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sinusoidal 2nd October 2007 08:35 AM

Can audio amplifiers reproduce pulse wave?
Hello, this is my first post :angel: The answer to the title of this post maybe "of course" but I'd like to pose this question.

Can a pulse wave, basically a square wave that does not have its upper or lower half i.e. a DC wave, be reproduced with reasonable fidelity by one of those popular Japanese receivers?

Handling a negative DC pulse wave that does not have positive half will be no problem too?

Also, will it have any ill effect on amplifier when continuously putting out series of high frequency pulses? (such as 18000 pulses a sec?)

Lastly, What sound editor software is good for creating/editing pulse wave (and save in pcm/wav format)?

Would appreciate your expert advice.

ilimzn 2nd October 2007 09:58 AM

In theory, the answer is yes, but in practise, all audio amplification chains block DC because it does not appear in audio, and in the event it does, it is considered an error condition. You could, however, construct an audio amp that does not do this by removing AC coupling components and of course making sure the topology is sound and stable for your purpose.

Amongst othe things, you should make sure your pulse still looks like a pulse once it goes through the amp. A rectangular pulse at 18000Hz is not going to be nearly rectangular when passed through a system that has it's bandwidth limited to 20-24kHz, which is the usual case with producing wav files. Even using 192kHz sampling rate (for which you need some serious hardware), what you would see on the output would be very unlike the intended pulse. Again, a custom-made DAC with no oversampling, digital filtering and putput filtering save something called a 'zero order hold' could be made, but questions remain on skills, cost and time involved.

Finally, assuming you do make it, in order to make pulses approaching square at 18000Hz, the bandwidth of the amp has to be amny times that, perhaps 10 times. If your pulses also have a low duty cycle (are narrow), it may be much more than 10 times. Depending on what output voltages and currents you require, this may be a very demanding circuit, design and implementation-wise.

jan.didden 2nd October 2007 02:33 PM

Agree with the above.
If you want to see what you can expect, look at some of the equipment tests of the magazines like Stereophile. They often test power amps with 10kHz square waves.

Jan Didden

Eva 2nd October 2007 02:59 PM

You don't really need an audio amplifier to produce a single-ended 18Khz square wave. There are simpler ways involving a regulated supply and a pair of switching MOSFETs.

PMA 2nd October 2007 04:49 PM

Amplifier can do it quite well, but loudspeaker not ;)

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