General > General Technical Chat
What's the real reason that laptop batteries are made not-accessible?
<< < (40/43) > >>
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...
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod