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Wiring DIN Connectors

Interconnect


With XLRs or jacks, we normally use one plug per channel; that's a pair of plugs for a normal stereo connection, whilst with phono plugs there's no option, because they're inherently a single circuit connector. DINs are multipole connectors however: a single 5 pin DIN plug may involve one or even two stereo terminations. If, for the sake of avoiding serious crosstalk, we elect to use a single-core screened cable for each channel, this means squeezing 4 wires into the cramped DIN plug interior, which is nearly impossible, save for using stingy, ultra-thin cable. So we recommend that whenever possible, you stick to a single stereo connection per DIN plug, typically either an input or an output.

In instances where you must have access to all four connections via one cable and plug, the most sensible plan is to use 4 core cable with a single overall screen. This will exhibit considerable crosstalk, so keep it as short as possible - under 12" if possible.

Single cables will terminate neatly with jack, phono or XLR connectors at the other end, but not a 4 core, as there's no overall screen, and certainly no protective sheathing for each core as it splits out to travel to its respective jack/phono/XLR. You can get around this by making a termination box. Figure 1 shows a diecast box, inside which the 4 core DIN cable is terminated. The signal then splits out to four XLR chassis sockets mounted in the box. You can then use your standard XLR cables (say) to link up thereafter. For 'XLR', you can of course read jack or phono, whichever refers to the standard interconnection in your studio. You may, by the way, find this termination box concept helpful -in solving other interconnection hassles.

Termination Box for DINs


Wiring Layout


Back to the job at hand: in this series of photos, we've used a pair of single core cables. These will need to be no greater than 3.5mm OD (Outside Diameter) to fit through the neck of the bushing. Suitable types include foil-screened varieties from Belden or West Penn, but for best results, the wires inside the sheath should be flexible copper rather than the steel strands used in the above types. Also, single coil foil-screened cable isn't easy to obtain, so you'll end up with the more common, paired cable (2 cores + screen), and this will mean chopping off the extra core in each of the two cables.

In the photos, we have used single core 'medium screened' from RS Components. Although not exactly a high grade cable, it features flexible copper wires (Belden's are springy and hard to twist neatly and tightly) and insulation which doesn't melt too readily. But whichever cable you choose, make sure it's as durable as possible: avoid skinny wires, as they will be continually failing.

Sadly, we couldn't use my favourite single core cable, the single core version of Musiflex, called PHONOFLEX, as it's OD is too great (at 4.6mm) to allow 2 cables to be squeezed into the DIN.

So, with a very limited maximum OD, we can't use low capacitance cables, which naturally tend to be chunkier. Therefore, the pure mechanics of the DIN connector inherently constrain crosstalk performance and top-end response merely by forcing us to adopt thin (small OD) cables. All this underlies the need to avoid using DINs when these parameters are crucial.

Assembly




1) First we cut two equal lengths of single core cable. Next, dismantle the DIN, and slide the body over the two cables. Use a lubricant if this proves awkward.


2) Strip back the outer sheath on each cable about 12", and separate out the screen wires. Do not twist these yet.


3) To avoid the pain of trying to connect the chunky screen wires to the DINs' miniscule ground terminal (pin 2), we make this connection via a short piece of 7/0.2 wire which is bound to the two screens. ('7/0.2' means a wire with 7 strands, each of 0.2mm diameter). This is called a tail. Cut off a 2" length, and strip this back about 1". Then lay out the tail between the two bunches of screen wires, as shown in the photo.


4) Lining up the stripped-back portions accurately, you can now twist the wires tightly together. The photo shows the ready twisted wires being tinned. Put the iron on the wire for 5 to 8 seconds about ¼" from the point where the insulation begins. Only then should you feed in the solder, pushing it against the wire rather than the iron bit. If you do this, it will only melt and flow once the wire has reached the correct temperature for the flux to act effectively. Overall, this means a better joint.

The tinned area need not extend along the whole (1") twisted section; only the first ½" need be soaked in solder. So why did we strip back a whole inch of insulation? Well, it's easier to twist three wires tightly together when there's a fair length to grip. You're welcome to try twisting 3 wires together with a mere 2mm of wire showing beyond the insulation; it's this sort of mess that results in failed cables...


5) Now we cut off the surplus length - leaving a 5mm 'solder stub' wherein the tail joins to the pair of screens. You can then put a Hellerman sleeve (a short section of expandable rubber tubing) over the join, having first folded over the tail so that it comes out in the same direction as the two signal wires. As an alternative to Hellerman sleeves, use a length of 10mm heatshrink tubing - a match or hot soldering iron will make this shrink tightly around the solder stub. Be sure no stray slivers of wire poke out the end. If they do, chop them off.

The process just described is known as 'serving the cable'. The photo shows the newly-served cable, with the wire ends stripped back and twisted ready for tinning. The distance between the wires protruding from the stub and the stripped-back point should be around 10mm. If you use AB automatic wire strippers, you can strip all 3 wires simultaneously.


6) Leaving the stripped insulation near the tail-ends (as illustrated) is helpful for twisting too. Hold and twist the insulation, and pull gently at the same time. As the insulation slides off the end, the minute strands of wire will be twisted tighter than by nimble fingers alone. The very tight radius of twist is important when wiring DINs, as it helps avoid stray whiskers which so readily snag the wire as it enters the DIN's minute solder buckets.

With the wire ends twisted, and the insulation removed, we can tin the wires. Again, apply the iron, and wait for the wire to heat up before applying solder. Because these thin wires heat up quickly, this will take only a couple of seconds. If the plastic insulation melts in the process, either you're taking too long (5 seconds overall should prove adequate), or your iron is far too hot. This is a common fault with cheap irons when confronted with very thin wires, and you may like to consider a temperature-controlled iron - they are not too expensive and even a basic model will all but eliminate the extremes of excessively low and high temperatures which cause so many problems with Antex irons and the like.

Now chop back the tinned section to 2mm overall length, and dress the wire ends (by judicious clipping) so that their cross-section is circular. The idea is to ensure that the tinned and trimmed wire ends will press neatly into the DIN solder buckets.

Preparation of these comes next. Clamp the insert (the lump of easily-melted plastic in which the DIN pins/terminals are embedded) with lever wrench grips or similar, and hold the iron against the side of each terminal in turn. The bucket will take about 5 seconds to heat up. With the iron still in place, aim thin (22 or 24 swg) solder vertically down the centre of the bucket. If you use the more common and thicker 18swg solder, or come in from the wrong angle, most of the solder tends to end up on the outside of the bucket (the terminal, if you prefer), and will probably short on adjacent pins or melt and mix with the plastic. Feed in only a trace of solder. If, as is likely, the bucket's opening is subsequently clogged up by solder, use a desoldering gun or some braid to remove the excess. Alternatively, flush out by heating the solder, then quickly inverting and very sharply rapping the insert. Too much heat spells melted plastic, and hence it's best to check for this before continuing, as the damage can be easily corrected by reheating and straightening.


7) The reward for all this detailed and precise preparation is that the eventual business of soldering the leads to the DIN terminals is made easier. You should now be able to push the tinned wire ends into the buckets by gripping the wires with your long-nosed pliers - or even tweezers. The photo shows how two of the wires stay in position without being held just prior to soldering. The third wire has sprung out of its bucket, but we can push it back in again for soldering once the other two leads are connected, and the main cable straightened out.


8) This picture shows the last pin being soldered. Did you remember to double check that you're wiring up the right pins - now was it 1 and 5... or 3 and 5?

Heat the bucket for about 4 seconds. You may now add a very SMALL amount of solder to the iron to aid heat conduction. Once heated, apply thin (22swg) solder to the top of the bucket from above, feeding in only a small quantity, and ensuring the lead Wiring Layout is pushed firmly into the bucket. This completes the wiring.

Note 1: Good wiremen keep a reel of 22swg solder handy for fiddly jobs like this one. If you don't want to buy a whole reel, your local pro-audio dealer may be willing to supply a length - say 6 metres. This is a relatively short length, as thin solder is 'eaten up' quickly.

Note 2: In the photo, the solder is seen being applied from one side so you can see the work layout. This is INCORRECT. It should be aimed into the bucket, from above.


9) Now you can begin to reassemble the DIN. With the usual RS type, the cable clamp clips into the insert. If the solder stub (covered by sleeving) has a rectangular profile, align its narrowest dimension so that it lies across the cable clamp. This will buckle up the wire ends, but of course, it also takes any major strain off them.

With the two cables in position, we grip them by squeezing the clamp around the stub, with long-nosed pliers as seen here in the picture. Note also the vital slack in the 3 wire ends. Try to squeeze the clamp symmetrically, otherwise it will slew over, and it may be impossible to assemble/screw together the plug.


10) In the photo, you can see the wired-up plug before we slide on the cover, and add the latch and the fixing screw, shown below the main assembly. Use Loctite to prevent this screw coming undone, or alternatively, put a sleeve over the connector. If you're into exotica, Canford Audio supply heat-shrink sleeves with your own name, logo or address and phone number; these are built to fit over jack and DIN plugs, and probably help if leads disappearing outright is as much a problem as disintegrating leads. Have you also spotted the Hellerman sleeve just behind the plug's body? A series of these, spaced at intervals, hold the pair of cables together until they split out to their respective XLR/Jack/B Phono plugs, about 9" from the other end.


11) And here's the completed assembly. On the RS DINs, you can write identification fairly indelibly on the rubber bushing, using a spirit-based felt tip pen. If necessary, transparent heatshrink tubing will protect the labelling from wear. Alternatively, it allows you to use self-adhesive labels, which would otherwise fall off after a dose of strong sunlight, or become heavily soiled.

If the lead is for general use, an arbitrary letter and/or number (eg.'R2') is best. For a dedicated purpose, aim to identify the equipment, and the function of the connection, eg. 'DDT' and 'RET' on either side of the bushing. DDT is an abbreviation for an imaginary FX unit, whilst 'RET' indicates a Return. Equally, SND for send, L and R are obvious, CX for control (a footswitch say), PWR for power, LN for line, and so on. Next month, we move on to phono connectors.



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Constructing a 'floating' studio floor

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Realistic PZM


Home & Studio Recording - Copyright: Music Maker Publications (UK), Future Publishing.

 

Home & Studio Recording - Mar 1984

Feature by Ben Duncan

Previous article in this issue:

> Constructing a 'floating' st...

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> Realistic PZM


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