Stereo Tool

I just downloaded Stereo Tool to my computer. Works fine. Using the demo mode for now. Have some questions from experienced users.

I am going to use it for AM broadcasting in the USA. I noted a preset for AM broadcasting in the USA which seems like a generic setting since one other setting offers more Bass to the audio processing.

1) Can you tweak the presets for AM in the USA to make the sound suitable for either Talk or Music?

2) Can this software provide Asymmetrical Modulation and exceed 100% modulation? We have some box units that can go as high as 125% for peak modulation which increases the loudness of the station on the AM dial.

Thanks!

Here is a link to two presets I put together for AM Broadcasting. One is for music, one is for talk.
viewtopic.php?f=10&t=23966

StereoTool's presets limit AM Bandwidth to 4.5 kHz by default. In North America, we have a full 10 kHz per the FCC standards (despite most radios rolling off around 5 kHz) and these presets provide for that.

The music one is less aggressive and provides for some more dynamic range while providing some additional equalization for the NRSC mask.

The talk one has a bump around 5 kHz to provide some more clarity and crispness to speech and sound less muddy on the poorly designed radios that are prevalent since the 2000's.

Thanks for the post. I use a Mac but I will see if I can get your presets to work in the Emulator software that I have downloaded to also run Stereo Tools in a Windows platform.

While ST's AM presets are severely bandwidth limited, the setting is easily adjusted. The bandwidth filter is effective, as the program easily fits within the NRSC mask at 10kHz. I tend not to go that high... 9500 at most, sometimes a little lower, but the point is this is not an issue. All of the AM stations I manage generate very clean NRSC reports.

I've tried ST's AM presets and, frankly, don't use any of them, even as starting points. With respect to Hans and his contributors, I don't believe they put a lot of time into AM. Still, the tools are there to make AM sound very good with ST, and I use the program at several stations I take care of.

I'm currently using ST at R&B & gospel stations (where clean, heavy bass is desired), syndicated talk stations, a couple of "vintage standards" music stations, and several Hispanic religious stations, playing a varied format of music and talk. For each of these formats, I started with an FM preset that sounded somewhat close to what I was looking for, then set the bandwidth, pulled out the stereo, and tuned it up for the sound I wanted. After that, I copied the settings over to the other stations within the group(s) playing the same format. Results have been very good. My stations are in markets where Omnia and Optimod products are popular. ST easily compares favorably.

For AM, I'm using a Lenovo ThinkCentre mini computer and a Henry Engineering USB Matchbox II. This combination gives me plenty of horsepower, and a good sound interface that can output analog or AES. The USB Matchbox II has a good noise floor, satisfactory audio and distortion performance and plenty of drive for the +10dBM requirements of most AM transmitters. The combo will fit in a 1RU shelf and leave room for a small Barix box, if you use such things.

As I administer all of my stations from my shop near Seattle, I load Team Viewer and the REA software-based modulation monitor into the computers, This gives me some local control and a virtual mod monitor that works off of a true sample of the transmitter's RF output. Alarms, cameras, EAS endecs and remote controls at the sites are also fully web-enabled.

It could easily take you some time to get the sound you want. ST is a very versatile (read 'complex') program. However,if you have good ears and stick with it, you can get a sound out of your station that will rival any commercial hardware box... and you can keep an eye (and ear) on it from literally anywhere you can get to an online computer.

(edit) Yes. ST has an asymmetry function for your 125% positive setting. I also recommend processing in stereo, using the azimuth correction filter (especially if running older music or tape transfers), then summing the channels in the AM settings page.

I think ST can be adjusted to make any AM transmitter sing. I've had the program running all vintages of solid-state transmitters that have been popular in the US. The last tube-type AM transmitter I have in full-time operation (A 5kW 'Power Rock') runs on one channel of ST. The other channel feeds the station's solid-state standby (a modern, but lower-powered unit). In A/B tests, I would challenge the most golden ears to tell the difference.

RodeoJack. Thanks for the detailed response. A lot of useful information here.

I've found that you have to click the Lowpass frequency setting once click at a time to reach the desired setting. Will have to do this in several sessions otherwise I may end up with Carpal Tunnel Syndrome. Good to know that you can set the high end a bit lower than 10k and still achieve satisfactory sound. I will have to do some on air tests once I receive my new transmitter to see what the best high end level will be.

Surprised to hear that by tinkering with a FM preset you were able to get a more desirable sound on AM. I may try that myself then.

Do you think that the Basic version is adequate for a music station playing Smooth Jazz or AC Oldies provided that the files are either a 16 bitrate for mp3's or .wav files with at least FM quality sound? Or will I need to purchase the Declipper or Delossifier? These seem essential for FM broadcasting but I have had a couple of people tell me they are probably not needed for AM especially the Delossifier provided the recordings are decent.

Also, I take it you are using stereo recordings for the files but then use the Stereo to Mono for AM downmix feature for OTA playback?

You should be able to move the lowpass slider byholding the left mouse key and dragging the slider where you need it. I just checked and it works fine.

On using FM presets: They are a good place to start. You might find you need (want) so move bandwidth sliders around, and change things like attack/release constants, equalizer and clip settings. In any case, I've found a good sounding FM preset seems to be a better place to start than an AM one. It seems the Europeans use 5kHz bandwidth far more than in the US, and the presets in ST tend to reflect it. Also, timing constants are pretty subjective. I have my own criteriae, which doesn't always match up with the stock offerings. Such is the beauty of this software. Unlike some hardware boxes, made by the legacy manufacturers, ST gives you full rein to sound great, or awful. It may take you a while to be really satisfied with your sound. Be diligent in saving your work whenever you make a change. If you do, you can always go back to a previous setting.

What you license depends on what you'll need. For AM, you don't need all of the FM features. If you're playing hot CD material, you may want the declipper. The delossifier may not matter if you don't feed low-grade audio or MP3s to the processor. In any case, none of the features in the system are locked out. Though you may get an occasional nag recording, you can test any part of the software and decide for yourself what you want.

On processing in stereo: Very few of the stations I care for run monaural audio chains. I tend to like that ST can process left/right separately, to the degree you wish. I think the final result sounds better that way. The AM transmitter window has a "downmix to mono" flag, which sends the same mixdown out both left and right sides. If you put ST at the end of a monaural feed however, it will still work well. I'd still tend to feed both the left and right inputs however, as ST seems happier when it's not working with an unused channel.

By doing mono mixdowns and using the USB Matchbox, I'm able to feed (for example) the left output to a main transmitter and the right to an aux. That saves on the cost of a separate distribution amplifier.

Thanks again RodeoJack. I purchased the Basic edition without Declipping or Delossification to start. After a few hours of testing some of my audio files I noted there is little need for Declipping or Delossification at least for now. Once I get my new transmitter and can do actual on air tests, I will know for certain.

Is there a way to control the audio output level on Stereo Tools? I would like to turn down the audio level a bit before it hits the transmitter.

Assuming that you're using the stand alone version: Under I/O -> Sound cards -> FM Output or Normal output.

Alternatively (it's actually not made for this but it will work): Processing -> Post Amp.

Thanks for the tip. I found the slider will allow me to adjust the output level for the audio.