Sound Cards for Broadcast Use

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 on an excellent sound card.  The question is, is it worth it?  The laws of diminishing returns state: 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 bus architecture, some are available with PCMCIA (laptop) or USB.  For permanent installations, an internal PCI bus card is preferred.

Keeping an apples: apples comparison, this comparison it limited to PCI bus, stereo input/output, and analog and digital balanced audio units for general use.  Manufacturers 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.

Digigram VX222HR professional sound card
Digigram VX222HR professional sound card

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 online.  The VX series cards are available in 2, 4, 8, or 12 input/output configurations.  The HR suffix stands for “High Resolution,” which indicates a 192 KHz sample rate.  This card is capable of generating baseband composite audio, including RDS and subcarriers, with a program like Breakaway Broadcast.

Quick Specs:

  • 2/2 balanced analog and digital AES/EBU I/Os
  • A 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 a 192 KHz sample rate on the analog input/outputs.  Like Digigram, Lynx has several other sound cards with multiple inputs/outputs which are appropriate for broadcast applications.

Lynx L22-PCI professional sound card
Lynx L22-PCI professional sound card

Specifications:

  • 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
  • Multiple dither algorithms per channel
  • Word, 256 Word, 13.5MHz or 27MHz clock sync
  • The extremely low-jitter tunable sample clock generator
  • Dedicated clock frequency diagnostic hardware
  • Multiple-board audio data routing and sync
  • Two LStream™ ports support 8 additional I/O channels each
  • Compatible with LStream modules for ADAT and AES/EBU standards
  • Zero-wait state, 16-channel, scatter-gather DMA engine
  • Windows 2000/XP/XPx64/Seven/Eight/Vista/Vistax64: MME, ASIO 2.0, WDM, DirectSound, Direct Kernel Streaming and GSIF
  • Macintosh OSX: CoreAudio (10.4)
  • Linux, FreeBSD: OSS
  • RoHS Compliant
  • Optional LStream Expansion Module LS-ADAT: provides sixteen-channel 24-bit ADAT optical I/O (Internal)
  • 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.

Audio Science ASI 5020 professional sound card
Audio Science ASI 5020 professional sound card

Specifications:

  • 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.

Breakaway Broadcast

I am a strong proponent of non-computer-based air chain processors.  Something about listening to dead air while the computer reboots is annoying and every computer needs to be rebooted every now and again.

All of that being said, I recently had a chance to play around with Breakaway Broadcast audio processing software.  I have to say, as a low-cost, very versatile platform, it can not be beaten.  I would put it up against any of the high-end FM audio processing, provided one uses a high-quality sound card with an adequate sample rate.

Claesson Edwards Audio has developed several software-based audio processors for a variety of end uses.   They make several recommendations for hardware and operating systems, Pentium 4 3.2 GHz or better, dual-core preferred.  If one is interested in using the sound card to generate composite audio, then any sound card capable of a true 192 KHz sample rate will work.  They list several that have been successfully tested on their website.

For approximately $1,200 dollars or so, one could buy a decent computer, the Breakaway Broadcast software, and the Airomate RDS generator software.  For a Mom and Pop, LP, or community radio station that is looking to do some high-end audio processing and or RDS, that is a good deal.  I would add a UPS to the computer and keep backup copies of the software installed on an emergency computer just in case.  One can never be too safe when it comes to computers, viruses, hackers, and other malicious persons.

Things that I like

  1. Inexpensive, the fully licensed version is $200.00.  The demo version is free but there is a 30-second promo every thirty minutes.
  2. There are several factory presets, but everything is fully configurable, changes can be named and saved allowing some experimentation.
  3. Audio cards with 192 KHz sample rate or greater can be used to generate composite audio, eliminating the need for a separate stereo generator
  4. RDS capable with additional software (Airomate2, approximate cost $35.00)
  5. The same processing computer can be used for streaming audio and or AM audio processing simultaneously.
  6. A full set of audio calibration tools for AM and FM transmitters allows correction for tilt, overshoot, and linearity.  Can add pre-emphasis at any user-selectable rate.
  7. Fully adjustable phase rotators.

Things that I don’t generally like:

  1. A computer-based system using Windoze operating system

WXPK in White Plains, NY has been using this software to process their streaming audio for about 2 years now.  The software itself is extremely stable running on a stand-alone Windows box with XP service pack 2.

How expensive is online radio these days?

iphone 3GS

I read a very good and interesting post on James Critland’s blog.  He is somewhat concerned about the trend for mobile wireless providers to no longer offer unlimited data service for a flat fee.  I find it interesting that all of these companies seemed to have reached the same conclusions at the same time.  But anyway…

The general surmise of James’ post is that the average person will not be able to afford online radio through a 3 or 4G device because of the limited minutes available and the additional charges incurred.  (35 quid is about $50.00) To make that meaningful to a US audience, I decided to redo some of James’ math.

Iphones are primarily serviced through ATT.  ATT has two different data plans that are coupled with voice plans in a bundle.  For example, a 450-minute voice plan and a 200 Mb data plan will cost $55.00.  A 900-minute voice plan with a 2 Gb data plan will run $85.00.

Here are a few interesting tidbits and some good math:

  • A 64 kbps stream runs 7.68 kb per second, or 460 kb per minute (1 kilobit per second = 0.12-kilobytes)
  • 1 hour of online listening equals 27,640 k bytes of data transferred
  • The 200 Mb plan cost $15.00 with voice plan, the 2 Gb plan cost $25.00 with voice plan
  • The 200 Mb plan would allow for 7 hours of listening time if no other data use occurred
  • The 2 Gb plan would allow for 72 hours of listening time if no other data use occurred
  • Beyond those data transfer amounts, extra charges are incurred

Almost 50% of the time spent listening to all radio sources (terrestrial, satellite, online) is in the car.   The average person in the US listens to the radio for about 3 hours per day or 90 hours per month.  Half of that time would be 45 hours or so.

Clearly, anyone who is more than a casual listener of online radio will need the 2 Gb plan.  However, given the paucity of entertainment available from traditional radio sources, this is not an outlandish amount to pay.  I remember in the ’70s when folks were saying cable TV would never catch on.