gmbartlett
New member
I've never been happy with the sound quality of the FM02 transmitter being driven by the Helix MP3 player. There is a lot of "white noise" that almost drowns out the actual music. I've always assumed that it was a problem with the inexpensive FM02 since the sound quality of the Helix through headphones or amplified speakers was great. However, some Helix users have pointed out to me that the FM02 sounds great when driven by other MP3 players. So I tested it with my Galaxy S phone and was able to get pretty good sound out of my FM02. I did some tests and determined that the peak to peak voltage output of the Helix MP3 player is about 9 times greater than the peak to peak voltage output of my phone. I tried reducing the volume on the Helix MP3 player but found that it greatly distorts the signal. Next I tried adding an inline volume control between the Helix and the FM02 and that worked great.
So if you want to improve the sound of your Helix through the FM02 you should add an inline volume control. The one I tested is available through Wal-Mart for less than $8.00. The link is: http://www.walmart.com/ip/Koss-In-Line-Headphone-Volume-Control/11051681. Just put this volume control between the Helix and your FM02 and turn it all the way up. Next start the Helix with a playlist playing a sample MP3. Listen to the output on an FM radio and slowly turn the volume down until the "white noise" goes away and you have a clean sound.
Here are a couple of other tips to improve the sound:
1) The FM02 has a bandwidth of 100 Hz to 15,000 Hz. You can use Audacity (http://audacity.sourceforge.net/) to filter out the frequencies in your MP3 that fall outside of that band. Use the Low Pass Filter effect set to 15,000 Hz and the High Pass Filter effect set to 100 Hz.
2) Most songs have very quiet parts and very load parts. You can use the Compressor effect in Audacity to boost the quiet parts and attenuate the loud parts so the overall song sounds musically better by controlling maximum levels and maintaining higher average loudness. I use the default settings on the Compressor effect with pretty good results. However, you can tweak the settings to your preferences.
3) The final suggestion is to use MP3Gain (http://mp3gain.sourceforge.net/) to equalize the overall volume between all of the songs. After you have filtered and compressed the MP3s then move them all into a single directory. Then run MP3Gain on the directory using the Track Gain option. This will equalize all of the MP3s to the target volume.
Apply these three tips in that order and you will improve the overall quality of the audio on the Helix.
So if you want to improve the sound of your Helix through the FM02 you should add an inline volume control. The one I tested is available through Wal-Mart for less than $8.00. The link is: http://www.walmart.com/ip/Koss-In-Line-Headphone-Volume-Control/11051681. Just put this volume control between the Helix and your FM02 and turn it all the way up. Next start the Helix with a playlist playing a sample MP3. Listen to the output on an FM radio and slowly turn the volume down until the "white noise" goes away and you have a clean sound.
Here are a couple of other tips to improve the sound:
1) The FM02 has a bandwidth of 100 Hz to 15,000 Hz. You can use Audacity (http://audacity.sourceforge.net/) to filter out the frequencies in your MP3 that fall outside of that band. Use the Low Pass Filter effect set to 15,000 Hz and the High Pass Filter effect set to 100 Hz.
2) Most songs have very quiet parts and very load parts. You can use the Compressor effect in Audacity to boost the quiet parts and attenuate the loud parts so the overall song sounds musically better by controlling maximum levels and maintaining higher average loudness. I use the default settings on the Compressor effect with pretty good results. However, you can tweak the settings to your preferences.
3) The final suggestion is to use MP3Gain (http://mp3gain.sourceforge.net/) to equalize the overall volume between all of the songs. After you have filtered and compressed the MP3s then move them all into a single directory. Then run MP3Gain on the directory using the Track Gain option. This will equalize all of the MP3s to the target volume.
Apply these three tips in that order and you will improve the overall quality of the audio on the Helix.
