SDS100/SDS200: SDS100 - Headphone Jack is Wired Out Of Phase - Uniden Support Notified and Temp Fix Made

[MarkyM]

I just received my new SDS100 and noticed the first time I plugged in a pair of stereo headphones that the headphone jack (which is a stereo 3.5mm TRS jack) has the 2 channels wired out of phase. There's an older thread about this from 2019 but is closed.
The same headphones receive a normal in-phase signal from my BCD160DN.

This is interesting because since 3.5mm stereo headphone jacks use a common ground for both channels, and the SDS100 is really a mono device, the headphone amp chip in there must have separate grounds for each channel. Like a quasi-balanced output.

I have emailed Uniden Customer Support asking them to forward it to their engineering team.
We'll see what they have to say. I have copied the email I sent to them below.

For now, I have constructed an adapter cable which connects the tip of the 3.5mm plug to both the tip and ring of the 3.5mm jack. This routes the output of one channel from the SDS100 to both headphone channels. It is working perfectly and sounds just fine. No straining or overload detected with multiple headphones. Here's a photo of the adapter cable:



And here's the email I have sent to Uniden Support:

Hi,

Let me preface this by saying that I’m an audio and broadcast engineer in my professional life.

I just purchased a new SDS100 and it is a fantastic scanner! With a lot of help from YouTube videos and the Radio Reference forums, I had programming setup in Sentinel even before it arrived!

And it is working great so far. Except for one issue…
Today I tried plugging in a stereo headset (tried several to be sure and an external headphone amplifier) and find the 2 channels of the stereo headphone jack on the SDS100 are wired out of phase.

Yes, the shaft of the 1/8” stereo plugs are fully seated in the jack and the shells of the connectors are not being blocked from fully seating by the way the jack is recessed from the top surface of the unit for the rubber flap.

Also, when plugged into my BCD160DN, all of these headphones receive a normal, in phase signal.

There’s an old RR forum thread about this that concluded the same but I’m not sure anyone has notified you guys about this.

In any case, this is really disappointing for such an expensive device.
Might there be a chance this can be fixed in software?
Or is it a physical design or production issue with the actual wiring to the jack or the headphone amp reversed?
If it is physical, I’ll have to build a short phase reversal cord when I want to use headphones with the SDS100. But I really shouldn’t have to 😊

Thank you in advance for routing this to the appropriate engineering team.

Best regards,

--Mark--

 

[AB5ID]

That's queer. 🤔

 

[Ubbe]

The earphone amp are a stereo device that used to run both channels in the same phase. I use a 2 ohm speaker to my SDS100E and the audio level increase if I run both channels to my speaker. The speaker amp runs in bridged mode, its two channels are in opposite phase, to deliver a higher output power. Maybe they now use the same IC for earphones as the speaker but it still runs in bridged mode. Let us know what Uniden answers.

/Ubbe

 

[MarkyM]

The earphone amp are a stereo device that used to run both channels in the same phase. I use a 2 ohm speaker to my SDS100E and the audio level increase if I run both channels to my speaker. The speaker amp runs in bridged mode, its two channels are in opposite phase, to deliver a higher output power. Maybe they now use the same IC for earphones as the speaker but it still runs in bridged mode. Let us know what Uniden answers.

/Ubbe

Will do. Nothing yet from them.

 

[MarkyM]

I just received a reply from Uniden Support (see below).
I am asking them if this will be a software fix or if hardware modification will be needed.

Thank you for reaching out and for your feedback.

We are aware of the issue and are planning to change this in the future.
Please let us know if you have any further questions or concerns.

Thank you,
Uniden Customer Support

--Mark--

 

[nessnet]

I just received a reply from Uniden Support (see below).
I am asking them if this will be a software fix or if hardware modification will be needed.

Thank you for reaching out and for your feedback.

We are aware of the issue and are planning to change this in the future.
Please let us know if you have any further questions or concerns.

Thank you,
Uniden Customer Support

--Mark--

I think you just had smoke blown up your keister....
(Hardware and it's doubtful they will change it)

 

[AB5ID]

I think you just had smoke blown up your keister....
(Hardware and it's doubtful they will change it)

Hopefully they can invert the audio of one channel before going from digital to analog, assuming the audio is digital in a 2 channel state.

 

[AB5ID]

I just received a reply from Uniden Support (see below).
I am asking them if this will be a software fix or if hardware modification will be needed.

Thank you for reaching out and for your feedback.

We are aware of the issue and are planning to change this in the future.
Please let us know if you have any further questions or concerns.

Thank you,
Uniden Customer Support

--Mark--

How'd you figure out the left and right were out of phase? Did you ears just pickup on it?

 

[lamarrsy]

How'd you figure out the left and right were out of phase? Did you ears just pickup on it?

180 degrees out of phase audio has an effect of like “pulling” the audio on one side or the other. It’s difficult to explain with words.

In my audio training course way back then when I was studio engineer, we trained ours ears on two speakers being connected 180 degrees out of phase: we placed ourselves in just the middle of the 2 speakers, and by just moving our torso just a bit right and left, we could hear the “pulling” (or “sucking”) effect toward right or left.

Once you’ve heard it, you can recognize it anywhere, including with earphones like MarkyM explained here above.

 

[Ubbe]

Hopefully they can invert the audio of one channel before going from digital to analog, assuming the audio is digital in a 2 channel state.

The audio are always digital from the receiver to the DSP in a SDS scanner. They would have to look at the scanners serial number, as they must know when they started using a phase shifting design, and also only phase shift back when the earphone are connected and not the speaker output. It takes 5 minutes for a coding guy to do that.

/Ubbe

 

[MarkyM]

Update...
I wrote back to Uniden Support asking them if they could provide an ETA for a fix and if the problem is hardware or if it might be able to be fixed in software:

Thank you for the reply.
Will this be a software fix?
Or will a hardware modification be required?
Can you provide an ETA?
Thanks again,

And they have just replied but seem a bit confused, asking me if I want to send my unit in for inspection. I replied back as follows below.
At this point, I think it would be very helpful if they received some more emails from other customers that can verify the problem.
You can reply here and I'll forward your comments or you can write to them directly at custsupport@uniden.com

Here's the thread with them as of today:

The way the jack is designed on the SDS100 should not cause audio to sound incorrect with a stereo headset.

I respectfully disagree. I don’t think this is a problem with my particular unit as it is brand new, just purchased from Scanner Master on March 14th, serial number xxxyzzzzzzzz. Also, there’s a thread on Radio Reference from back in 2018-2019 that confirmed that the headphone jack is indeed providing out of phase signal.

I am an experienced broadcast and audio engineer and I can tell you with 100% certainty that it is.
Not to mention your admission of same in your previous reply: We are aware of the issue and are planning to change this in the future.

And this may not be a hardware issue with the way the jack is wired. Maybe it is a software problem. Or an error in the DSP domain ie. signal routing through an FPGA or something.

If you would like for Uniden to inspect your scanner, our Support Team states that you should send your device to us for repair.

If you really want me to send my unit in, you will need to send me a loaner unit or swap mine with a new unit. But this should not be necessary as I would suspect that any unit will do this. Have you or an engineer actually tested a unit off the production line? Or any SDS100 unit? A simple test with a dual-channel oscilloscope would be able to prove this in a few minutes.

Or take a stereo headset and have an SDS100 and a BCD160DN handy. Tune both radios to the local NOAA weather channel and compare the sound between the two radios in the headphones. Or better yet, connect the SDS100 to an external stereo amplifier and set the amplifier to mono mode. The audio from the SDS100 should nearly disappear while the audio from the BCD160DN remains loud and clear. This is not rocket science guys! I can provide a video of me doing this test if you want.

I am fine for now as I have constructed a headphone adapter cable that takes the “tip” signal from the 3.5mm jack and feeds it to both headphone channels for a correct, in phase mono signal. The “ring” lead is left floating. This allows the headphones to sound perfectly normal instead of having that strange, hollow sound of a signal that is 180 degrees out of phase.

--Mark--

 

[MarkyM]

I asked Uniden support if it would be helpful to do a video that shows the problem.
They said to go ahead with that, which I did!
I have sent it to them and have also posted it here where you can watch it as well:

--Mark--

 

[MarkyM]

Uniden Support has received the video and has replied as follows:

Thank you for bringing this to our attention. Ive sent this video link to our QC department for exposure to this instance. While it is not something we commonly would test for during our QC process when it arrives to our facility in Texas, it is always worth looking into for both the customer experience, as well as keeping our assemblers to a necessary standard of the specifications we expect them to provide for our product(s).

At this time I don't have a solution for this issue, but we will be investigating this accordingly. I understand if this is upsetting by any means, but rest assured now that we have been made aware of it, it will be looked into over the coming weeks.

So let's see what they come up with.
Also, it couldn't hurt for more SDS100 owners to report this to:

custsupport@uniden.com