No sound from Sennheiser TV headphones

I use a Roku 3 through a Fosmon audio extractor with it’s optical output to Sennheiser TV headphones.and HDMI on to AVR. Every app EXCEPT Tablo works fine both AVR and headphones. No sound at all from headphones on I use this setup because my wife sews in the media room and likes to watch TV too. She is closer and I need phones to hear over the sewing, especially British, Irish and Australian accents. Anyone have a fix??

You didn’t say if you have the tablo’s 5.1 sound turned on?

Yes important questions:

  1. Is Surround Sound (aka 5.1 AC3 audio) turned on, on your Tablo?
  2. If yes, does your audio extractor “extract” 5.1 AC3 audio to pass through via the optical output?
  3. Do your headphones decode 5.1 AC3 audio? If no, then turn off the Surround Sound on your Tablo. The Tablo will then record future recordings in 2.0 AAC which the Roku will decode to PCM. The Roku doesn’t have an internal Dolby chip so it can’t decode 5.1 AC3 audio.

If 5.1 is turned on for recordings I would turn it off until you can do further investigation/debug. The 5.1 is embedded in the actual recording so those shows already recorded will have this problem.

I guess I’m assuming non-5.1 audio works.

Yes, I have 2 Rokus, a 3 and an express. I am using headphones on the Roku 3. Surround sound is on and I do not want to turn it off as it then turns both Rokus to stereo.

Extractor works just fine on all other Roku “channels”. Fosmon device outputs 2.0 and 5.1 formats, LPCM, DD and DTS Audio.

What is the model of the Sennheiser?

RS-175. I’m thinking it has to do with AC3 being used by Tablo vs Dolby Digital. Thinking about trying a different audio extractor.

RS 175 ( #505563 )

  • Why don’t I get audio from all sources (Netflix, Apple TV, Amazon FireStick, etc)?

Audio coming from certain content providers or devices (Netflix, Roku, Apple TV etc.) typically use an advanced digital audio signal such as HDMI or advanced Dolby audio. These cannot be translated into analog or PCM by most television software and so the signal is not passed through into the headphones. As a result you may get silence or audio from a different source like your cable box.

In order to resolve this, you will you will need to change the audio output format in the app or device to PCM (may be in the smart hub on some TVs) or you will need a digital to analog decoder. The Digital to Analog Decoder will take the advanced digital signal and decode it into an analog signal that your headphones can utilize.

You will not lose audio quality as the digital signal is a carrier signal only. Any audio you hear from your TV speakers, sound bar or headphones is an analog signal. The digital signal is translated by the TV, receiver or other device by the time it reaches the transducers. The only difference is where the audio signal is translated.

If your digital optical output is not in use we recommend the OREI DA34. The OREI DA 34 can be seen here: (

If the digital optical output is already being used by a device like a sound bar you will want the J-TECHDigital to Analog Decoder because it offers both an analog output for the headphones to use and an optical output for the soundbar (or other device) to use. The J-TECH can be seen here: (

Please bear in mind that we recommend these specific devices because we have tested them and know that they work. We do not recommend digital to analog CONVERTERS (a different device entirely) because they cannot translate the more complex digital audio signals.

NOTE: We do suggest looking at your TV’s documentation to make sure that there are no design features that prevent certain digital signals (like HDMI signals) from being output through the Digital Optical output before purchase. It is possible for this feature to exist but exceedingly rare so for most applications the Digital to Analog DECODER is the optimum solution.

More from the manual. The headphones do not decode 5.1 AC3 audio.

Digital audio connection uses incompatible data transmission settings.

Set the digital audio output of your device/audio source to “PCM”, with a sampling rate of max. 96 kHz (see the instruction manual of your audio source)

AC3 is Dolby Digital (DD) audio (they are the same thing). Why do you need surround sound? Are any of your Rokus actually connected to an AVR with a 5.1 speaker setup? I just re-read your initial post and see the answer to this is yes.

I was also reading about a Fosmon extractor and their website says “ Note: Audio cannot play through both optical and 3.5mm ports at the same time, and that priority will be given to the 3.5mm port if both are connected. Audio can be played through one of the optical/3.5mm, and the HDMI output at the same time.”

So make sure nothing is connected to the 3.5 mm (1/8”) stereo port on the Fosmon if you’re using optical output to connect to your headphones.

Finally another option would be to connect the RCA audio output on your HDTV to go the 3.5 mm stereo input on the Sennheiser transmitter using the cable below. Your HDTV can decode 5.1 AC3 audio and likely can output PCM audio over the RCA ports. Or your AVR should have RCA audio output ports as well. What is the make and model of your AVR?

Please note both device links you used show unavailable. To be clear the Fosmon device I use does tap audio from the HDMI BEFORE it goes to my AVR. The Fosmon also passes both audio and video on to the AVR. The AVR sends ONLY video to the TV so the ARC is not available from my Roku. The spsdif from the Fosmon is connected to the Sennheiser R-175 and everything is good EXCEPT when Roku is tuned to Tablo, then no audio. Recap connection:
Roku to Fosmon via HDMI. Fosmon to AVR by HDMI. Fosmon to Sennheiser via optical. AVR to TV by HDMI. Note that connecting Sennheiser to Fosmom headphone jack kills audio to AVR.

I have been using the Sennheiser for a year now with no issues until I added the Tablo app to Roku. The output of my Fosmon is compatible plug and play. For some reason the output from the Tablo app is not compatible. I will likely just avoid Tablo when my wife is sewing.

I have a great home theater setup in our media room. Pioneer elite and 7.1 sound via Boston Acoustics, Sony Blue ray, etc.

Since the audio is also passed through to the AVR via the HDMI, you can connect AVR to the Sennheiser headphones via an RCA cable. You will get audio from the Tablo that way. So it is:

Roku to Fosmon via HDMI, then Fosmon to AVR via HDMI, and then AVR to Sennheiser via RCA cables. The AVR should have composite analog audio output connectors (analog left and right). The link to the cable I provided in my last post is in stock / available.