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.

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!

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.

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

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.

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

Playing Russian Roulette can be worse .

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.

John, which ITU recommendation is that?

Thanks.

Allan