Anyone that grew up a geek in the late 70’s to early 80’s (ahem) will get the references in this video:
For those of you that are unfamiliar:
The Hitchhiker’s Guide to the Galaxy is a comedy science fiction series created by Douglas Adams. Originally a radio comedy broadcast on BBC Radio 4 in 1978, it was later adapted to other formats, including stage shows, novels, comic book adaptations, a 1981 TV series, a 1984 computer game, and 2005 feature film.
I was most familiar with the video game, which came out about the same time I bought my first computer, the beloved Apple IIc. That might have been in 1986 or so.
Anyway… It is nice to see a new generation of enthusiasts among the current Engineering students.
As data transfer technology progresses, so do cable types. Category 6 UTP copper cable is commonly used today in ethernet installations where 1000BaseT (or gigabit ethernet) systems are required. Cat 6 cable has a certified bandwidth of 250 MHz (500 MHz for Cat6a). Category 6 cable is a newer version of Category 5 and 5e cable wherein the wire pairs are bonded together and there is a separator to keep each pair of wires the same distance apart and in the same relationship to each other. The four twisted pairs in Cat 6 cable are also twisted within the overall cable jacket.
Category 7 cable is much different from its predecessors. It has an overall shield and individual pairs are shielded:
Shields on individual pairs are required to reduce cross talk (FEXT, NEXT). It also requires special shielded connectors called GG45 plugs and jacks. Pinouts and color codes are the same as gigabit ethernet (Category 5e and 6) however, Category 7 (ISO 11801 Class F) jacks and plugs also have to contacts on the corners of the connector or jack. This allows better shielding. A small switch in the jack senses when a category 7 type connector is inserted and switches to the corner contacts, thus keeping jacks and patch panels backwards compatible with Category 5/6 cables.
Category 7 cable is rated for 600 MHz bandwidth (1000 MHz for 7a) which translates to 10 GB ethernet. This was previously the domain of fiber cable. Copper cable has some advantages over fiber; lower propagation delays, requires less complicated equipment, copper is less expensive than fiber and more durable. It is nice to have the flexibility to use copper cable on 10 GB ethernet for runs of 100 meters or less. Longer runs still require fiber.
Category 7 and 7a cable looks remarkably similar to the older Belden multipair “computer cable” pressed into service as audio trunk cable seen so often in older studio installations.
This is a trip down memory lane. Someone has taken the time to preserve and document Radio Shack, its founding, history and all of the catalogs printed from 1939 to 2005. The website archive is Radio Shack Catalogs.
I remember reading these very catalogs cover to cover, when they came out in the mid 1970’s. At that time, this stuff looked expensive and in relative dollar terms compared to today, it was. We had one of these computers in our “Math Lab” in 9th grade:
In fact, when I found one of these computers stashed away in the corner of a transmitter site, I had a flash back of Mr. B scowling as yet another student made a mistake plotting x/y coordinates on the backboard.
Computer audio sound cards are the norm at nearly all radio stations. I often wonder, am I using the best audio quality sound card? There are some trade offs on the quality vs. cost curve. At the expensive end of the curve, one can spend a lot of money for an excellent sound card. The question is, is it worth it? The laws of diminishing returns states: No. High quality reproduction audio can be obtained for a reasonable price. The one possible exception to that rule would be production studios, especially where music mix downs occur.
I would establish the basic requirement for a professional sound card is balanced audio in and out, either analog, digital or preferably, both. Almost all sound cards work on PCI buss architecture, some are available with PCMCIA (laptop) or USB. For permanent installations, an internal PCI buss card is preferred.
Keeping an apples:apples comparison, this comparison it limited to PCI buss, stereo input/output, analog and digital balanced audio units for general use. Manufactures of these cards often have other units with a higher number of input/output combinations if that is desired. There are several cards to choose from:
The first and preferred general all around sound card that I use is the Digigram VX222HR series. This is a mid price range PCI card, running about $525.00 per copy.
These are the cards preferred by BE Audiovault, ENCO and others. I have found them to be easy to install with copious documentation and driver downloads available on line. The VX series cards are available in 2, 4, 8, or 12 input/output configurations. The HR suffix stands for “High Resolution,” which indicates 192 KHz sample rate. This card is capable of generating baseband composite audio, including RDS and subcarriers, with a program like Breakaway Broadcast.
2/2 balanced analog and digital AES/EBU I/Os
Comprehensive set of drivers: driver for the Digigram SDK, as well as low-latency WDM DirectSound, ASIO, and Wave drivers
32-bit/66 MHz PCI Master mode, PCI and PCI-X compatible interface
24-bit/192 kHz converters
LTC input and inter-board Sync
Windows 2003 server, 2008 server, Seven, Eight, Vista, XP (32 and 64 bit), ALSA (Linux)
Hardware SRC on AES input and separate AES sync input (available on special request)
Next is the Lynx L22-PCI. This card comes with a rudimentary 16 channel mixer program. I have found them to be durable and slightly more flexible than the Digigram cards. They run about $670.00 each. Again, capable of 192 KHz sample rate on the analog input/outputs. Like Digigram, Lynx has several other sound cards with multiple input/outputs which are appropriate for broadcast applications.
200kHz sample rate / 100kHz analog bandwidth (Supported with all drivers)
Two 24-bit balanced analog inputs and outputs
+4dBu or -10dBV line levels selectable per channel pair
24-bit AES3 or S/PDIF I/O with full status and subcode support
Sample rate conversion on digital input
Non-audio digital I/O support for Dolby Digital® and HDCD
32-channel / 32-bit digital mixer with 16 sub outputs
Optional LStream Expansion Module LS-AES: provides eight-channel 24-bit/96kHz AES/EBU or S/PDIF digital I/O (Internal)
Audio Science makes several different sound cards, which are used in BSI and others in automation systems. These cards run about $675 each.
6 stereo streams of playback into 2 stereo outputs
4 stereo streams of record from 2 stereo inputs
PCM format with sample rates to 192kHz
Balanced stereo analog I/O with levels to +24dBu
24bit ADC and DAC with 110dB DNR and 0.0015% THD+N
SoundGuard™ transient voltage suppression on all I/O
Short length PCI format (6.6 inches/168mm)
Up to 4 cards in one system
Windows 2000, XP and Linux software drivers available.
There are several other cards and card manufactures which do not use balanced audio. These cards can be used with caution, but it is not recommended in high RF environments like transmitter sites or studios located at transmitter sites. Appropriate measures for converting audio from balanced to unbalanced must be observed.
Further, there are many ethersound systems coming into the product pipeline which convert audio directly to TCP/IP for routing over an ethernet 802.x based network. These systems are coming down in price and are being looked at more favorably by broadcast groups. This is the future of broadcast audio.