How to make a Mini-RCA Interconnect for your amp - diyAudio
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Old 29th March 2008, 02:17 AM   #1
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Default How to make a Mini-RCA Interconnect for your amp

As per the title, I'm going to explain how to make a mini jack to dual RCA interconnect that could be used to connect your PC soundcard to your headphone amp/DAC/speaker amp. However, I put together this cable BEFORE thinking of doing a FAQ, so I guess I'll try to explain myself as much as possible.

First things first....MATERIALS. You're free to buy anything you want, but I tend to be on the budget side, and still strive for quality. The simplest ICs are made with ready-made cables, like the following:

-Canare L-4E6S Star Quad Micophone Cable
-Mogami W2534 & W2893 Neglex Quad Mic Cable

Mic cables are easy to work with, as they already have 4 conductors, most likely the max. number you're going to use. Also, the aren't too think or thin, and fit into the jacks snugly. BTW, they're also CHEAP. There's also another option with using regular 21-24 AWG stranded wire and braiding them in a Litz configuration, but that's another FAQ.

Talking about jacks, there is a plethora of jacks available. A simple search reveals them all. However, as stated above, I like to be on the budget side, except I also care about quality. Now, you could get jacks that are worth a couple hundred dollars, but it's ultimately up to you. The jacks I frequent are Switchcrafts. They are made right here in Chicago, and are of very high quality. HOWEVER, most retail stores tend to sell them at very high prices, so I suggest going to these online/brick and mortar stores:

-Markertek ($100 min. order for International, BUT can be negotiated)
-Audiogear (they only ship to the US, good prices though)

Next up, TOOLS...You're going to need at least the following:

-Soldering Iron (a Pencil type iron with a pointed/chisel tip is ideal); Stray away from questionable brands, and stick with Hakko, Weller, and other well known brands. NO COLD HEAT IRONS, THEY DON'T WORK!!!!! ***An iron's wattage determines how hot it gets. An iron of 15W to 30W is plenty for fine electrical work like this***
-Solder (logical companion.....); At least 0.20-0.32 dia. 63% tin/37% lead is best (often called 'High Tech solder'). Brands: Kester, WBT, Cardas...
-Iron holder/cleaner; as simple as a curled piece of 8 AWG wire. A damp sponge or kitchen paper is preferable.
-Heatshrink; GET AN ASSORTMENT. There are many types of heatshrink out there, but 2:1 shrink is most common. A 2:1 shrink means that it'll shrink to 1/2 it's original size (3:1; 1/3 shrunk size). Be sure to use the correct size for the job (a piece of heatshrink that is slightly bigger than the material is ideal)
-Wire Strippers
-Side Cutters
-Pliers (to clamp the strain relief)
-Lighters (to shrink the heatshrink...you can also use a heat gun)

Click the image to open in full size.

For more info, go here: Getting Started in Audio DIY

***IMPORTANT: WASH YOU HANDS AFTER YOU'VE WORKED WITH SOLER, I AM NOT LIABLE FOR ANY LEAD POISONING***

Onto the ACTUAL steps...

1) Lay out the cable (I'm going to use Canare Star Quad) in front of you and cut to desired length.

2) Strip the rubber insulation and the metal braided shielding to get to the 4 21 AWG conductors. Neat thing about Star Quad is that the conductors tend to be in two colours only, so it makes life ALOT easier.

Click the image to open in full size.

3) Unravel the twisted wires and designate roles to each of them. I usually use white as my grounds and twist the two wires together. The blues I then designate as left or right channel.

4) Strip all of your wires. You can tin the wires at this point, which makes it easier to work with, but is entirely up to you.

5) Open up your jacks. There should be 3 parts to it: a) A clear plastic tube, B) The metal/plastic shell which covers up the actual connector, and C) The connector itself.

Click the image to open in full size.

Click the image to open in full size.

Up first, the 3.5mm connector. It will have a rod in the middle, and flanges on either side. The biggest flange (with the cable clamp) is usually the ground, which is the part furthest away from the tip of the connector. This is where you solder the two white wires I mentioned earlier to. The rod is the left channel, which corresponds to the tip of the actual 3.5mm jack (ie, before the first black stripe). The other smaller flange is your right channel, which corresponds to the area in between the two black stripes.

Click the image to open in full size.
Simply put, the flange with the hole is ALWAYS RIGHT, and the rod is ALWAYS LEFT

Next, the RCA jack. Since RCA are what we call phono/mono jacks, they only carry on channel of audio per jack. As a result, there is only a rod and a ground. Using the white wire again, it will connect to the flange, which is the ground, and corresponds to the sleeve that slides over a RCA plug. The rod is the left/right channel, and it corresponds to the rod of the RCA jack.

Click the image to open in full size.

6) Construct your y-split. Pick a spot on the Star Quad and cut the insulation & shielding off. Unravel the four wire and retwist them into pairs. REMEMBER, ONE WHITE WIRE WITH ONE BLUE WIRE, NOT BLUE-BLUE AND WHITE-WHITE. Heatshrink the wires afterward.

7) Slide enough heatshrink onto the y-split until it doesn't move or dislodge itself. I also like to slide enough heatshrink onto the wires so that the diameter will be close to the opening of the metal sleeve of the RCA/3.5mm jacks.

Click the image to open in full size.

Click the image to open in full size.

8) Solder your wires to the appropriate parts. NOTE: you don't have to distinguish which blue wire is right/left channel, we'll do that later. REMEMBER TO SLIDE THE BARREL OF THE JACK AND ITS PLASTIC SLEEVE ONTO THE WIRE BEFORE SOLDERING!!!!! Clamp all of the wires onto the barrel with pliers.

I'm not going to teach anyone how to solder, but some hints:
-Heat the part up adjacent to the area you want the solder to be. It flows toward heat.
-Make sure the part is hot enough. If not, then you'll get a cold joint, a joint that is really crappy. A good one should be shiny, NOT dull.

More info + videos here: http://tangentsoft.net/elec/movies/

9) MAKE SURE THE DIFFERENT CHANNELS ARE NOT TOUCHING INSIDE THE CONNECTOR. Just to be sure, I cut a piece of heatshrink and physically blocked off the channels. Screw on the metal sleeve now.

10) To check the different channels, I just grab some alligator clips + wires along with a battery and lightbulb, and construct a simple circuit to see which RCA jack would corresponds to the channel.

11) You're done! Connect to amp and have an eargasm.

Click the image to open in full size.
GREAT SUCCESS!

Brendan
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Old 29th March 2008, 02:30 AM   #2
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Very nice. Well done.

You do know that you can buy these already made...
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Old 29th March 2008, 02:34 AM   #3
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Yep, but it's more satisfying to do it yourself and cheaper.
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Old 29th March 2008, 03:12 AM   #4
TheMG is offline TheMG  Canada
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Well, I dunno about the "cheaper" part. Generic cables can be bought for <$5.

But yes definitely cheaper than Monster cable or other name brand stuff, and on-par in terms of quality (physical quality that is, I'm a non-believer in claims that ridiculously HQ interconnects give better sound).
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Old 29th March 2008, 03:44 AM   #5
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Great tutorial!
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Old 29th March 2008, 03:43 PM   #6
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Oh, and BTW, I found it very helpful to have one of the compress air dusters, as I can turn it upside down and immediately 'freeze' the heatshrink in any position I want. The liquid that comes out is pretty darn cold, as I've gotten burnt by it...
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