Troubleshooting my Audio

**TomL8345** · 11-26-2018, 10:48 PM

I am running an RPi w FPP 2.4 to a small Chinese USB FM Transmitter, basically the same set up I used last year. Last year I had my Pi and Transmitter in my 2nd story office overlooking my show and it sounded great.

This year I have moved my Pi out into the yard and of course, the FM Transmitter came with it, I am now getting horrible static that comes on when I start a sequence and ends as soon as the sequence stops. The audio is there, but it is way down low. My USB Transmitter is attached to the Pi with a 10' cable so I can get the transmitter away from other electrical items. I had orginally included the Pi in one of my main controller enclosures, but moved it out today so it is in an enclosure of its own, this made 0 change to the sound quality.

Suggestions?

**aknflyer** · 11-27-2018, 03:19 AM

Something changed starting on v2.x. I was working with Dan Kulp for a bit, but then with christmas coming up I think he got busy. As a workaround I used a usb sound adapter and connected the audio from that with a stereo cable to the dsp pll transmitter. I do have a better soundblaster 3 shipping, to see if that audio is a little better quality as others have posted. I will attach my settings page.
Settings.jpg

**jtrpop** · 11-27-2018, 12:24 PM

Be sure to set volume to 70 when using the Sound Blaster Play 3 or FPP will clip the output. I made a quick and dirty impromptu video on setting correct levels which applies to any sound output or FM transmitter as many this year are having sound issues, regardless of their setup. Also forgot to mention turn off any EQ, & turn down or off any Mic input: https://youtu.be/FfW9airaXiU

**aknflyer** · 11-28-2018, 01:19 AM

I did set the levels with test equipment, I am a telecom technician and have all the tools of the trade. It just does'nt sound as clear as it did via the usb.

**aknflyer** · 11-29-2018, 03:08 AM

I received my soundblaster 3 today. I can say the output level is much higher. After installing, the levels to the transmitter are much higher. Signal to noise ratio is much improved. I was able to reduce the transmitter modulation a bit. Helps with the quiet parts between sequences. I agree this adapter is much better than the generic audio adapters. A setting on 70 on the pi is just about right. So jtrpop is correct on his advice.

**TomL8345** · 12-03-2018, 03:12 PM

I tried setting my volume to 70 and even as low as 50 and absolutely no change to my audio. I should be getting a SB Play 3 today in the mail, so I am going to go through that to my dsp pll transmitter. I notice that when the dsp pll transmitter boots up it shows "HI" on the lcd. Is that referencing the Gain, and is there a way to set it to low? I have found no mention of gain on the scant documentation I have been able to find for this device.

**jtrpop** · 12-03-2018, 05:24 PM

Originally Posted by TomL8345

I tried setting my volume to 70 and even as low as 50 and absolutely no change to my audio. I should be getting a SB Play 3 today in the mail, so I am going to go through that to my dsp pll transmitter. I notice that when the dsp pll transmitter boots up it shows "HI" on the lcd. Is that referencing the Gain, and is there a way to set it to low? I have found no mention of gain on the scant documentation I have been able to find for this device.

If your output source sounds fine when headphones are plugged in, you are likely over driving your FM transmitter. When you get your SB Play 3, turn off Pi, plug in, turn on, select it on config menu, set FPP volume to 70. Follow instructions in the video I posted above to optimize your levels. As for transmit power, if you have the Signstek or similar variant: Before plugging in the unit, press and hold the power button. Plug in the power and continue to hold for 3 seconds, then release the power button. The up/down buttons now allow you to select the power setting (defaults to "High" power).

**TomL8345** · 12-03-2018, 09:05 PM

Originally Posted by jtrpop

If your output source sounds fine when headphones are plugged in, you are likely over driving your FM transmitter. When you get your SB Play 3, turn off Pi, plug in, turn on, select it on config menu, set FPP volume to 70. Follow instructions in the video I posted above to optimize your levels. As for transmit power, if you have the Signstek or similar variant: Before plugging in the unit, press and hold the power button. Plug in the power and continue to hold for 3 seconds, then release the power button. The up/down buttons now allow you to select the power setting (defaults to "High" power).

Thanks for the input. In the meantime, I pulled out my FM-02 and dipole antenna (but tuned for a different freq, I am on 95.5 and this was tuned for 97.9), but it sounds great so I will probably leave that dog lie until next season.