Commonly around here for AM broadcasting see the Inovonics 222 recommended for post processing pre transmitter.
Was wondering if there are other processors folks use to accomplish much of the same as the Inovonics 222? Issue is the Inovonics aren't real abundant in used markets currently, nor are they cheap.
In a recent posting John WDCX shared his discovery of a substitute for Inovonics 222 and it is a wonderful secret...
It's a recent version of StereoTool by Hans Van Zutphen, available from his website.
I am married to my Stereotools DSP Plugin, which provides professional audio processing.
But the version you want is called the "Stand Alone Version" which has the special processing that matches the Inovonics 222 (asymetric modulation). .
There is also a VST Plugin Version, but I do not know if it has the asymetic modulation.
StereoTools looks nice but I am going to need to find some directions for getting it to work under Linux properly with Jack and how to route the auto through the processor.
I was blindly trying this DIY style and it was really pounding CPU and I wasn't hearing noticeable changes in the audio as I changed settings.
The StereoTools licensing has me confused. For what us AM broadcasters need, what would the StereoTools licensing cost?
Also found a Behringer processor stack recommendation from one the popular Part 15 transmitter manufacturers (instead of the Innovonics 222). Looking into that gear also.
All new to me 🙂
New information has come to light since mentioning that Stereo Tool provides a workaround way of achieving 125% asymetrical modulation...
This fact was first reported by John WDCX and my thread above was not correct... the Standalone Version is not the only version that has this remarkable ability.
As both John and I discovered, ALL recent versions of Stereo Tool can do asymetric modulation, but in some versions one must figure out how to open the Advanced Configuration Menu.
For the past week I've been driving my AMT3000 modified (large loading coil) SSTran Transmitter with 125% modulation, and it really jumps out of the radios.
At last night's ALPB Meeting Member Radio8Z made an important comment... he said that for the asymetric modulated audio to function properly the polarity (relative phase) of the audio line and transmitter circuit would need to use "absolute polarity" ... that is to say that if the polarity were flipped (inverted) it would fail and sound terrible.
The reason my (AMT3000) system works so well is that Hans Van Zutphen, author of Stereo Tool, designed his processor so that the positive audio polarity is placed on the center tip of the audio line outputs. ALSO, PhilB, inventer of his AMT3000/5000 Transmitters used professional standard audio to modulation polarity.
The AMT3000 is fed by a direct wire connection which preserves audio phase integrity all the way down the line.
HOWEVER, my other system, the STL (Studio Transmitter Link) feeding the AMT5000 evidentally has an audio signal inversion, resulting in very tinny, low modulation.
That audio circuit exits the computer by USB Audio to a USB WiFi Transmitter, received in the other room by a WiFi Receiver with internal digital to audio conversion, and into the AMT5000.
Unbalanced audio lines cannot be flipped to change polarity, it will be necessary to transform to a balanced audio line so the positive and negative can be switched.
An even more detailed discussion of setting up Stereo Tool will become available in the "How To" section at the alpb.com.
check your domain i think it has been hijacked. it no longer seems to point to the ALPB website.
I find TheALPB.com seems to be fine. I did a refresh of my browser to be sure.
I'm curious to know where the link takes you. Check your link address.
Here at Worldround Radio we checked the link to ALPB and it's good.
It can be found at
The immense switchboard you will see connects to a million part 15 locations in the world.
Thus we must ask, Robert kc8gpd... what are you saying?
there was my mess up. didn't put in thealpb just plain alpb
Thanks to Friend Carl for his sucinct write-up. I may also add that for whatever reason, one can select negative excursions as well so be careful when setting up Stereo Tool thought the default is posivitive at 125%.
I've taken several negative excursions.
Since first reporting about it earlier in this thread, I've been driving the AMT3000/custom-loading-coil/Wintenna combination, with 125% asymetric modulation supplied by Stereo Tool the Winamp DSP Plugin, with NRSC Pre-Emphasis jumpered in the AMT3000.
Today I've turned off the 125% asymetric but will keep the Pre-Emphasis.
WITHOUT the AM Pre-Emphasis, while listening on a portable outdoors, speech is only understandable within about 6-feet, whereas WITH Pre-Emphasis the same speech can be heard 20 or more feet away from the radio.
The Stereo Tool asymetric modulation works as well as a hardware device, and achieves the desired result with capable transmitters, such as the AMT3000 and AMT5000.
But for local listening where I'm not competing against other stations, there's no benefit to the extra loudness, since I listen to my station either way, and can simply use the volume control on the radio.
Also, and I'd enjoy comments on this, but I think the extra modulation is of most benefit with loud music, making loud louder.
Talking voices have natural variation in loudness, and making them louder ends up being a matter of whether the listener adjusts his volume up or down, which he would do in either case.
But once I get a feel for what it's like turned off, I might decide to turn the asymetric back on.
I plan to get started on my ground mounted Rangemaster project this weekend. It will in turn be driven by the StereoTool processor. I will report my findings on Monday.
John WDCX how is your new AMT5000 coming along?
Back Burner for now.
This morning a listener with excellent ears let me know that sibilants coming from KDX Worldround Radio on our Shoutcast and Icecast streams had a fuzziness that was not like the good audio she's heard from us in the past.
Going into Stereotools and monitoring my stream from the online stream, I heard what she heard, and attribute it to all the fiddling I did within Stereotools to achieve AM Asymetric 125% modulation.
To RESET I selected the Stereotools BYPASS button and am now streaming files AS IS, depending on whatever processing the producers may have added to their programs.
In this RAW state the program files are all over the place. Some producers compress for maximum level of everything and some producers ride very low on the VU scale.
But for now the fuzzy sibilants are fixed and I can start looking for a favorable Stereotools setting that will favor the audio streams.