Pi 3 Sound – It’s The G-Damn HDMI Adapter

For a few years know I’ve not been able to get stereo sound (or any sound) out of my Raspberry Pi boards. From the Pi 2 to the newer Pi 3. About a year? ago got a clue it might be that the combo of an HDMI cable and DVI adapter might be the problem. More recently found that HDMI protocol has a secret handshake thing it must do or it just doesn’t work. I have no idea if my adapter does that right, but I do get video through it, so I guess so.

OK, I’d basically given up on using the Pi 3 as a media station and moved the Chromebox over to do that (it works great BTW). Then added a Roku to the TV so getting Kodi going is kind of way back burner for me, now.

Still, it nagged at me. Other folks seemed to get sound out of the Pi OK, why not me?

Well, today that “round toit” landed in my lap. I took down my computer set up, moved the Pi Dogbone Stack to the bedroom. Connected the HDMI cable to it instead of the Chromebox. Added a dropcord for power. Fought with networking for a while (move from wired to wireless, had to comment out eth0 to force the gateway wireless). Fired it up. Got the TV happy on aspect ratio. Posted some comments.

Then launched Youtube.

At first, didn’t hear anything and thought “Crap”… then noticed some soft sounds of Lady Gaga Edge Of Glory at the limit of my hearing. Grabbed the remote… Oh, so the signal out is ‘way soft’, got it. I presently have the Toshiba set to “62” on the volume and it is “OK” not loud. Normally I run it at 9 with occasional use of 12 to 14 on very soft TV. The occasional 20 ish on things that are abominably soft. But I have sound!

Conclusions

It isn’t about me configuring sound wrong. I didn’t need to do anything to make the sound part go other than plug in a real HDMI cable to a real HDMI TV.

The Pi 3 has a very low signal level on the output. I have no idea if that is configurable or just “live with it”. Don’t really care much, though.

While I could use the Pi 3 to drive the TV, I’m happier using the Chromebox. It’s already sunk cost so that it runs about the same as 6 Pi boards doesn’t matter. The sound out levels are fine already, and I can easily use my bluetooth headset with it. It’s small enough and has fewer connections needed (using an integrated bluetooth compact sized keyboard and trackpad…) and looks nice with the TV. Were I going to run a video system like Kodi to get loads of stuff without legal niceties, I’d look to the Pi, but I’m not doing that.

I need a new HDMI based monitor. The one I have is OK, but it’s about 15? 20? years old already. Originally the old PC video in, and the DVI was there but I never used it. That’s how old it is. For about $100 I can get a nice similar sized HDTV (720p or 720i) and be done with it; while getting TV at my desk too ;-) Solves the sound problem. Solves the TV in the office problem. Lets me move the old monitor onto an old computer instead of swapping cables. I’ll likely do that in a 1/2 a year or so, if it ever really reaches top of the issues pile.

And, the biggie, IF any one is having “sound problems” with a Pi, make sure you plug it into a real HDMI TV first to sort out that “it isn’t you” and it’s the monitor / cable / adapter…

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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6 Responses to Pi 3 Sound – It’s The G-Damn HDMI Adapter

  1. Larry Ledwick says:

    You might be able to solve your low audio problem on the RPi with a very simple amplifier.
    The LM386 is really really simple to work with. It will happily go ultra sonic on the audio so a simple RC filter to kill the ultra high frequencies can be useful in some situations. Other than that the basic layout used only 2 caps and 2 resistors (one a pot on the input)

    See page 8 here:
    http://www.ti.com/lit/ds/symlink/lm386.pdf

    I have used it to build simple audio amplifiers. If you need a bit more power the TDA2002A is equally simple to play with.

    Both chips are dirt cheap. (about 20 cents each if bought in lots of 20, single just a couple bucks on amazon)
    I imagine your local electronics outlets have bins of them for about 50 cents a piece.

    You can buy a complete pre-fab amplifier for under $4.00
    https://www.amazon.com/Amplifier-Board-TOOGOO-Modules-Speaker/dp/B011BHFFGY/ref=sr_1_26

  2. E.M.Smith says:

    I appreciate the pointers to amplifiers, but I’m happy to just turn up the volume control ;-)

    Basically, I was mostly wondering why I was not getting the audio configured right, until I figured out it might not be software or configuration. Today was used to prove it was a hardware issue and in particular the adapter to a non-HDMI monitor. Just scratching a question itch.

    Going forward, I’m likely to get a new monitor mostly because this one is way old and the only things that use that interface are all in archival storage. My old PC pile… That it would also let me play YouTubes on the R. Pi instead of reaching over for the tablet would be a small benefit but nice to have.

    I have no need to drive the Toshiba TV with it at this time. I can drive it with the Chromebox nicely, and I’ve learned to “cast” my tablet to the Roku…

    Mostly I posted this just so anyone who is having trouble with Pi Sound might have an idea what to test so as to avoid the long lag I had in figuring it out.

  3. Larry Ledwick says:

    Understand, I have run into a few online videos where the audio level is low enough that even with the system audio at 100% they were marginal. If you can get enough audio level by cranking it up, that solves the problem.

  4. Steve C says:

    The HDMI output is the main thing that has stopped me from getting into the Pi since it first appeared. I haven’t had a TV in the house for over 30 years, and all my monitors are 15-pinners, so … also, no PCI socket to plug in my cool M-Audio soundcard with the 1/4″ balanced-line connections, so … :-(

    @Larry: The ‘386 and 2002 are OK amplifiers, but (if you can find one – the chip is 20 years old!) my favourite is the TDA7377,. It has 4 power amps in a 15-pin flatpack, two of them being phase-inverting so you can make up two (10W 0.03%THD) bridged amps just by soldering the (adjacent) input pins together. Also, designed to work on a nominal 12V rail, so a good option for that ‘Disaster-Ready’ audio system. Worth looking out for.

  5. Larry Ledwick says:

    @Steve C

    Thanks will look into that TDA7377! Last time I fiddled with the TD2002 and LM386 was in the late 1980’s early 1990’s so lots of chips have changed – been dropped or superseded.

    It is a bit higher power than most of my “low power” disaster operations needs require, but would work well for things like the computer desk top speakers if you want to rattle the windows a bit ;)

  6. @Chiefio,
    I have a copy of the HDMI version 1.3 specification which runs to 237 pages (2 MB). It includes the details of the handshaking you mention. This document was issued in June 2006 so I looked for something more up to date. Here is a link to an update that was issued in November 2006.
    http://www.fpga4fun.com/files/HDMISpecification13a.pdf

    I was able to find a version issued in September 4, 2013. It is 8 pages longer than version 1.3 so it seems likely that something significant has been added:
    memp.qiniudn.com/Meekdai.com_HDMI_Spec_2.0.pdf

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