Differential Output

Correct. The purpose of a differential speaker output (often called bridge mode output) is to eliminate the need for electrolytic output capacitors when using a single-supply power source, and to double the available speaker voltage, thereby quadrupling the maximum power obtainable from the power source, which is often a small battery. A bridge output is fully differential, and has no knowledge of, nor need to interact with ground. Very small speaker amplifier ICs can be made using class-D (switchmode) H-bridge output stages, which dissipate little heat while driving the speaker. But it is necessary to incorporate four power MOSFETs into the IC for the speaker current.

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 Thanks,
    - Win

None.

Thank you all for your informative answers. The speaker is disconnectable (headphones via phonojack), but the initial center point offset should only induce a click or pop sound in the headphones. Since this is not a problem, I'll leave out the resistors.

Cheers, Chris

I don't understand your comment about center-point offset. In these balanced amplifiers, both outputs are at the same voltage with no signal, so the difference voltage is zero, and plugging in a headphone should not make a click. Note, the outer ring of the headphone jack shouldn't be grounded!

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 Thanks,
    - Win

Maybe the resistors are advisable if the loudspeaker can be disconnected. Not to provide a load on the amplifier but to prevent possible excessive centre-point offset.

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Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Apparatus wrote (in ) about 'Differential Output', on Sun, 12 Dec 2004:

Are you sure? There are two aspects:

1. The offset may damage the chip over time;
2. The click may exceed the 'acoustic shock' limits. People tend to put the headphones on and then plug them in. Since many headphones produce

100 dB SPL for 1 mW or less input, the possibility of getting more than 126 dB SPL (the ITU recommended limit) is significant. I have experienced a 126 dB click and I assure you it is VERY unpleasant.

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Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Winfield Hill wrote (in ) about 'Differential Output', on Sun, 12 Dec 2004:

Well, theoretically zero. What actually happens depends on the circuit configuration and the device characteristics.

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Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

"John Woodgate" schreef in bericht news: snipped-for-privacy@jmwa.demon.co.uk...

[snip]

Playing Russian Roulette can be worse .

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Thanks, Frank.
(remove 'q' and 'invalid' when replying by email)

I read in sci.electronics.design that Allan Herriman wrote (in ) about 'Differential Output', on Mon, 13 Dec 2004:

The 126 dB limit for clicks was applied in UK at the time of de- regulation, and I am not sure where it came from. The ITU document is P360, and I don't have a copy of it. The predecessor had 135 dB for very short clicks and 125 dB for longer disturbances.

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Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

John, which ITU recommendation is that?

Thanks.

Allan