What do these color coding means on the connectors?

When you look at an RCA or RGB connector, there are a variety of color codings on them. For each color there is a corresponding audio or video signal or format. In the back of all consumer electronics products there are matching color codings. This enables the consumer or professional who is doing the installation to use the color codings and greatly simplify the hook up.

An RCA jack, also called a phono jack, it is used for composite video and stereo audio. The name of the connector, RCA, comes from the Radio Corporation of America.

The RCA connector has been adopted for numerous uses other than the original intention, including power connector, RF connector, and loudspeaker cable connector. It is also commonly used for composite video signals, but this application gives very bad impedance matching. RCA connectors may also frequently be used to carry SPDIF-formatted digital audio, with these plugs orange colored to distinguish them from any other typical connections.

The standard colors for the different signals will be described below. There is a color for 13 different signals. These colors are white, red, green, blue, gray, brown, tan, purple, orange, and yellow. The colors green, blue, and red are repeated once, because these three colors have a place in analog audio and in component video.

The first category for color coding we discuss is analog audio codings on the connector. There are color codings for up to eight different audio connections. For the left connection the coding is the color white. The right analog audio connection has a red color coding. Green is the color coding on the connector for the center audio connection. Left surround audio connections are coded by the color blue. The right surround audio connection is colored gray. There are also two colors that are used to color code surround sound audio connections. The color brown is for the connection that goes to the left back surround audio connection. Tan is the color used for coding the right back surround connection for analog audio. The last color coding for analog audio is the color purple, or sometimes brown, and this color identifies the connector for the sub-woofer.

The next category for the color codes that should be discussed is the digital audio connector. This is the orange colored coaxial cable, and carries S/PDIF instead of analog audio. Composite video is another category, and composite video has a color on the connector that is yellow.

Component video is the last color category that will be covered. RGB stands for red, green, and blue. This term applies to various analog components. These components generally offer the greatest analog video signals that are available in consumer electronics. With RGB there is no limit in resolution or color depth, and no compression is used. RGB has been pretty much ignored, despite the suitability and quality, as it can't be easily applied with Digital Rights Management. In North America RGB was never popular for consumer electronics, as the format S-video was considered adequate.

Other types of component analogue video signals do not use the red, green, blue components, but rather a component that has no color, called luma, in combination with one or components that carry color, called chroma, that give only information on color. Both S-Video component video output (which uses two separate signals) and Y'PbPr component video output (which uses three separate signals) that are seen on DVD players are a good example. By converting video into signals called luma and chroma, this conversion allows for a process called chroma subsampling, a method which JPG images and DVD players use to reduce most storage requirements for video and images.

When component video is talked about today, the Y'PbPr component video scheme is usually what is meant. Many consumer products use this format of color coding, such as DVD players, video projectors, plasma displays, and others. In component video there are three components that have a color coding. The first component is Y, and the color it is coded to is green. Component Pb is associated with the color blue on the color coding. The component Pr has a color coding association that is red.

And we hope that you be able to hook up easily at any given time. Good luck.

Bi-amplification of Loudspeakers

Many audio enthusiasts see bi-amping as an intelligent upgrade for their hi-fi systems. Bi-amping is, simply, the process of "doubling up" on amplifiers in a system and hence doubling available power. This article seeks to point out some important considerations to bear in mind when bi-amping speakers.

Don't Mix & Match
It is crucial when bi-amping speakers that you not mix and match amplifiers. One current trend among audiophiles is to use a solid state amplifier for the bass frequencies, and a tube amplifier for the mids and highs. While this may initially seem logical, there are several reasons why this is a bad idea. Let's take a look at each one independently...

Rise Time
For one thing, two different amplifier designs will inevitably have different rise time specifications (sometimes referred to as event time). For the purposes of this discussion, we will define rise time as the time required for a signal to travel through an amplifier. Depending upon the amplifier circuit, the rise time will vary. Even a small mismatch in rise time will significantly degrade the sound of a bi-amped system.





Consider that in a bi-amped system, there are two possible configurations. The first, pictured above left, is more common. In this scenario, one stereo amplifier is dedicated to the high frequencies, and one amplifier to the low frequencies. The other scenario, pictured above right, is referred to as vertical bi-amping. In this scenario, one stereo amplifier is used to run both the high and low frequencies on one loudspeaker. (Note: In each of these scenarios, obviously two monoblocks could be used in place of one stereo amplifier).

In the case of "standard" bi-amping, any discrepancy in rise times would result in timing mismatches between the low and high frequencies. This sort of mismatch between frequency ranges will degrade the sound substantially because the precision in timing is important to maintain the integrity of harmonics. When a hammer strikes a string on a piano, it is not one frequency which is reproduced, but several - the fundamental and each of its harmonics. In a loudspeaker, it is likely that the fundamental will be reproduced by one driver, and the harmonics by at least one other driver. Hence any timing errors will result in a degradation of tonal balance, and a smearing of the soundstage.

In the case of "vertical" bi-amping, discrepancies in rise times will result in mismatches between the left and right channels. The results will obviously effect imaging, especially soundstage depth. A simple analogy clarifies the scenario: using amps with the same rise time is important when vertically bi-amping for the same reason using cables of the same length is important.

Gain
Another critical consideration is the gain of each amplifier used in a bi-amped system. The greater the gain of an amplifier, the more quickly the amplifier's output will increase as the preamplifier's volume control is augmented. Conversely, as the preamplifier's volume is attenuated, the amplifier's output will decrease at a rate directly proportional to its gain. One simple way to think of the net effect of an amplifier's gain is to associate high gain with bigger "steps" in volume and lower gain with "smaller" steps in volume.

What this means in the case of "standard" bi-amping, is that if the gain of the amplifiers is not matched, the volume of the highs and lows will be changing at a different rate as the volume on the preamplifier is adjusted. In the case of vertical bi-amping, the volume of the left and right speakers will change at a different rate. The effects of these volume discrepancies should be fairly obvious: in the first scenario tonal balance is altered, and in the second scenario the stereo channel balance is altered.

Concluding Remarks
Bi-amping provides many benefits, especially when using lower powered tube amplifiers where the system's overall power output can be doubled easily by simply bi-amping the loudspeakers. Many of our customers at Symphony Sound bi-amp with SET tube amps (2A3's, 300B's, etc.) and enjoy wonderful sound as a result. However, it is important to bear in mind that if certain guidelines are not followed, bi-amping can actually do more harm than good. If careful attention is paid to gain and rise time, it is possible to mix and match amplifiers, but only is unusual circumstances do we feel this is a sensible and prudent approach.

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Rhodium Properties

ON RHODIUM

Rhodium is an element with atomic number 45 and the chemical sign Rh. The name comes from the Greek "Rhodon" which means rose.

Rhodium, which is a platinum metal, is the rarest metal on earth (apart from the radioactive metals) and is only a few (less than 10) tons a year are produced. The metal is silvery white and has a higher melting point and lower density than platinum. Rhodium has low electrical resistance, low and stable contact resistance and high resistance against corrosion.

Rhodium is mainly used in alloys with platinum and palladium. Rhodium can only be plated on nickel, silver, gold or platinum. Plated rhodium is extremely hard wearing. Rhodium is sometimes used in spark plugs for aircraft engines, the tip of fountain pens, telephone relays and in the reflectors of headlamps, mirrors and optical instruments. Rhodium is also used in jewellery, as decorations and as a catalyst.

Because of its low and stable contact resistance and its high resistance against corrosion and wear (for example contact surfaces grinding against each other) it is eminently suitable as material in different kinds of connectors. A surface plated with gold, which is a very soft metal, is worn off much faster than a surface plated with a hard metal like Rhodium.

Summing up: Gold is beautiful, but if you want the best (in sound as well) use Rhodium.

MORE:
Atomic number: 45
Atomic symbol: Rh
Atomic weight: 102,9055
Electron config: [Kr]5s14d8
Atomic radius: 134,5 pm
Melting point: 1964 °C
Boiling point: 3695 °C
Oxidation states: 3

SOURCES
Rhodium occurs natively with other platinum metals in river sands of the Urals and in North and South America. It is also found with other platinum metals in the copper-nickel sulfide area of the Sudbury, Ontario (Canada) region. Although the quantity occurring there is very small, the large tonnages of nickel processed make the recovery commercially feasible. The annual world production of rhodium is only 7 or 8 tons.

PROPERTIES
The metal is silvery white and at red heat slowly changes in air to the resquioxide. At higher temperatures it converts back to the element. Rhodium has a higher melting point and lower density than platinum. It is highly reflective, hard and durable.

USES
Rhodium's primary use is as an alloying agent to harden platinum and palladium. Such alloys are used for furnace windings, thermocouple elements, bushings for glass fiber production, electrodes for aircraft spark plugs, and laboratory crucibles. It is useful as an electrical contact material as it has a low electrica resistance, a low and stable contact resistance, and is highly resistant to corrosion. Plated rhodium, produced by electroplating or evaporation, is exceptionally hard and is used for optical instruments. Rhodium is also used for jewelry, for decoration, and as a catalyst.

HANDLING
Exposure to rhodium (metal fume and dust, as Rh) should not exceed 1 mg/m3 (8-hour time-weighted average, 40-hour week).

COST
Rhodium costs about $ 1.000/troy oz.

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1/4" Stereo, Balanced or Insert?



There's a lot of confusion surrounding 1/4" connectors, especially the kind with 3 contacts.

An example of a 3 contact 1/4" plug, Switchcraft part number 297, is shown above. This part is also called a 1/4" TRS connector, where TRS stands for tip, ring, and sleeve, referring to each of the 3 contact surfaces on the connector. While this type of connector is often called a "stereo" connector it is important to understand that the stereo configuration is not the only way the 1/4" TRS connector is used.

Following are the 3 most common signal configurations for this connector:

• The first is as a stereo connection, most often used with headphones. In this application the tip connection is used for the left *unbalanced positive signal. The ring is used for the right signal. The sleeve is the ground connection for both the right and left. This type of connection is commonly found on high end consumer audio equipment and on professional mixing consoles and recording equipment.
• The second common use for the 1/4" TRS connector is as a *balanced audio connector. In this case the tip connection is used for the "hot" connection, the ring is the "cold" connection, and the sleeve is connected to the cable shield. The balanced 1/4" connection is often used as a line level output on professional audio equipment.
• The third use is as an insert connection, often found on mixing consoles. In this application the tip is used as the send, or output signal from the mixer channel. The ring is used as the return, or input signal to the mixer. On some mixer models the tip and ring are reversed. The sleeve is used as the ground connection for both signals. In this application the signal path in the mixer is broken when the 1/4" plug is connected to the insert jack causing the signal path to flow through the equipment attached to the insert cable. An insert cable would normally have the 1/4" TRS connector on one end and split out to two seperate connectors to attach to the input and output of the outboard equipment.

So, what is the important lesson here?

Don't assume that just because the cable fits the interconnection will work. It is in many cases possible to connect one of the types listed above to one of the other types with an adapter cable. Look closely at equipment manuals to find out exactly how the inputs and outputs are wired. If the two pieces of equipment don't have the same connection type you may need an adapter cable or additional equipment to make your connection.

*Balanced vs. Unbalanced signals - The complete explanation of balanced audio wiring is too big a topic for this post, so I will be doing a complete post on this subject in the near future. Suffice it to say that balanced wiring is a way of reducing external interference in an audio line that requires 2 signal wires twisted together, and in the case of most audio installations surrounded by a braided or foil shield. For a balanced cable to be effective both the signal source equipment and receiving equipment must have balanced connections.
An unbalanced line relies solely on the shield for protection from interference and only requires 1 signal line plus the shield conductor which also acts as the signal ground.

Subwoofer Cables, Fact or Fiction?



A common myth/misconception propagated by the hi-fi audio cable industry is that a special, usually larger and heavier, audio cable is required to connect a powered subwoofer to an audio system. In truth, any good quality audio cable that can be used for interconnecting audio components will be excellent for use as a powered sub cable.

The input of the powered sub is a high impedance type which means only a tiny amount of power is transferred through the cable, the power amplification occurs inside the subwoofer at its internal power amp. Because there is so little power transferred through the cable, its conductor size is insignificant. Typically 22, 24, or even 26 gage conductors are appropriate, and will not have noticeable signal loss even at lengths well over 100 ft.

The signal most commonly used by a powered subwoofer is a limited bandwidth line level audio signal. In this case limited bandwidth means that high frequency information is removed from the signal either at the a/v receiver - preamp/processor, the subwoofers input circuitry, or in some cases both. Capacitance is the primary factor in high frequency loss in audio cables. Since high frequencies are not used by the subwoofer the capacitance of the subwoofer cable is not as important a specification as it would be for interconnecting full range components.

So, don't be fooled by high priced "subwoofer" cables, use a normal audio interconnect and your sub will sound just as good.

Can you make a component video to RGB cable?



On an almost daily basis we receive requests for a cable to convert component video to RGB or the opposite. I'd love to be able to build one of these, and would probably sell quite a few of them. However, there are a few technical issues in the way.

Before I get into the details of what we can and can't do I think it would be helpful to define some of the relevant video standards and terms:
• Component Video - Also known as Y/Pb/Pr, Y/Cb/Cr, YUV, and EIA/CEA-770.

The component video standard calls for three parallel channels on 75 ohm impedance coaxial cables. Component video cables are typically terminated with RCA connectors for consumer applications or BNC connectors for professional applications. The three channels are known as Y (luminance) essentially a black and white representation of the image, Pb (blue color difference) , and Pr (red color difference). All three of these signals are derived from different combinations of the red, green, and blue primary colors present in the image.

The component standard describes several different signal formats which differ in resolution and scanning method (interlaced or progressive). The standard explicity defines the formats as 480i and 480p in both 4:3 and 16:9 aspect ratios - called standard definition, and 720p and 1080i - called high definition. The number indicates the visible horizontal lines of resolution in the image, the letter indicates progressive or interlaced scan. Additional formats are also present on some equipment.

• RGB Video
RGB uses 3, 4, or 5 parallel channels to seperately carry the red, green, and blue primary color signals and timing information. The 4th and 5th channels are used for different implementations of the timing (sync) signal. The 3 channel version has sync combined with the green signal and is also know as sync on green. The 4 channel version has the horizontal and vertical sync pulses combined on a seperate line, this version is known as RGBS or RGB composite sync. The 5 channel version has the horizontal and vertical sync pulses on two seperate lines, this version is called RGBHV or RGB with seperate sync. RGB cables are made with 75 ohm coaxial cables and usually have BNC connectors though RCA connector are occasionally used.

• VGA
VGA and its relatives SVGA, XGA, and UXGA are very similar to RGBHV. This standard is used in computer displays and some projection systems. In addition to the seperate Red, Green, Blue, Hsync, and Vsync signals present in RGBHV the VGA family also have some additional lines for digital data communications between the display and computer. VGA cables have 5 coax lines and a varying number of twisted pairs and single conductors for digital data. The standard VGA connector is a 15 pin high density d sub (hd15).

So, how do you convert from RGB to Component or Component to RGB?
Simple enough, all you have to do is combine the RGB signals according to a specific formula to derive each of the component video signals. For example Y = .299R + .587G + .114B. The Pr and Pb signals are derived with similar equations. The reverse conversion is also accomplished with a similar set of equations starting with the Y,Pb, and Pr values. Also, the horizontal and vertical timing signals (sync) have to be processed and combined with the appropriate channel.

While it looks simple on paper it is too complex to be achieved with a simple cable, fortunately there is a type of device called a transcoder designed to do this sort of conversion. Transcoders vary in price from approximately $250 to $1500 depending on signal quality and features. Many scalers combine transcoding with more advanced switching and format/resolution conversion.

How about RGBHV to VGA?

Good news, this can usually be done with a simple adapter cable with 5 BNC or RCA connectors on one end and a HD15 connector on the other. For this to work the devices on both ends must be set up for the same resolution and format. This cable is just adapting, not converting.

How about Component to VGA?

Many video projectors and plasma displays accept a component signal on an HD15 connector, in this case you can use a simple 3 RCA to HD15 cable to make the connection. It's critical to make sure the display is specifically equipped to accept component on this input since the cable isn't converting component to VGA, it is just adapting the connection for the HD15 input.

Conclusion-

The wide variety of signal formats and standards can make integrating a system challenging. Fortunately it is possible to make the necessary conversions with minimal or no loss of signal quality using the appropriate adapters, cables, and transcoders.

Till next time....

Conclusion -

Using the guidlines presented in this paper to select the proper type of audio cable for a project will optimize system performance and in most cases reduce the overall cabling expense. The chart below lists some common audio cable applications and expamples of recommended product types.

Example Application Chart

Application: Speaker

Permanent Install:
SSC-122SSA105 12 AWG stranded BC twisted pair and PVC jacket

Portable:
Gepco GSC132 13AWG stranded BC twisted pair and TPE all weather jacket

Patching:
Gepco GSC122OFC 12AWG stranded OFC BC w/ transparent PVC jacket

Application: Instrument

Permanent Install:
N/A

Portable:
Gepco GLC20 20AWG stranded TC w/ 95% BC braid and semi-conductive PVC tape and flexible matte PVC jacket

Patching:
Gepco GLC20 20AWG stranded TC w/ 95% BC braid and semi-conductive PVC tape and flexible matte PVC jacket

Application: Mic/Line

Permanent Install:
Gepco 61801EZ 22AWG stranded TC twisted pair w/ 100% foil shield and PVC jacket

Portable:
Gepco M1042 20AWG stranded TC w/ 95% TC braid and TPE all weather jacket

Patching:
Gepco XB401 24AWG stranded OFC BC w/ 95% TC braid and flexible matte PVC jacket

Application: Digital Audio S/PDIF

Permanent Install:
Gepco VPM2000 20AWG Solid BC w/ 95% TC braid and 100% foil Shield and PVC jacket

Portable:
Gepco VE61859M 22AWG stranded BC w/ 95% BC braid and flexible matte PVC jacket

Patching:
Gepco VE61859M 22AWG stranded BC w/ 95% BC braid and flexible matte PVC jacket

Application: Digital Audio AES/EBU

Permanent Install:
Gepco 5596EZ 24AWG Stranded OFC BC w/ 100% foil shield and PVC jacket

Portable:
Gepco 5596M 24AWG Stranded OFC BC w/ 95% OFC BC braid and flexible matte PVC jacket

Patching:
Gepco 5596M 24AWG Stranded OFC BC w/ 95% OFC BC braid and flexible matte PVC jacket

Definitions

Wire : metal in the form of a usually very flexible thread or slender rod

Cable : an assembly of electrical conductors insulated from each other but laid up together usually by being twisted around a central core.

Conductor : a material or object that permits an electric current to flow easily

Insulator : a material that is a poor conductor (as of electricity or heat)

Current : a flow of electric charge; also: the rate of such flow

Inductance : a : a property of an electric circuit by which an electromotive force is induced in it by a variation of current either in the circuit itself or in a neighboring circuit b: the measure of this property that is equal to the ratio of the induced electromotive force to the rate of change of the inducing current

Capacitance : a : the property of an electric nonconductor that permits the storage of energy as a result of the separation of charge that occurs when opposite surfaces of the nonconductor are maintained at a difference of potential b: the measure of this property that is equal to the ratio of the charge on either surface to the potential difference between the surfaces.

Balanced Line : a : an audio transmission line where the signal is applied differentially between two conductors, each of which has equal impedances to ground or common.

Impedance : a : the apparent opposition in an electrical circuit to the flow of an alternating current that is analogous to the actual electrical resistance to a direct current and that is the ratio of effective electromotive force to the effective current

That's all for the moment, folks. Thank for reading & visiting. Would like to wish "Gong Xi Fatt Choy" for those who celebrate Chinese New Year & Prosperity year ahead.

The Fins