I mainly focus on my 92.9FM signal which uses stereotool DSP in winamp for audio processing and does a damn good job. However, for my 1620kHz station, I haven't found any good audio processing and wonder what you guys think? Any good free programs out there for zara radio?
If you're using Zara v1.6 or newer, it doesn't support plugins. Might have to use outboard hardware if the PC doesn't have the power to run virtual cable and other processing.
A-Train ... Can you get your hands on a cheap used Craigslist computer?
With a decent soundcard going in and out, you can make use of free audio processing software such as StereoTool 8.40 ( http://www.stereotool.com/)...
MBProcess ( http://hornplans.free.fr/mbprocess.htm)...
or Limiter No. 6 ( https://vladgsound.wordpress.com/plugins/limiter6/).
If you can nail down a Linux computer, use the free CALF plug-ins ( http://calf-studio-gear.org/) to daisy chain a Gate/Multiband Compressor/Limiter and just start fiddling with the settings.
It means you now have to connect your Zara output to a second noisy, hot computer running in your studio space, but it's a fully-fledged dedicated audio airchain processor you can adjust to create your own signature sound, and not just a limiter plug-in with one sound. Good luck.
Since it wasn't said otherwise we guess that Atrain is feeding the same audio to both FM and AM.
Stereo Tool does a super quality job on FM, as was said.
Did you know that Stereo Tool also contains a professional AM processing section including NRSC Equalization?
Therefore by running two instances of Stereo Tool you could solve both FM and AM.
To the best of my experience Stereo Tool can only run once per computer therefore you would need a dedicated computer for the AM instance of Stereo Tool, and since your playlist is already running your programs you could use the Stand Alone Version of Stereo Tool on the AM side.
I can say some decent things about SONOS 4 as well --- once upon a time a paid-for product, then released briefly for free before being re-engineered as a new paid-for product.
Its a narrow window, but the free version is still available thru the Jan 10 2015 snapshot of www.burnill.co.uk at web.archive.org
And you'll really need to do some digging for this one, but there is also the three-band Broadcast Processor from Jeroen Breebaart. It's a bit rough around the edges and can sound harsh in the upper end, but I think you can still grab it from VST4Free.
Download Sonos 4.4.5.0 from Cnet which I was able to actually Download it.
http://download.cnet.com/Sonos-4/3000-18504_4-75415522.html