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Audio: Headphone “Anti thump” delayed output rev 1.1

Posted on Monday, August 11th, 2014 in hacks by DP

anti thump 1.1 PCB render

Rupert Hirst writes:

A long awaited refresh, to my previous “Anti Thump” headphone output delay circuit, designed back in 2011.
The Idea behind the circuit is to introduce a small delay, during initial power up, to electrically isolate and protect equipment connected directly to an amplifier. Often, during power up, amplifiers can produce an audible thump, through speakers or headphones. This can lead to damage of the connected equipment over time.
Thumps and clicks will occur when the supply rails voltages are too low to allow the amplifier to control its output voltage.
As the circuit has an immediate disconnect when powered off, most instances of turn off thump are also dealt with, such as output capacitor discharges.

This entry was posted on Monday, August 11th, 2014 at 9:00 pm and is filed under hacks. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

8 Responses to “Audio: Headphone “Anti thump” delayed output rev 1.1”

  1. KH says:

    Thumps can damage speakers or headphones? I don’t believe it one bit. Can anyone point to some kind of relevant manufacturer’s app note? (Forum anecdotes don’t count, most rely on the ear and the brain, and that system is *very* adaptive.) Plenty of audio amplifier ICs suppress pops and clicks, but all datasheets I’ve seen imply these are a cosmetic issue. Prove me wrong.

  2. TK says:

    @KH it is not really the blip, many headphone amplifiers have DC voltage offset and voltage fluxions issues the first few seconds to a minute of being powered. DC voltage offset is the big thing to avoid as it is useless energy that causes heat to build up in the coils of the headphones. DC blocking caps don’t always do the job, and not all amps are equal.

  3. TK says:

    @KH it is not really the blip, many headphone amplifiers have DC voltage offset and voltage fluctuations issues the first few seconds to a minute of being powered. DC voltage offset is the big thing to avoid as it is useless energy that causes heat to build up in the coils of the headphones. DC blocking caps don’t always do the job, and not all amps are equal.

  4. TK says:

    @KH it is not really the blip, many headphone amplifiers have DC voltage offset and voltage fluctuations issues the first few seconds to a minute of being powered. DC voltage offset is the big thing to avoid as it is useless energy that causes heat to build up in the coils of the headphones. DC blocking caps don’t always do the job, and not all amps are equal.
    Thumps, or loud blips depending on level may damage headphones (especially cheap one, quality expensive ones are more resistant). Also I would note not all IC or op-amps are made equal, some are better than others depending on design and cost. Typically these circuits are needed on amps which have tubes, or discrete (transistor based) op-amp output stages, or power amp chips (common place in stereo and av receivers).

    • KH says:

      I see a lot of anecdotal talk, but no actual data. People in forums warning newbies about such-and-such, but nobody has first-hand killed headphones or have numbers of killed headphones, or damaged amplifiers or what not. People with ideas about their headphones having changed characteristics, listening by ear only. Plenty of people with supposed wise opinions or tips, but what is real and what isn’t? A witch doctor can say the same things about his or her methods with complete conviction too whilst believing in the stuff themselves. And they would all be sincere too.

      I would be very much obliged if anyone can find an app note or a datasheet from any kind of manufacturer that talks about this, or any sort of real data.

      • jake says:

        Why do you need to see an app note or datasheet, to believe it is not snake oil. I think we can agree it is undesirable however you see it.

      • KH says:

        Some actual data, any actual data, otherwise we may be doing things for the wrong reasons and we’re dabbling in BS. Are we any better than peddlers selling ridiculous cables at a premium then? Sure, if you are a hobbyist, this may be no big deal, but in some fields of engineering, this kind of attitude can eventually get people killed. Is there no one here with engineering training? Accepting this too easily is like being happy with a $1000 luxury watch that has a factory price of $100 from China.

        I would *love* to see something more substantial on this issue.

  5. TO says:

    I unfortunately do not have data either way, but I do appreciate your approach KH.

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