Gp2x Audio

[WarmFluffyUK]

Since I got my fantastic GP2X I noticed there was something not quite right with the stereo separation. Sometimes in games it would appear to be louder in one channel and movies and music didn't quite sound right. And this morning it hit me, the speakers are out of phase. So I took the back off and correct it YAYYY.

And for those of you who have just shouted out "What the heck is the daft girl on about now?" I will tell you.

If you ever had an old hi fi that had a stereo wide switch on it, and wondered how it works? It's simple, it just swaps the polarity on one of the speakers. So when one speaker is pushing the other is pulling giving you an out of phase sort of spacial stereo signal.

All I did was, took the back off the GP2X, and unplugged one speaker and plugged it back in the wrong way round. Or in this instance, the right way round!!! Hey presto, I now get a correct stereo image!!!!

 

[sam fisher]

if the GP2x has the polarity of the speaker reversed. Then surely superposition of exactly opposite waves would be causing us to hear a massive degradation of image quality?

 

[craigix]

Sam, which uni are you planning to goto?

 

[WarmFluffyUK]

if the GP2x has the polarity of the speaker reversed. Then surely superposition of exactly opposite waves would be causing us to hear a massive degradation of image quality?

That's one way to put it, it just causes a sort of spacious effect. i.e. reverb will sound more prominent than vocals etc. Even mono signals will sound more spacious. Try it on your hifi by swapping the polarity on one of the speakers, and you will see what I mean.

This is why when you set up your sound system, you should always get the polarity of the speaker cables the correct way around, to prevent this kind of effect.

 

[sehs33]

ED already mentioned this few days ago, I will dig it up now, thanks for making a topic for this WarmFluffyUK.
edit: Here it is http://www.gp32x.de/board/index.php?showt...mp;#entry500092

 

[linoleum13]

Is this a common problem or is it jsut a mistake that was made on some units when they were made? I usually use headphones so I have never noticed a problem with the speakers. I guess the best way to figure it out is to try it...

 

[WarmFluffyUK]

ED already mentioned this few days ago, I will dig it up now, thanks for making a topic for this WarmFluffyUK.
edit: Here it is http://www.gp32x.de/board/index.php?showt...mp;#entry500092

Ah yes I see he mentioned it, The only difference between my resolve and Ed's is that I didn't need to solder anything. The speakers go to little white sockets on the board, you can unplug the one of them and plug it back in the wrong way. And this means all you have to do is to take the back off, no need to dismantle anything else .

 

[sam fisher]

Sam, which uni are you planning to goto?

What?

Also Fluffy:

If you were to position yourself in the exact centre between the two inversed sources, and there were no other variables to consider, the sounds would cancel out in your brain. Cool, huh?

 

[WarmFluffyUK]

Sam, which uni are you planning to goto?

What?

Also Fluffy:

If you were to position yourself in the exact centre between the two inversed sources, and there were no other variables to consider, the sounds would cancel out in your brain. Cool, huh?

You really do talk some rubbish now and then don't you :lol:

 

[sehs33]

I know that this is the case for electronic devices, but I was wondering if the GP2X warrenty terms does allows you to open it without voiding the warrenty? (I got mine from Play-asia in case warrenty terms are different from one distributor to the other).

 

[WarmFluffyUK]

I know that this is the case for electronic devices, but I was wondering if the GP2X warrenty terms does allows you to open it without voiding the warrenty? (I got mine from Play-asia in case warrenty terms are different from one distributor to the other).

I would assuming that taking the back off would void your waranty.

Anyway, here's a little pic of the GP2X with the back off pointing out the two speaker sockets:

 

[sam fisher]

Sam, which uni are you planning to goto?

What?

Also Fluffy:

If you were to position yourself in the exact centre between the two inversed sources, and there were no other variables to consider, the sounds would cancel out in your brain. Cool, huh?

You really do talk some rubbish now and then don't you :lol:

Its not rubbish, simple destructive superposition.

 

[WarmFluffyUK]

You really do talk some rubbish now and then don't you :lol:

Its not rubbish, simple destructive superposition.

You really do talk some rubbish now and then don't you :lol: - This could go on for hours :blink:

 

[sehs33]

Thanks for the image WarmFluffyUK, I want my unit's warrenty so am not trying this anytime soon, viva la headphones
BTW, why is ED's unit needed to be soldered? is it because he has a first edition? what is your unit? MK I/II ?

 

[WarmFluffyUK]

Thanks for the image WarmFluffyUK, I want my unit's warrenty so am not trying this anytime soon, viva la headphones
BTW, why is ED's unit needed to be soldered? is it because he has a first edition? what is your unit? MK I/II ?

I'm not sure how the Mk II differs internally from the Mk I, I guess when Ed comes online he may read this and answer that one himself

 

[EvilDragon]

ED already mentioned this few days ago, I will dig it up now, thanks for making a topic for this WarmFluffyUK.
edit: Here it is http://www.gp32x.de/board/index.php?showt...mp;#entry500092

Ah yes I see he mentioned it, The only difference between my resolve and Ed's is that I didn't need to solder anything. The speakers go to little white sockets on the board, you can unplug the one of them and plug it back in the wrong way. And this means all you have to do is to take the back off, no need to dismantle anything else .

It only needs soldering on an MK1
I didn't solder on my MK2, too Just turned the plug around.

However, not all gp2x have this problem, which is kinda weird.
And it still changes with my unit - so maybe some software also changes the phasing...?
Maybe some devkits do it this way and some others the other way.

 

[prairiefire]

I would assuming that taking the back off would void your waranty.

I would think you're correct too, but here's something I read in the manual when I had a problem with the switch that's built into the AC adapter jack (in case anyone was interested).

Anyways, in the User's Guide on GPH's website, under "Troubleshooting" (found by going to the "Product" tab, then on the left column, click on "Manual") you'll see:

"F. Joystick and buttons do not function properly.


Check if some foreign object is inside the system and if the problem persists or occurs too often, call the distributor you purchased GP2X from.
If you are playing MP3 files, this is usually because GP2X was set to power save mode to save battery power, You can switch this mode to normal mode by pressing select button.
No authorization for the analysis or modification of the system, or the analysis and use of its circuit configurations, is provided. Dissembling will void the system warranty."

Which begs the question, how can you check if some foreign object is inside the system if you can't disassemble it? (Note for a joystick or button problem due to a foreign object, you'll know that you have to remove the board from the case (to get at its front) since the case opens from the back.

 

[WarmFluffyUK]

I would assuming that taking the back off would void your waranty.

I would think you're correct too, but here's something I read in the manual when I had a problem with the switch that's built into the AC adapter jack (in case anyone was interested).

Anyways, in the User's Guide on GPH's website, under "Troubleshooting" (found by going to the "Product" tab, then on the left column, click on "Manual") you'll see:

"F. Joystick and buttons do not function properly.


Check if some foreign object is inside the system and if the problem persists or occurs too often, call the distributor you purchased GP2X from.
If you are playing MP3 files, this is usually because GP2X was set to power save mode to save battery power, You can switch this mode to normal mode by pressing select button.
No authorization for the analysis or modification of the system, or the analysis and use of its circuit configurations, is provided. Dissembling will void the system warranty."

Which begs the question, how can you check if some foreign object is inside the system if you can't disassemble it? (Note for a joystick or button problem due to a foreign object, you'll know that you have to remove the board from the case (to get at its front) since the case opens from the back.

That's like saying, you may not open the tin, but you may eat the chocolate within :lol:

Actually to be honest, I reckon the manual was badly translated. Some of the manuals I have seen in the past suffering from this are hilarious.

 

[notaz]

And I wondered why the unit had 2 speakers, but I could hardly hear stereo. After the change now I finally can!

The only problem left is that annoying channel (and phase, maybe?) switching. It happens nearly everywhere, including PD, it is most annoying in mp3 players. I suspect a bug in ac97 kernel driver or somewhere else in Linux.

 

[WarmFluffyUK]

And I wondered why the unit had 2 speakers, but I could hardly hear stereo. After the change now I finally can!

The only problem left is that annoying channel (and phase, maybe?) switching. It happens nearly everywhere, including PD, it is most annoying in mp3 players. I suspect a bug in ac97 kernel driver or somewhere else in Linux.

I don't think AC97 has anything to do with it as it will only output what is sent to it. The output stage on some units obviously are wired incorrectly.
Maybe we should make a pole, but I think most people who post on the pole will have no idea what they are voting for. I have noticed during my time on the planet that most people do not have the foggiest about what they actually hear. I mean if I said "Too much compression is being applied to today's music, it's ruining original music" Would you have any idea what the heck I was on about? Probably not... Mr Axe would

Audio is a very big grey area for most people, unless like me you have very good perception to it. Wy boyfriend is even more finicky than me... I am pitch perfect, but Phil's hearing is way more sensitive than mine...

I noticed problems instantly, but only realised the solution the oher day. I should have realised it earlier with my experience in audio etc....