bought mine from maplin and one with good power behind it. The problem with soldering is its allways a fine balance between the time it takes to melt the solder and how much heat passes up the conductors you are soldering.

Electrical coductors tend to make good heat conductors as well (if you have ever paid much attensions to the heat sink in your computer, you might notice various copper rods or pipes - copper is an excelent conductor of heat).

The problem is if you are using a soldering iron of insufficient power then by the time you have raised the temperature of the solder to make it melt, alot of that heat may pass up the cable or connector and start melting nearby plastic, potentially leading to future shorts.

So I generally have my iron set to around 330C and a stubby tip with about 1mm cross section at the end. Ie enough to even quickly re-melt the solder on the ground connection of a TRS connector (as shown in stagesound's post)..

Cheap soldering irons with long thin tips are near useless for thise kind of work as they simply cant transfer heat into the solder fast enough to raise the temperature of solder on a ground sleeve before the heat has passed through into the rest of the connector and started to melt plastic parts etc.

Also I tend to avoid cheaper gas powered irons - many of them actually provide way too much heat energy for this kind of work. They are great for jewelry and metal working however

Other essential tools:
- solder sucker - one of those spring plunger things is good
- wire cutters
- wire stripper suitable for stripping outer sleave, or actually a small sharp knife can be better for this
- wire stripper suitable for stripping the inner wires - the type I use is one of those that grips the wires and has has a cutting blade that comes down to cut and strip the sleeve when you squeeze its trigger.
- Hobby grib - basically a little stand with various clamps or croc clips for holder what you are soldering.
- multi-meter / connectivity+short tester, or that behringer cable tester
- pactice at soldering properly to ensure good connections without melting any nearby plastic

I have never actually looked for connectors and cable at DV, if they dont have either, then other suppliers I have used are Maplic Electronics, RS Components and Farnell Electronics.

As for resulting cable quality of DIY cables - well, if you taike care when assembling, particularly watching out for stray strands of wire, poor joints, avoid melting plastic etc, then your cables with be at least as good as any commerically made cables, if not better. I have never had to fix or respace any cable I have made myself - most have been in place for several years and have gone though several iterations of rewiring etc. I wish I could say the same for all commerical cables I have bought.


I used to be an electronics engineer so have several years of soldering day in day out behind me, so making up a cable for me takes only a few minutes, but it doesnt take long to learn to solder properly even if you have never used an iron before.
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Last edited by Khazul; 28th September 2008 at 01:12 PM. . <
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Old 28th September 2008 , 10:24 PM
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Great advice khazul - I too "swear by" van damme cable - I've used thousands of meters of their stuff, and never had a problem with it. BTW, I think you're talking about their install cable - they also do an excellent stage microphone cable - I've got a ton of these made up for me by Van Damme - if you order enough they heatshrink on your name for you. (Great at the end of an evening when your gear is mixed up with other peoples, ans someone's trying to make off with your mic. cables in their trunk!)

The small tipped soldering irons as you say are only for work on PCB's etc., and selecting the correct tip is important. This is becoming more important as lead/tin solder is being done away with, and most of the replacements have higher melting points. (Though I'm surprised you need to go as high as 330 degrees). A powerful temperature controlled iron is the way to go - it will be good for both small components and bigger "heat sinks"!

Although as you say, the cheap gas irons are garbage, some of the more expensive ones are very handy and work well. The big bonus is if you're soldering in an awkward position, you don't have the cable trailing in your way! Also, gas irons tend to be better for very heavy components. The tips however have a very short life, because the catalyst in them seems to last no time!
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Old 28th September 2008 , 10:35 PM
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The reason for 330 is I find 300 isnt quite enough to very rapidly overcome the heat-sink effect of trying to re-melt the solder on the ground of a neutrik TRS connector with the tip that I prefer to use.

So using 330 means you have to work fast, but the advantage is getting loads of heat in before the heat spreads elsewhere - and as you say - it helps with newer lead free solders.


BTW - just looking at you photos - careful about getting lumps of solder on the outside of the ground tabs - can interfer with re-assembly of the connector housing.
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Old 29th September 2008 , 10:11 AM
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Quote:
Originally Posted by Khazul View Post
- careful about getting lumps of solder on the outside of the ground tabs - can interfer with re-assembly of the connector housing.
That's not a lump of solder - that's an "advanced outer sleeve tightening feature"

Of course you're right - there was a bit on the outside, which I wiped off with the iron before assembley, but I really should have done it before taking the pics! Sometimes it's easier to apply the heat on the outside, so that you can set the tinned wire into the pool of solder on the inside (usually when working with heavier cables), but as you rightly point out, and solder on the outside needs wiped off, otherwise the connector will be a tight fit in the sleeve.
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Old 29th September 2008 , 12:43 PM
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handy post stagesound, coincided nicely with me moving house and finding out that hardly any of my cables reach what I need them to in the new studio room. Might add some cable diy to the other diy im already up to my eyes in

thanks
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