CircuitWerkes / CW Broadcast
ST-EXT1 Cost Effective Broadcast Audio Processor


Professional audio processing used to require dedicated specialized electronics and it cost a lot to do it well.  Since the 2000s, audio processing software has been competing with the dedicated electronic platforms.  Some of the software has matured so well that it sounds as good, or even better, than the hardware platforms costing $10,000 or more.  Best of all, some of the software will run on a dedicated Single Board Computer, like a Raspberry Pi.  One of the best processing software suites on the market is Stereo Tool by Thimeo. Stereo Tool is a multi-band compressor/Limiter with advanced and unique features.  This software is already in use at over 4000 FM broadcast stations.  Stereo Tool includes stereo generator and RDS in all versions.  When run on a Raspberry Pi, Stereo Tool is limited by the Pi sound card. Our ST-EXT1 adapter gives you balanced audio inputs that can accept +10dBm inputs without distorting.  The main audio output is on a standard BNC connector that can be configured for either balanced or unbalanced operation.   The ST-EXT1 includes a Raspberry Pi 4 or 5 and a fully licensed copy of Stereo Tool.  Everything is set and tested at the factory and shipped to you, ready to go on the air.

 
All basic Setup is already done for you

We have configured the Pi and its Linux OS for you.  When you get the ST-EXT1, you can literally connect just the audio inputs from your source and then connect the composite output to your transmitter and it will work. 


Stereo Tool is fully configurable by you

Of course, most users want to customize their audio processing for their formats and audience tastes.  Stereo Tool has both simple and detailed controls that can be accessed by the internal Webserver.


Above: Stereo Tool Processing Overview Page


In the processing overview area are a handful of sliders that can be used to customize your station's sound.  You can get louder, softer, denser add bass, treble, midrange or whatever you need to make the station sound its best. For many users, these controls are enough to get the precise sound that you want.   For those that want to dig deeper, Stereo Tool lets you setup all of the following features:

  • Dehummer
  • Automatic Gain Control
  • Low Level Boost
  • Multiband compressors
  • Stereo effects
  • Immersive Bass
  • True Bass
  • Streaming final clipper
  • IceCast / ShoutCast stream
  • AM processing
  • FM Stereo / RDS / RDBS
  • FM ITU-R BS.412 limiter
  • Bass Clipper
  • Simple Clipper
  • Advanced Clipper
ST-EXT1 Back Panel
Professional Hardware Features Make Interfacing to Your Station Easy
The ST-EXT1 has balanced left and right audio inputs on pluggable screw terminals, An AES-3 balanced digital input is also provided.  Two analog composite outputs are provided.  The main composite output is jumper select-able for balanced or unbalanced operation.  Boot up time is less than 60 seconds and Stereo Tool is fully configurable via its built in webserver. 

Stereo Tool is available with one of two different licenses:
The ST-EXT1 can be ordered with the Standard FM or the Professional FM license.  Standard FM includes two multiband compressor/limiters, EQ, advanced limiter, stereo generator and RDS.  Professional FM includes the unique distortion cancelling composite clipper, advanced RDS & more.  Professional can sound slightly louder, but both sound great on the air. 
Free Lifetime Upgrades

Registered owners of Stereo Tool receive free software upgrades for life.  If a new feature is released or improvements are made, you can run the latest version of the software, even if it is released five years later.


Main Features at a Glance:

  • Balanced left and right audio inputs
  • AES-3 Balanced Digital input, supports up to 192kHz  (L and R only, no composite)
  • Two electrically separate composite outputs on BNC jacks.
  • Composite Output 1 can be jumper configured for balanced or unbalanced mode. 
  • Includes a Raspberry Pi-4 or Pi-5 with a licensed copy of Stereo Tool
  • Available with Standard or Pro License
  • ST-EXT1 with the Standard license is $1,199
  • The standard license includes stereo and RDS. In most markets, this license will make you one of the louder stations on the dial.
  • ST-EXT1 with the Professional license is $1,599
  • FM Pro adds special  Composite Clipping to the processing. The Composite Clipper takes the stereo pilot, stereo encoding & RDS into account when generating the composite MPX signal, which increases the headroom for audio by several dB's. You can typically generate a signal that's 2-3 dB louder without sounding more clipped.
  • Customers that buy the standard FM license can upgrade to the pro license at any time by contacting us to pay the difference.   Other paid software features like the declipper and delossifier can also be purchased ala carte later, as needed.