Episode 19: I'll Take The Gold-free Extra Oxygen Cable Please


Tackling two types of common cables you'll find: Speaker cable and HDMI cables. HDMI they obsess over gold plating; Speaker cable they obsess over OFC. Which is worth the extra money?

Warning: Hardcore audiophiles may be upset by the contents of this episode.

Pre-show Acknowledgements [01:10 - 05:01]

We're always grateful when people take inspiration from the show and write posts or podcast about things we've discussed during the show.

In response to Episode 16 One Man's Hopes and Dreams of an RF Buble Dave Liggat wrote an article called IPv6: An Unreachable Wall that expanded on just how far our the IPv6 'wall' actually is. Thanks to Dave - it was a great read and thanks for doing all the maths for me!

We also really appreciate iTunes reviews and a recent review in the German store from Flavor Dynamics made comment regarding the Outtro music being from a 1980s elevator. Okay, so I laughed when I read that but seriously I've written about The MOD Tracker Scene previously that discusses how I came across that song and the corrections are: it was a 1990s song and is highly unlikely that it was ever played in an elevator. ;)

Oxygen-Free Copper (OFC) [05:02 - 19:06]

OFC cables are typically found in audio applications for stereo systems for connecting the amplifier to the speakers themselves. The configuration of these cables is often referred to as "Figure 8" which is a play on the appearance of the cables cross-section that looks like the number 8. The examples we consider specifically are this OFC Cable and contrasted with a Standard Cable. Making Oxygen-Free Copper perhaps not surprisingly requires an environment with an inert-gas during production that is, well, Oxygen-free.

Technically speaking though it's still valid to count copper as being Oxygen-free even if there are 10ppm or less of Oxygen contained in it. The truth is that OFC copper only presents a 1% improvement in resistance over standard copper and the whist OFC cables are associated with greater reliability this has nothing to do with the OFC nature of the copper but rather the general construction of the cables.

OFC cables use high core counts to acheive the same Cross-Sectional Area (CSA) of equivalent cables and due to Skin Effect this often results in lower effective AC resistance and better performance in that regard only. Claims of improvements to noise performance with OFC over standard copper are unfounded.

Gold Plating Connectors [19:06 - 34:50]

Primary reasons for gold-plating connectors come back to a desire to improve the contact resistance and corrosion-resistance. There's an excellent article called the Golden Rules (PDF) which is from an connector vendor discussing all of the advantages of Gold plating for connectors.

The problem is that all metals will erode with every connection/disconnection cycle of the plug and the socket. How much they degrade (how much is scraped off) will vary based on the hardness of the metal in question. In 1812 a German geologist and mineralogist Friedrich Mohs developed a scale of hardness that is still used today although it has been refined further it at least illustrates the point.

Any plating used will eventually erode as the harder of the two surfaces gouges/scrapes off the other surface with the HDMIstandard for example requiring a 10,000 total connect/disconnect cycles for compliant connectors. Ultimately contact resistance improvements are minimal but measureable but the cost of adding gold to a connector is often over-assumed by consumers. A gold-plated connector of a HDMI cable will have less than 0.1 grams of gold worth less than $5 USD and yet such cables sell for anywhere between $10 USD to $50 USD more than a standard HDMI cable.

Real-world Consumer Applications [34:50 - 45:55]

Ultimately resistance is the enemy with speakers as the more resistance there is between the amplifier and the speaker the less total power is delivered to the speakers. Given a typical household cable run of 10m for a typical 25W bookshelf speaker, comparing the two cables mentioned previously we end up with a total reduction in power output of only 0.3dB of volume. Given that 3dB is half the power output, this is essentially barely measurable by a sound pressure level meter and would be barely noticable by the human ear at normal volume levels.

Regarding HDMI there are both 5V and a I2C(aka IIC) bus on a standard HDMI cable and given the typical length of a HDMI cable is about 5m we can conclude that in order to drop below the minimum "Digital True" voltage a cable of extremely high resistance would need to be used. Looked at another way, given that both gold and non-gold plated cables exist and yet both work, the gold plating does nothing to improve the quality/reliability of the signal transfer for HDMI.

Summary of What Makes a Good Cable [45:55 - 55:42]

Good speaker cables don't need to be flexible or made using OFC in order to perform well. Save the money spent on cables and spend it on a better amplifier and speakers. Good HDMI cables are well shielded. On balance neither gold-plating nor OFC is worth the additional money spent for essentially all consumer applications.

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Episode 16: One Man's Hopes And Dreams Of An RF Bubble

On a marathon episode John critiques the Artemis pCell presentation, critiques a lengthy article about how pCell might work and finally walks through the key pieces to understanding if  this is real life or is this just fantasy; and whether Steve Perlman is the right man to make this dream a reality.

Episode 15: Extend or Recode

When you’re asked to or need to use someone else’s software code in your project it’s not always a clear cut choice how to approach the problem. Do you extend or do you recode?

John and Ben explore the pros and cons and put forward some practices to reduce the potential damage.

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Episode 14: The World's Most Popular Camera

The iPhone has disrupted the consumer photography industry. It is the most popular camera in the world. But is it the best camera? To answer this question, John explores the limitations of using the iPhone as your only camera, the benefits and drawbacks of owning a DSLR, and how accessories like the AtoB iPhone Camera Grip can make a big difference.

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Episode 13: Safety, Safety Everywhere

John and Ben discuss ways to take reasonable but meaningful safety precautions in the workplace, and around the home. 

Episode 12: Pages Blocks Planes Die Bank Device

Episode 2d: The Battery Problem Follow-up 4

John addresses some more follow up from Episode 2: The Battery Problem. The topics are: Flywheels as a form of energy storage, the challenge of disposing of or recycling dead solar panels in 40 years and realistic expectations of DC efficiency.

Thanks for the follow up everyone, keep it coming!

Episode 11: Cause and Effect

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Episode 10: Passion Over Academic Proof

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This episode is a little bit different. To celebrate double digits, we recorded LIVE!, and John actually agreed to go a little bit meta. Ben loves meta.

We're going to keep on recording the show live too, so you should join us. Follow @pragmaticshow on Twitter for announcements. We'll have a show calendar up on the website soon as well. 

Episode 9: The Internet Makes It Even Better

John and Ben discuss the practical risks associated with connecting every single device we own  to the internet. What happens when a piece of hardware has core functionality tied to some remote server and the business model suddenly changes? This subject seemed timely in light of the recent acquistion of Nest Labs by Google. 

Episode 8: A Nice Serene Quiet Environment

John has worked at a lot of places where there are big signs warning of the need for hearing protection. You don't see those signs much in an office environment, but maybe they should be everywhere. 

In this episode John and Ben talk about noise. Noise is a big problem. A lot of people tend to overlook it. A lot of people tend to shrug it off like its no big deal. But you only get one set of ears, and once they're wrecked you're out of luck. 

Special Note: We're running a short poll about units of measurement used in the show as well as the possibility of putting up a live stream when we record. Please let us know what you think!

Show Notes

Partial Episode Transcription


John: The headphones that Apple had before the EarPods I think had been pretty well consistent during that time period. The ones we had up til a couple years ago, those older style Apple earbuds were tested and with different music players, obviously having different power outputs for the headphones, they were suggesting that anything above 50% volume in your headphones were generally something where you should have a time limit for how long you're listening to music. Anything over 50% volume could potentially cause hearing damage over a long enough period of time.

Obviously the louder it is the less time it takes to damage your hearing. To the point at which, if you're at 100% of maximum volume the listening time is down to 5 minutes. So you listen to that at full volume for five minutes and you're going to start damaging your hearing.

Ben: Hmmm. Guess what.

John: I know guess what, right?

What I mean about damaging hearing I'll talk about what I mean in a minute. But just a little more about that. There's been a few independent tests that have been done on the EarPods and if you look at their response and power and what they generate in terms of sound pressure they are simply not as loud compared to the earbuds that they replaced. 

And the reason for that is simple. They've sacrificed containing the audio inside the ear for a bit of comfort. But they've also provided a bit more, ah, how should I put it... the frequency response is more tailored to bass. If you listen to both EarPods and earbuds from Apple as I have and I'm sure many of our listeners have you'll hear that the difference there is quite marked. The low frequency is quite better on the EarPods than the earbuds. 

And that bears out on the tests that I've looked at and are linked to in the show notes. However as a result they do not generate a sum total of as much sound pressure. Essentially what I'm saying is that they're softer. 

Episode 7: A Category Called General