I’ve connected my radio to the QMT-1B and it works, but the audio sounds "tinny" and it doesn’t have much bass. What can I do to fix that?
The question this article addresses – that “tinny” audio problem – can be fixed right at the QMT-1B before the Signal Quality (FM Noise) measurement.
Here’s why you’re likely hearing “tinny” audio:
Since the QMT-1B uses the noise component of the receiver audio to measure FM audio quality, the built-in conditioning or noise reduction used by some newer receivers actually interferes with a good FM Noise measurement by the QMT-1B. That, in turn, means you aren’t hearing the best audio quality.
How to fix this:
Step 1: Use Discriminator Audio
Audio conditioning by the receiver is usually done at a point after the discriminator. Therefore, the solution to the “tinny” audio problem is to have the QMT-1B use the discriminator audio of the receiver directly instead of the line or speaker audio output.
Step 2: Use theQMT-1B’s FM De-Emphasis Filter
If done on its own, using the discriminator audio directly can result in a “harsh” or “bright” audio result. Since that’s also not ideal, the QMT-1B has a built-in FM de-emphasis filter.
When you connect to the discriminator audio and enable the FM De-Emphasis filter, the filter will act on the audio after the discriminator (after it samples the audio). That means it will affect how audio sounds to you, but it will not interfere with the QMT-1B’s audio noise sampling.
Although the need to use the discriminator audio is uncommon, the FM De-Emphasis filter on the QMT-1B provides an easy-to-implement solution.