SDS100/SDS200: Bug fix? Headphone audio out of phase?

[W5ATX]

Saw a video on youtube and confirmed it on mine as well. I purchased a pair of powered computer speakers and when i plug them in to the sds100, the audio is out of phase in one channel. if i take one speaker of the pair and lay it face down or turn it 180 degrees (facing opposite of the other speaker) then it sounds wonderful! any way to change this in the menu or future firmware update? perhaps a stereo to mono adapter is in order? i remember upman saying to always plug a stereo plug into the headphone jack, something about a mono plug shorts it out. thanks in advance.

 

[prcguy]

Does one "main" speaker have the computer cable and all the adjustments and the other speaker simply plugs into the main, or something else? If its a main speaker with all the controls and amplifier and the other speaker is passive and it plugs into the main, that would be the one to open up and reverse the wires right at the internal speaker. If its something else you will have to describe it.

Traditionally, a speaker that is wired correctly will push the speaker outward when you connect a 1.5v battery + to the speaker + and minus to minus. You can't do that with an amplified speaker so you have to use an audio oscillator and oscilloscope, or just make sure both speakers are in phase by sending a mono signal to both and listen between them for normal sound like you probably did with your scanner. If one speaker is reversed it will sound like the music or whatever is being sucked out of the air.

 

[W5ATX]

Thanks for the reply, there's the main speaker with the wall wart power input and 1/8" stereo speaker input, the other speaker is hard wired into the primary speaker, i've seen some that plug in. i may open the secondary speaker and reverse the leads on the driver. i've also tried this with another set of speakers, and also my headphones. all have the same out of phase sounding results. when i lift one side of the headphones off my ear the audio sounds fine, when they are both on, it sounds like it's 180 degrees out of phase., the bass disappears. wondering if this is intentional in the sds100 or if there's a way to fix it in the menu or via firmware update.

 

[RFI-EMI-GUY]

Sounds like a bug, not a feature...

 

[Ubbe]

It's a mechanical phenomen. There's no scanner that outputs stereo sound but modern Uniden scanners use a speaker amplifier that have floating, push pull, outputs. On older scanners one speaker terminal are grounded and the other one are coupled thru a capacitor to the amplifier that has a DC output of half the battery power. To get more watts into a speaker so it can be used in a vehicle you use an amplifier that has the grounded speaker terminal connected to a second amplifier stage that delivers the audio 180 degree out of phase. When one speaker terminal goes positive the other goes negativ. It will quadruple the output power to the speaker.

The speaker connector, and the headphone connector, are of a stereo type that have the two audio signals at the tip and the ring and if a one speaker are connected there it will sound ok. But if you connect one speaker to tip and sleeve and another one to ring a sleeve, as all stereo active speaker pairs are configured, they will sound out of phase to each other.

/Ubbe

 

[jonwienke]

The speaker connector, and the headphone connector, are of a stereo type that have the two audio signals at the tip and the ring and if a one speaker are connected there it will sound ok. But if you connect one speaker to tip and sleeve and another one to ring a sleeve, as all stereo active speaker pairs are configured, they will sound out of phase to each other.

This is 100% wrong. Uniden scanners send the same audio, in phase, to both stereo channels. The same signal voltage is sent to the tip and ring, so that you get the exact same signal in both ears of stereo earbuds or headphones. Your computer speakers are miswired, or your computer is inverting one of the channels for some reason, like a driver bug.

Also, if you aren't using a ground loop isolator between the SDS100 and the computer, you're shorting out one side of the audio, and will hear noise and artifacts in the audio on the computer. Unplug the USB cable from the scanner so it is running on battery power, and see if the problem goes away.

 

[W5ATX]

so how are my ears, my friends ears, and the inverted waveform shown on audacity wrong? all i can say is plug a single speaker in and compare it to a pair of stereo speakers, the audio is completely different. the audio is messed up on both sds100's with any set of stereo computer speakers i plug in. when i plug the same stereo speakers into my other scanners, my cell phone, my ham radio, etc everything is fine.

so to solve the problem, i opened one side of my logitech computer speakers and reversed the polarity on the speaker and problem solved.

 

[jonwienke]

Sounds like your 1/8 plug isn't seating in the SDS100 correctly, and scanner ground is connecting to cable ring, and scanner ring is connecting to the cable tip. That would invert the channel connected to ring. The plug is probably too big to fit in the SDS100 headphone jack recess properly.

Use a different cable with a smaller diameter plug, and I'll bet the issue goes away.

 

[jonwienke]

If the body of the 1/8 plug is larger than 8.5mm/.340", it will not fit all the way into the headphone jack recess on the SDS100, and you'll have the connection mismatch problem I described and get an inverted channel.

 

[prcguy]

Most of the barrel shaft on an 1/8" or similar stereo plug is ground or common so I think it would be difficult to insert one where you would get inverted audio in one channel. I've seen some consumer gear that was wired out of phase by accident and most people would never know it listening to computer speakers in stereo. The bass might be a little low and the frequency response will be off and its when you listen to mono and both speakers are equally spaced around you that it will be obvious something is wrong.

A proper mating plug and a dual trace oscilloscope and a service monitor generating a signal with an audio tone will tell you if the SDS100 is actually inverted on one channel.

If the body of the 1/8 plug is larger than 8.5mm/.340", it will not fit all the way into the headphone jack recess on the SDS100, and you'll have the connection mismatch problem I described and get an inverted channel.

 

[jonwienke]

Also, in a push-pull audio configuration, if the push and pull were wired to tip and ring rather than pull wired to ground and push wired to both tip and ring, ground loops wouldn't be an issue. The audio signal would be balanced above and below ground, and grounding ground wouldn't be an issue.

 

[KE5MC]

...snip...
all i can say is plug a single speaker in and compare it to a pair of stereo speakers, the audio is completely different.
...snip...

so to solve the problem, i opened one side of my logitech computer speakers and reversed the polarity on the speaker and problem solved.

If the single speaker you plug in has a mono 1/8" plug, then yes the audio is messed up. The sleeve of the plug is extending into the area of the ring and shorting that signal to the common sleeve. Likely the single source audio in the radio is connected thru isolation resistors to the tip and ring contacts of the socket otherwise no audio at all.

I believe the single source audio out of the SDS100 makes it easier to identify a phasing error in a stereo system as the signal is the same on both left and right channels. The typical phasing checks I have done on stereo system forces me to pay closer attention because of the true stereo difference at the input. As I recall the bass is the area to focus on for phasing which many computer audio systems lack. Reversing the polarity at the speaker is for me a 'slam dunk' the factory didn't get it right. I'm betting music could actually be sounding better now.

 

[jonwienke]

Likely the single source audio in the radio is connected thru isolation resistors to the tip and ring contacts of the socket otherwise no audio at all.

Yes, that is the case to limit headphone volume, which makes the likelihood that the tip and ring are wired out of phase practically nil.

 

[prcguy]

Things that are mixed to center in a stereo recording are affected most when phase is reversed. Bass is typically center and also most vocals.

Is the SDS100 advertised as providing FM stereo audio to the earphone jack or is it known to have only one audio channel split to a stereo plug? If its actually stereo then the audio amp(s) are probably wired ok in the receiver and the DSP could be programmed wrong and providing out of phase audio to the amps downstream.

If the single speaker you plug in has a mono 1/8" plug, then yes the audio is messed up. The sleeve of the plug is extending into the area of the ring and shorting that signal to the common sleeve. Likely the single source audio in the radio is connected thru isolation resistors to the tip and ring contacts of the socket otherwise no audio at all.

I believe the single source audio out of the SDS100 makes it easier to identify a phasing error in a stereo system as the signal is the same on both left and right channels. The typical phasing checks I have done on stereo system forces me to pay closer attention because of the true stereo difference at the input. As I recall the bass is the area to focus on for phasing which many computer audio systems lack. Reversing the polarity at the speaker is for me a 'slam dunk' the factory didn't get it right. I'm betting music could actually be sounding better now.

 

[jonwienke]

Is the SDS100 advertised as providing FM stereo audio to the earphone jack or is it known to have only one audio channel split to a stereo plug?

There's only one audio output, sent to both channels. I can replicate the problem by pulling a properly-fitting 1/8" stereo headphone plug partway out of the SDS100 headphone jack. The volume drops off dramatically, and the bass goes away when the headphone plug ground floats, and the ring-ground audio output is connected to tip-ring on the plug.

 

[jonwienke]

Here's a photo:


Note that the distance the plug is backed out of the jack is approximately the height of the recess that mates with the jack cover seal. I guarantee that's what the OP's problem is, and he's getting lower volume than normal because one jack output is connected to both plug outputs in series, rather than both jack outputs being connected to both plug outputs in parallel.

 

[W5ATX]

it's not the plug. here's the video on youtube. you can see the waveform is 180 degrees, what's interesting is when he splits the stereo signal it to dual mono there's an improvement, but the real improvement is when you listen to either the left or right channel by itself.

youtube.com/watch?v=5iBQ0wQuCyM

 

[jonwienke]

Curious how you "know" that when the video never shows the scanner or the cable plugged into it. As I said, when I plug in headphones with a plug that fits properly, there is no channel phase inversion until I pull the plug out partway as shown in the photo. My scanner is #541 of the first batch of SDS100s made (it came with the small battery, too), so if there was a hardware problem, it would have it.

What the video shows is exactly what I hear when I pull the plug out partway though. With the plug fully seated, no phase inversion, audio sounds correct. With the plug pulled out partway as shown, phase inversion, tinny audio, etc., just like in the video.

 

[tvengr]

The tip and ring audio outputs are definitely 180 degrees out of phase. I just injected a signal into my SDS100 from a signal generator modulated by a 1 KHz tone. Using a dual trace scope, I saw that the signals are out of phase. That is what is known as a balanced audio output. Professional audio equipment always uses balanced inputs and outputs because there is less susceptibility to picking hum and noise, especially on long audio runs. Any magnetic field cutting through the cable would induce the same in phase signal on both wires which would result in a cancellation at a balanced audio input. I also verified that it is a balanced output by feeding the audio to the balanced input of an audio mixer. If the tip and ring audio were in phase, the audio would be cancelled out, resulting in extremely low level and very poor low frequency response. The SDS100 works perfectly with the mixer.

 

[jonwienke]

What serial number is your SDS100?