Do cables really matter? (Part 2)

May 15, 2016 by Fu Yongwei in audio, tech

In this post, I would like to focus on my views in buying high-end premium cables for your audio system. As previously mentioned, cables act as a medium to transmit signals between hardware. Hence, a good quality cable will retain signal integrity for the system.

Premium cables such as the Audioquest Angel 3.5mm to RCA cables are easily priced at around $1000 USD for a 1m cable. As a comparison, a similar type of cable from a generic brand such as Cable Matters would cost around $10 USD. That is a huge sum of money to be invested in a single cable and that calls for a more in-depth review to justify purchasing the high-end version.

Left: Audioquest Angel 3.5mm to RCA cable, Right: Cable Matters 3.5mm to RCA cable

When it comes to evaluating the quality of a certain cable, there are a few aspects we can look at. As mentioned in my previous post, a balanced cable is resistant to unwanted interferences even in long cable distances, as the signal will go through a differentiating process to cancel out the induced noise. Regardless of material superiority, whether the cable is being made of gold or copper, an unbalanced cable (such as the 3.5mm to RCA cable) is susceptible to unwanted interference.

Do take note that if a balanced cable is used in an unbalanced output, the cable will still be carrying an unbalanced signal and vice versa. Using the correct type of cable for the right application is therefore important, as it will cause unnecessary problems if not followed through.

Audio cables are passive, meaning there is no active circuitry built inside to improve signal quality. It is a transmitting medium that carries signal from one point to another, where the signal loss will be a factor that affects signal integrity (in this case signal strength) relative to distance. Unless the cable is using some proprietary transmission protocol, premium cables do not improve any signal quality, as it is basically a passive medium.

In addition, even when only premium cables are used in connecting different audio hardware together (e.g. from DA to speakers), one would have to be mindful that the internal wiring of these audio hardware does not utilise these "premium" cables in its circuitry. Thus, the premium cables have pretty much no influence in terms of signal integrity improvement, as the rest of the hardware does not make use of them. Although you can try and redo all the wiring schematics in your beloved audio gears with premium high-end cables, I am fairly sure that this will not have any significant enhancement towards your system performance.

A twisted pair (balanced) cable is almost as good as it gets when it comes to retaining signal integrity, as the twisted pair conductors improve CMRR and the balanced cable is resistant to interferences. The introduction of a Star-Quad Cable was to further improve the immunity to interferences and it has shown real-world improvement. These four conductors shielded configuration can be thought of as two twisted pairs twisted together. Using four small conductors in place of two conductors allows the loop area of the cable to further reduce and improve rejections towards electromagnetic interference. Star-Quad cables seem to be used mainly in live sound applications where long cable runs are common.

As a bonus, LinusTechTip has also reviewed a $1000 HDMI cable recently and the cable does not show any significant improvements in terms of signal quality.

The Wireworld Platinum Starlight 7 HDMI Cable is probably the best thing we've ever seen come through the office. Just kidding...

Investing in good quality cables is important, as their serviceability will easily justify the cost. I will advise not to spend the unnecessary cash in buying high-end premium cables, as it does not have any influence in your signal quality improvement. I would rather save up the money and invest in another important audio gear such as the power conditioner.

YWFU

Do cables really matter? (Part 1)

May 12, 2016 by Fu Yongwei in audio, tech

It is very common for people to pay little attention to cable quality when building electronic systems. Cables play a huge role in your system potentials, as they are the medium for transmitting data or power. If the cables are inefficient as a transmitting medium, the performance of the system will suffer as there is a high level of signal losses.

Before we continue with this topic, we must first recognise the difference between a wire and a cable. In simplified terms, a wire is a conductor (e.g. copper) whereas a cable is made up of multiple conductors. For instance, a speakon connector cable will usually have a pair of conductors in order to transmit amplified signals to the respective speaker cabinet.

As a result, good quality cables are definitely important when it comes to building a system. In this post, I would like to address a few considerations for any practitioners building an audio system. All audio cables are screened (shielded), meaning that an outer conductor wraps around the others conductors to shield them from electromagnetic interference. The outer conductor may be made of various materials such as wire braid or metal foil.

In most cases, the outer conductor is connected to ground so that any induced currents (due to interference) will flow directly to ground rather than being mixed with the audio signal. However, this is not a perfect solution, which is why balanced signals were introduced.

In an unbalanced cable, there is a single inner core (conductor) that carries the audio signal while the outer screen act as the ground cable. The screen also doubles as the signal return path, hence any interference induced will cause the audio signals to be mixed with the interfering currents. These unwanted interferences are more prominent in long cable distances or where there are nearby sources of strong interference (e.g. dimming circuits).

Even in long distances, balanced cables are resistant against such interferences. As compared to its counterpart, a balanced cable has two inner conductors, commonly known as positive and negative. Similar to an unbalanced cable, the screen conductor is grounded but no signal will run through this path. Balanced audio transmission relies on Common-Mode Rejection Ratio (CMRR) to cancel out any interference picked up in the cable. A differentiating process will be implemented at the input stage of the receiving end to cancel out any noise. If any interference makes it through the screen conductor, it is likely to have the same influence on both the positive and negative conductors, thus the CMRR will reject any interference common in both conductors (positive and negative).

As mentioned, CMRR is based on the premise that unwanted external interference is being induced into both signal conductors equally, but is there any way to minimise the susceptibility of interference pickups to maximise the benefits of CMRR? Decreasing the distance between the two conductors by twisting them together helps to equalise the coupling effect of the interference with the audio signal.

A "loop antenna" is formed when two conductors have a spaced gap between them. Therefore, the farther apart the two conductors are, the large the antenna will be, thus picking up more interference along the line of transmission. Minimising the area between the two conductors helps to reduce unwanted hum and buzz from this type of interference, which the cable shield is almost ineffective against. The distance between the twists is called the lay of a pair. Shortening the lay by increasing the number of twists will improve not only the CMRR but also cable flexibility. Do take note that by shortening the lay distance, it would require more material (wire) and machine time, thus increasing hardware cost.

Understanding the characteristics of a good quality cable is vital in system building, as it determines the signal integrity carried through the medium. As a rule of thumb, if there is no option for a balanced output, I will usually not have any unbalanced cable of more than 5m, any more than that would require a Direct Injection (DI) box to transform the unbalanced audio to balanced. The above characteristics have been proven to help sustain signal integrity in real world practices and investing in a bunch of good quality cables is certainly wise.

YWFU

Investing in your audio system? (Part 3)

April 28, 2016 by Fu Yongwei in tech, audio

One of the most important and often forgotten component in an audio system is a power conditioner. It does not look as fanciful as compared to a vinyl player, but the features it provides will substantially affect your system performance. Buying a power conditioner is similar to buying one-time payment insurance for your audio system. Once you owned one, you do not have to put thought into it again.

As the name applies, a power conditioner "conditions" incoming AC power for your audio system. In engineering terms, it means that it filters and cleans out unwanted noise from the incoming AC circuit. There are many causes of unwanted noise induced into a circuit, for example, machines with a motor such as a fan or a refrigerator. In general, a power conditioner will regulate the incoming voltage and improve the quality of power that will be utilised by your audio system.

Audio hardwares tend to be more sensitive in nature and their performance and quality will be greatly affected by inherent noise from the incoming power supply. To illustrate, have you ever experienced buzzing sounds from your speakers whenever a certain device is turned on, or do you hear any hissing sound coming from your speakers (no music playback) even when the level of your output is really low? This can be caused by AC noise, but it can also be a cause of noise induced from an unbalanced cable (if you are interested to know further, do let me know in the comments).

Many of us take this for granted when we ignore the fact that our residence power circuits have been shared by many appliances of different loading requirement. Chances of your audio system's AC supply being clean are relatively low and will cause unnecessary inconvenience towards your user experience.

Commonly, power conditioners will also include a surge protector feature in order to safeguard your hardware's longevity from unwanted power spikes. Do take note that a surge protector does not provide backup power in case of a power failure (e.g. blackout) as that is a job for an uninterruptible power supply (UPS). However, a surge protector will limit the spike in voltage power so as to prevent any chances of overloading in your audio hardware.

I am using a Furman AC 210A E power conditioner for my Digital Audio Workstation (DAW) due to its small footprint, though it is a little bit pricier as compared to its other counterpart that provides roughly around the same features. I chose the Furman's power conditioner as it provides conditioning and surge protector features in a compact chassis. The fuse can be replaced easily and is widely available for me to purchase in case of a power surge. For this particular model, the power output uses IEC connectors, and you might have to take that into consideration as it is quite difficult to find power strips with incoming IEC connectors. Despite that, fabricating an IEC power strip is relatively easy (if you have some electrical knowledge) as IEC connectors can be bought easily at Sim Lim Tower.

Furman Desktop Power Conditioner (IEC connector), my personal fabricated IEC Power Strip.

A common misconception I often hear is that people often associate power strips that come with surge protector with the ability to "clean up" incoming power. One would have to be mindful that a conditioning filter circuit requires a number of circuit components and chances of all of these dedicated conditioning components being packed into a compact size are quite low. Therefore, do not assume that a generic surge protector power strip will have power conditioning features.

Belkin 6 outlet surge protector power strip, a very common product available at local electronic stores. Good for protecting your hardware from power surges but does not filter unwanted noises.

If you are willing or have already invested an amount of money into your audio system, perhaps you should consider a power conditioner. Not only will it help to optimise your system performance, it also prolongs the longevity of your hardware.

YWFU