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What's the real reason that laptop batteries are made not-accessible?

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ogden:

--- Quote from: magic on December 12, 2021, 11:00:35 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 :)

--- End quote ---

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

NiHaoMike:

--- Quote from: SilverSolder on December 11, 2021, 11:41:10 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.

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

SilverSolder:
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

David Hess:

--- Quote from: SilverSolder on December 11, 2021, 11:41:10 pm ---
--- Quote from: NiHaoMike on December 11, 2021, 11:20:28 pm ---
--- Quote from: SilverSolder on December 11, 2021, 10:50:21 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.
--- End quote ---

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

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.
--- End quote ---

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.


--- Quote from: NiHaoMike on December 12, 2021, 12:31:11 pm ---With sufficiently well matched resistors, the CMRR of a differential amplifier is more than good enough.
--- End quote ---

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.

SilverSolder:

--- Quote from: NiHaoMike on December 12, 2021, 12:31:11 pm ---
--- Quote from: SilverSolder on December 11, 2021, 11:41:10 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.

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

--- End quote ---

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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