Author Topic: What's the real reason that laptop batteries are made not-accessible?  (Read 22476 times)

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Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #175 on: December 11, 2021, 03:47:56 pm »
What's a "quack DAC" and who thinks it is more important than what buffer is used to actually drive the headphone load? ;)

"quack DAC" lol!  :D   I'm guessing it's 4 DACs in parallel.  Maybe you can get better accuracy that way, I don't know! Probably mostly audiophoolery.  Agreed about the output amp/buffer being more important....

[Edit:  Quad DAC is essentially a marketing name for an ESS brand DAC/Amp chip. It features a 32bit 384 kHz "quad" DAC stage, which is obviously way overspecced for audio frequencies. ]

My criteria for a smartphone are:
1) Must have SD card slot for big FLAC music collection.
2) Must have replaceable battery, and must have availability of extra large capacity batteries!
3) Must have headphone jack to drive headsets and classic car AUX inputs.  Bonus for higher quality audio circuitry!

As a result of this thread I've been looking at what's avaliable,  I've ended up ordering a V20 to have a closer look at - on paper, I like it a lot for my use case! 

The Galaxy Xcover comes close, but because nobody makes extended size batteries for it (yet, at least) it isn't ideal for me.  I'm guessing that this model will catch on eventually, it is probably still a little too new to have developed a supporting ecosystem of extended batteries!
« Last Edit: December 11, 2021, 04:01:36 pm by SilverSolder »
 

Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #176 on: December 11, 2021, 03:49:15 pm »
And then there's the fact that the girls like wired headphones, so who's the loser now? :D   
USB is wired, no problems there. I think it's mainly gamer girls who prefer wired since Bluetooth has higher latency.

If you look at the article in the link, it appears to be the "It-girls" that find the wires satisfyingly bohemian!  :D
 

Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #177 on: December 11, 2021, 03:57:54 pm »
If the benefits outweigh the disadvantages for you, fine. But you have to accept that not everyone comes to the same conclusion!

Sure. That's why we have endless list of different shopping choices. BTW I prefer function to fashion/religion and use what is best for occasion. When sitting @computer - I will be using decent wired over-ear headphones. As soon as I expect myself moving, I do not put studio headphones in my pocket, but rather BT earbuds. Charging is not an issue either - because earbud case can receive charging wirelessly from phone back-to-back.

I do the same thing,  except I do carry (smaller) over-ear headphones on the go too, because I find earbuds intensely uncomfortable.   I also have two older cars with AUX inputs.  One of them does support Bluetooth, SD cards, etc., but the sound quality of the AUX input is significantly better (when sourcing from a quality external FLAC player).  I have high hopes for the LG v20, let's see how that works out!
 

Offline PlainName

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #178 on: December 11, 2021, 04:10:34 pm »
Quote
because earbud case can receive charging wirelessly from phone back-to-back

Don't know if I think that is good or bad - on the one hand, as you say, you always have charged earphones, but on the other phone battery life can be an issue without some external thing draining it on the sly.
 

Online magic

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #179 on: December 11, 2021, 04:37:24 pm »
There is a public datasheet of this DAC :o
https://www.esstech.com/products-overview/digital-to-analog-converters/low-power-dacs-and-socs-to-headphone-socs/

Built-in headphone amplifier, voltnuts wouldn't approve. No specs at loading less than 300Ω.
No explanation of Quad DAC technology, but it's "acclaimed" :)
 

Offline NiHaoMike

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #180 on: December 11, 2021, 05:11:36 pm »
If you look at the article in the link, it appears to be the "It-girls" that find the wires satisfyingly bohemian!  :D
Thinking about that some more, I guess it would make sense for IT girls to want something that "just works" when they're used to working on stuff that keeps refusing to work.
Don't know if I think that is good or bad - on the one hand, as you say, you always have charged earphones, but on the other phone battery life can be an issue without some external thing draining it on the sly.
Turn that around, make the case bigger and have it double as an external battery for the phone.
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Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #181 on: December 11, 2021, 05:11:42 pm »
There is a public datasheet of this DAC :o
https://www.esstech.com/products-overview/digital-to-analog-converters/low-power-dacs-and-socs-to-headphone-socs/

Built-in headphone amplifier, voltnuts wouldn't approve. No specs at loading less than 300Ω.
No explanation of Quad DAC technology, but it's "acclaimed" :)


Interesting, thanks for linking!  - looks like the chip has its own built-in charge pump to generate the positive and negative supplies for the output amplifiers, I was wondering how they would do that...

The data sheet does say -106dB THD+N, 300mV RMS into 32 ohms.  Seems respectable enough?  Definitely comparable to my stand-alone FLAC player...




 

Offline PlainName

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #182 on: December 11, 2021, 05:22:59 pm »
Quote
make the case bigger and have it double as an external battery for the phone

I think it's already been tried.

1346993-0
 

Online magic

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #183 on: December 11, 2021, 05:35:53 pm »
Interesting, thanks for linking!  - looks like the chip has its own built-in charge pump to generate the positive and negative supplies for the output amplifiers, I was wondering how they would do that...

The data sheet does say -106dB THD+N, 300mV RMS into 32 ohms.  Seems respectable enough?  Definitely comparable to my stand-alone FLAC player...
LOL, I went straight to "analog characteristics" and completely missed the specs on the first page.
Yes, that's within the usually accepted "good enough for audio" limits, but hardly state of the art performance and you don't need friggin' 32 bits for that.
This output level is some 110+ dB SPL with typical IEMs, but less efficient headphones might require more.

I have seen the charge pump trick before. I think they do it because:
- it doubles the output swing without differential drive, which is impossible with 3-terminal headphones
- the charge pump runs at high frequency so it gets away with smaller (and crappier) capacitors than those required for AC coupling the load
 

Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #184 on: December 11, 2021, 09:38:42 pm »
Interesting, thanks for linking!  - looks like the chip has its own built-in charge pump to generate the positive and negative supplies for the output amplifiers, I was wondering how they would do that...

The data sheet does say -106dB THD+N, 300mV RMS into 32 ohms.  Seems respectable enough?  Definitely comparable to my stand-alone FLAC player...
LOL, I went straight to "analog characteristics" and completely missed the specs on the first page.
Yes, that's within the usually accepted "good enough for audio" limits, but hardly state of the art performance and you don't need friggin' 32 bits for that.
This output level is some 110+ dB SPL with typical IEMs, but less efficient headphones might require more.

I have seen the charge pump trick before. I think they do it because:
- it doubles the output swing without differential drive, which is impossible with 3-terminal headphones
- the charge pump runs at high frequency so it gets away with smaller (and crappier) capacitors than those required for AC coupling the load

Yes, audio specs are often of the "if somethin's worth doing, it's worth OVERdoing" type!   


 

Offline IanB

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #185 on: December 11, 2021, 10:02:42 pm »
Yes, audio specs are often of the "if somethin's worth doing, it's worth OVERdoing" type!

Indeed. I'm a bit confused about the balanced 2.5 mm headphone connector. Apparently, balanced connections are good for improved noise rejection, but is there ever an issue with noise on a headphone cable?
 

Offline NiHaoMike

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #186 on: December 11, 2021, 10:31:36 pm »
Indeed. I'm a bit confused about the balanced 2.5 mm headphone connector. Apparently, balanced connections are good for improved noise rejection, but is there ever an issue with noise on a headphone cable?
Rarely an issue for headphones, but for amplifiers it's a big problem especially if the source device is connected to the noisy power ground. Apparently, automotive amplifiers have solved that issue by using differential amplifiers for the 3.5mm inputs. Not as good as a proper differential link, but automotive has been an acoustically noisy environment so it was good enough. EVs have changed that - in slow traffic or stopped at a light, they're nearly silent. Newer car radios have USB ports which finally provided a digital input as well as improve integration with portable devices. Or just use a USB drive for music - why waste expensive storage where cheap storage is plenty good enough?
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Online magic

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #187 on: December 11, 2021, 10:34:55 pm »
Dunno, go ask on head-fi :-DD :popcorn:

Realistically,
- you gain some fractional stereo separation (no shared ground return), probably irrelevant due to the resistances involved
- you get to use different upstream gear - possibly the biggest difference which actually exists
 

Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #188 on: December 11, 2021, 10:44:12 pm »
Yes, audio specs are often of the "if somethin's worth doing, it's worth OVERdoing" type!

Indeed. I'm a bit confused about the balanced 2.5 mm headphone connector. Apparently, balanced connections are good for improved noise rejection, but is there ever an issue with noise on a headphone cable?

Theoretically, if one channel is playing very loud and the other is dead silent, you could get some cross talk from one earbud to the other if the cable has a common ground and significant resistance?

Googling returned an apparent yes:  https://www.soundonsound.com/sound-advice/q-it-normal-get-crosstalk-appearing-headphones 

But the problem becomes negligible if four wires are used, so the two "ears" do not share a common return cable.

In other words, this is a non-issue with decent headphones...   looks like more audiophoolery, to some extent.
 

Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #189 on: December 11, 2021, 10:50:21 pm »
Indeed. I'm a bit confused about the balanced 2.5 mm headphone connector. Apparently, balanced connections are good for improved noise rejection, but is there ever an issue with noise on a headphone cable?
Rarely an issue for headphones, but for amplifiers it's a big problem especially if the source device is connected to the noisy power ground. Apparently, automotive amplifiers have solved that issue by using differential amplifiers for the 3.5mm inputs. Not as good as a proper differential link, but automotive has been an acoustically noisy environment so it was good enough. EVs have changed that - in slow traffic or stopped at a light, they're nearly silent. Newer car radios have USB ports which finally provided a digital input as well as improve integration with portable devices. Or just use a USB drive for music - why waste expensive storage where cheap storage is plenty good enough?

A good hack for circumventing this problem in a car is to use an audio signal tranformer to galvanically isolate the signal between the source and the destination device.  Miracle cure, in many cases.
 

Offline NiHaoMike

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #190 on: December 11, 2021, 11:20:28 pm »
A good hack for circumventing this problem in a car is to use an audio signal tranformer to galvanically isolate the signal between the source and the destination device.  Miracle cure, in many cases.
Opamps and a few well matched resistors are a lot cheaper than a decent audio transformer.
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Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #191 on: December 11, 2021, 11:41:10 pm »
A good hack for circumventing this problem in a car is to use an audio signal tranformer to galvanically isolate the signal between the source and the destination device.  Miracle cure, in many cases.
Opamps and a few well matched resistors are a lot cheaper than a decent audio transformer.

Does that solve ground loop issues though? Other than using optical coupling of some kind, I can't think of an alternative to a transformer for that.
 

Offline ogden

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #192 on: December 12, 2021, 05:28:47 am »
Indeed. I'm a bit confused about the balanced 2.5 mm headphone connector. Apparently, balanced connections are good for improved noise rejection, but is there ever an issue with noise on a headphone cable?
Rarely an issue for headphones, but for amplifiers it's a big problem especially if the source device is connected to the noisy power ground.

Right. It gives better price/SNR, option to use unipolar supply with push-pull amp on the output - especially good for portable players. Also 2.5mm/4.4mm balanced output is compatible to balanced XLR inputs of hi-end audio gear.

 

Offline ogden

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #193 on: December 12, 2021, 09:51:31 am »
No explanation of Quad DAC technology, but it's "acclaimed" :)

I wonder - maybe quad DAC is about using two stereo DAC's, one for each channel - to get better separation between channels?  :-//
 

Online magic

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #194 on: December 12, 2021, 11:00:35 am »
Apparently something like that.
https://www.esstech.com/ess-technology-brings-advanced-audiophile-features-to-mobile-devices-for-the-first-time/
Quote
QUAD DAC Technology – Internally connected parallel quad DACs deliver superb 124dB DNR and -112dB THD+N.

Fun fact: whenever there is an integrated amplifier in something, they point out how it is capable of driving "professional high impedance headphones" but don't mention "consumer low impedance headphones" too much :)
 

Offline ogden

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #195 on: December 12, 2021, 11:34:01 am »
Fun fact: whenever there is an integrated amplifier in something, they point out how it is capable of driving "professional high impedance headphones" but don't mention "consumer low impedance headphones" too much :)

High impedance pro headphones need much higher output level to achieve specified sound pressure level. Owners of low impedance consumer stuff most likely don't care - their headphones are overdriven or not :D
 

Offline NiHaoMike

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #196 on: December 12, 2021, 12:31:11 pm »
Does that solve ground loop issues though? Other than using optical coupling of some kind, I can't think of an alternative to a transformer for that.
With sufficiently well matched resistors, the CMRR of a differential amplifier is more than good enough.
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Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #197 on: December 12, 2021, 02:00:49 pm »
It will be interesting to see how this chip/phone compares to a dedicated audio player.  I'd be surprised if it comes close to Wolfson WM8740 DACs coupled with a good external amp - but it has a chance of being quite decent! :D
« Last Edit: December 12, 2021, 02:02:20 pm by SilverSolder »
 

Offline David Hess

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #198 on: December 12, 2021, 08:19:39 pm »
A good hack for circumventing this problem in a car is to use an audio signal tranformer to galvanically isolate the signal between the source and the destination device.  Miracle cure, in many cases.

Opamps and a few well matched resistors are a lot cheaper than a decent audio transformer.

Does that solve ground loop issues though? Other than using optical coupling of some kind, I can't think of an alternative to a transformer for that.

It is not galvanically isolated like a transformer or optical coupling is, but a difference or instrumentation amplifier does remove the ground loop.  I have done it this way many times.

With sufficiently well matched resistors, the CMRR of a differential amplifier is more than good enough.

Just 1% resistors for a worse case common mode rejection of 34 dB is usually good enough.  Only a moderate amount of common mode rejection is required in most cases to make a huge difference.
 

Offline SilverSolder

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Re: What's the real reason that laptop batteries are made not-accessible?
« Reply #199 on: December 12, 2021, 08:49:43 pm »
Does that solve ground loop issues though? Other than using optical coupling of some kind, I can't think of an alternative to a transformer for that.
With sufficiently well matched resistors, the CMRR of a differential amplifier is more than good enough.

I will definitely try that (thanks @David Hess as well). 

The audio transformers sold for this purpose on Amazon did not measure well...   to put it mildly! :D    It shouldn't be hard to make an op amp work better than that...
 


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