Bring Audio Into Your Computer: Build An Audio Breakout Box

Updated on August 21, 2019
Doc Snow profile image

Doc Snow is a life-long musician who loves to record his own compositions. Here's how to bring audio into your computer inexpensively.

Completed project.
Completed project.

Introduction

Recently, I was forced to replace my trusty MacBook Pro, and opted for a newer iMac. It was a great choice in many respects, but raised a problem. One of the core applications for me was audio recording--and one thing the old MacBook had that the iMac does not was an audio input jack. So, how was I to get my audio to the iMac?

One solution is to use an audio USB adapter. Many interface boxes provide just this functionality, but standalone units are also available for a few dollars online. Although I have not used such a product, online reviews seem in general to be positive, and this would likely be a successful choice for most users.

However, there is an alternative. I said above that the iMac does not have an input jack, but that isn’t quite true. Strictly speaking, one should say that it doesn’t have a separate input jack. There is an audio input; it’s just that it’s combined into one jack with the output.

Apple accomplishes this by the use of what’s called a ‘TRRS jack.’ TRSS stands for Tip, Ring, Ring, Sleeve. These terms denote the 4 separate sections of the TRRS plug’s shaft, visible in the photo below. Each of those sections conducts either a single channel of audio, or provides a ground (return path).

TRS vs. TRRS plugs

TRS (top); TRRS (bottom)
TRS (top); TRRS (bottom)

The sections’ assignments are shown in the table below.

TRRS section assignments

Tip
Output audio, left channel
Ring 1
Output audio, right channel
Ring 2
Ground
Sleeve
Input audio, microphone

So you can simultaneously use that TRRS jack to input a channel of audio into your iMac (or similar computer) and to output your stereo mix from it. What you need is an interface box, containing the correct wiring to separate the input audio from the output audio. Luckily, this is not hard to build.

(Note that this means you will be limited to recording mono channels, since there is only one input channel available via the jack. If you want to record in stereo, you’ll need to go the USB adapter route. For me that was not a problem, as I almost never have occasion to record in stereo. On the other hand, this direct audio connection guarantees zero latency due at the hardware level.)

Project requirements: Time, Skill, tools, supplies

I was able to build my breakout box in an afternoon--perhaps about 4 hours, being very careful at every step. You need basic wiring skills--the ability to strip and solder wire, and the ability to read a simple wiring diagram--and tools to match: wire cutter and stripper, probably a small Phillips screwdriver for disassembly purposes, and a soldering iron with solder and desoldering braid (or the equivalent). You’ll also need electrical tape and/or shrink tube to insulate connections. A multimeter will also be extremely useful in checking terminals and solder joints, and a TRS extension cable will be a very handy accessory to it.

For salvage items, I used a game controller and a dead Discman salvaged from the local Goodwill store, and a cheap headphone set from Walmart. The three together cost less than $10.

Items used for salvage

Item bought
Item salvaged from it
Purpose
“Boggle” game controller
2 RCA plugs with cords
Stereo audio input to breakout box
Defunct Sony Discman
Stereo audio output jack
Stereo audio output from box to headphones
Smartphone earbud set
TRRS plug with cords
I/O plug connecting box to Mac
Salvage items (earphones not used for this project.)
Salvage items (earphones not used for this project.)

Item #1 will vary according to the audio outputs you are using or wish to use. I’d been using the RCA “2-channel” output jacks from my mixer and opted to continue using that format. But one could use ¼” instrument jacks or even (balanced) XLR cable.

Similarly, item #2 can also be almost anything with a stereo audio jack, either ¼” or ⅛” (3.5 mm), according to your preference. The Discman turned out to be a slightly unfortunate choice in that the line output jack turned out to be mono, and the headphone jack was physically housed with a jack labelled “remote”. This made for a somewhat clumsy installation, as we shall see.

Item #3 is common; any set of phones or earbuds that includes a microphone will of necessity be in TRRS format.

You’ll also need some sort of case. It could be a commercial ‘project box’. But in the spirit of salvage, I used the plastic cap from a bottle of laundry detergent, glued to a base made from scrap plywood. Supplies for that part of the job were a little black spray enamel and some silicon adhesive.

The steps required to salvage the bits you need will vary according to your ‘finds’. In my case, they can be summarized as shown in the table below.

Salvaging parts

Game controller
Discman
Earbud set
Cut cords free, allowing ample length for your anticipated needs
Remove case
Cut cords free below mic (that is, leave the earbuds and mic connected as an ‘offcut’)
Strip insulation and tin leads for later soldering
Carefully desolder and remove jack from circuit board
Carefully strip the outer insulation and separate leads
 
 
Burn off insulation from each lead--discussed in detail later--and tin leads for later soldering
Discman circuit board, removed.
Discman circuit board, removed.
Line out jack, desoldered and removed.  (Unfortunately, a mono jack!)
Line out jack, desoldered and removed. (Unfortunately, a mono jack!)

Note that the earbud cords, if they are typical, will have a micro-coating of plastic insulating each wire. These can be removed by burning them off with a flame, such as that from a lighter.

The plastic is pretty volatile, so the process is very fast. Just a second or so will do! The wires are very fine, and relatively fragile.

Once all the salvaged pieces are prepared--including any drilling or cutting needed for your chosen project case--you are ready to start wiring. Getting it right the first time requires care and patience--plus your multimeter and that TRS cable mentioned above.

Before diving into the diagram itself, you should know that the stereo headphone jack will be in TRS format. (There's a TRS jack pictured with the TRRS one above.) As you might by now guess, it’s quite similar to the TRRS format, but with one ring fewer, since it is meant to carry only two audio channels, not three. As shown in the wiring diagram below, the tip and first ring coincide with the TRRS scheme, and the sleeve provides the ground.

Wiring the box

Construction hints

  • Depending on your box, it may be quite important to do as much wiring as you can prior to assembling the components to the box, so that you don’t have to try to manage a hot soldering iron in too small a space. As shown below, the headphone jack in particular may benefit from have leads pre-attached before mounting the jack into the box. Be careful to avoid shorting between terminals; the space is quite tight.


Stereo jack with extension leads.
Stereo jack with extension leads.
  • It’s convenient to start by connecting all your grounds: R2 on the TRRS jack; S on the headphone jack; and the sleeves, S, from the RCA plugs. Check that all connections are solid, using your multimeter.
  • You may have difficulty identifying which terminal on the headphone jack should be soldered to which wire. Simply insert a TRS (headphone) extension cable into the jack. Then you can use your multimeter to determine which pin corresponds with the sleeve on the extension plug.
  • Speaking of the RCA plugs, I opted to tie the wires RCA tips at the last point possible, which is where these wires are soldered to the conductor leading to the sleeve on the TRRS plug. This is essentially a “Y-connector” combining two audio signals into one. Of course, since I only intend to record mono, these will be identical signals which will simply reinforce one another. Use the multimeter to identify the wire connected to the TRRS sleeve, then check your solder connections.
  • Finish wiring by connecting the left channel (headphone jack T to TRRS plug T) and right channel (headphone jack R1 to TRRS plug R1). Once again, the extension cable and multimeter will help you to identify the correct conductors.

Wired and (mostly) assembled.
Wired and (mostly) assembled.
  • Finish any assembly not done prior to wiring. Provide “strain relief”--that is, make sure the wires are secured against pulling. You can use knots, clamps, silicone or electrical tape to physically protect your wiring. You may also be able to use strain relief built into your salvaged plugs, as I was with the RCA jacks, by slotting them tightly into the case and securing with silicone.
  • Paint your project, if desired. My paint job was distinctly 'rough and ready'; yours can be as refined, or wild, as your heart desires!

Comments

    0 of 8192 characters used
    Post Comment
    • Doc Snow profile imageAUTHOR

      Doc Snow 

      2 months ago from Camden, South Carolina

      I've had one or two good experiences with the Geek Squad, Aleena, so it is very gratifying to know that they are such fans of mine...

    • profile image

      Aleena Wilson 

      2 months ago

      This is such an amazing invention. And this is so cheap i can imagine ever, Thanks for sharing this wonderful thoughts. If you are looking for service of Technical issue Then Geek Squad Phone Number have knowledge about the complexities of specialized support and repairs, visit: https://www.xgeeksquad.com/geek-squad-phone-number... get office equipment repair, home repairs, etc. for 24*7 tirelessly.

    • Doc Snow profile imageAUTHOR

      Doc Snow 

      2 months ago from Camden, South Carolina

      Thanks for checking out this Hub! I'd love to hear about your experiences with the project, alternatives to it, or just creative audio/tech in general!

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, turbofuture.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://turbofuture.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)