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[SOLVED] Sennheiser RS120 static burst auto power OFF solution

Sennheiser RS120 On-Ear Wireless RF Headphones

I was concerned by negative reviews on this product, especially regarding the static blast after an automatic power OFF "feature": a few minutes after stop of audio input, the base unit shuts off, and the headpnoes start emitting white noise (static) and the volume the headphones are set to. I have contacted multiple departmnets of the manufacturer multiple times, and they have explicitly refused to provide details on how to disable the stand-by function.

Although I was capable of disassembling the product, attempting to reverse-engineering it at the circuit level, and doing DYI electronic repair to attempt to "fix" the product, I also have the amazingly powerful Linux OS at my disposal. So I fixed the problem by software.

The idea is to output a short "silent" tone from the OS which will periodically reset the APO circuitry of the base station.

The steps are as follows:

1) Use Linux Mint Cinnamon. If you are using Windows, it is time to switch to Linux. It is EASIER and BETTER.

2) Use Audacity to generate and test a "silent" tone at the low or high extremes of the audio range (claimed to be 20Hz thru 20kHz). Unfortunately, unlike with wired headphones, high frequencies inputted into these headphones produce unexpected results (different and very audible pitches are produced at 17kHz thru 25+kHz). You may continued experiementation, but for an "inaudible tone" I went with a 10Hz, 2 second. If this is audible for you, or if this interferes with the playback, or if you want to experiment with a shorter tone, feel free to do so and let me know.

3) Save the tone as a .wav file or similar.

4) Create a shell script to play the .wav file with "aplay" or similar.

"/usr/bin/aplay /home/YOURUSERNAMEHERE/10Hz_2sec_tone.wav"

5) Place the shell script and the audio file in an accesible directory, such as your Home directory.

6) Create a crontab entry (use How to create a weekly database backup Cron job as a reference) for a task to be run every minute (* * * * * *):

"* * * * * /bin/bash /home/YOURUSERNAMEHERE/cron_play_silent_tone.sh"

Alternatively, you can bypass the .sh script and execute the aplay command directoy in cron.

My files are available here: www.MKRD.info Sennheiser inaudible tone cron files.zip

After one particular logon to my computer, cron appeared to not work. After a great deal of troubleshooting, it appeared that aplay was attempting to play the file, but no audio output was being generated. Only a computer restart solved that problem. If it persists, I will let you know.

You are not on a PC? If you can DYI electronics then you can try building a 555 circuit in an Altoids tin can which produces a 0.5V 1 second click every minute, to similarly periodically reset the APO circuitry. Or you could try to disassemble the basestation and we can reverse engineer the circuitry.

Let me know how it goes!

Update: In about 10% of logon cases, cron aplay does not produce a sound even though the aplay task fires off and system manager shows cron task as running. So far, I am only able to resolve this with a computer reboot. Let me know if you find out the cause.

Update 2: The reliability of this solution has been steadily decreasing over time (couple of years). First it dropped to about 1/3 of logon times to result in script not running, to what it now feels like 50% of times when I logon to my computer, script is not running. Lately, it seemed to have broken completely. As usual on Linux, many hours of searching on obscure forums etc later, I found out that logs relevant to this can be read from:

/var/log/syslog

Which was being polluted with entries like:

pulseaudio[4928]: [pulseaudio] protocol-native.c: Warning! Too many connections (64), dropping incoming connection.

I have even tried replacing aplay with other solutions in my bash script, like

/usr/bin/paplay /home/linux/10Hz_2sec_tone.wav

Then after A LOT of circumstantial evidence, it seems like having Firefox with MANY (less than 100) tabs opened, with a good percentage of them being YouTube tabs, saturates all 64 available connections to PulseAudio, and cron fails to play the audio file. You can test this by closing Firefox, and waiting for cron to run its scheduled task.

Unfortunately, no matter what you use on Linux as a top-level command (aplay, paplay, whatever), they all go thru PulseAudio etc. Also strange is the fact that I can play audio thru VLC even when Firefox is tying up these "connections", whatever they are, yet cron fails to wrestle a connection from PulseAudio for itself.

Seeing how buggy these multiple layers are on Linux, I am looking at a replacement for cron, something that is guaranteed to run, is configured by a GUI, and gives me GUI indication of its running. Something like a system tray utility...

Argh!!!!!!

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