dc to speakers
- Thread starter nandac
- Start date
Audiodoc
Well-Known Member
Normally the current sent to the speaker is an alternating current which is basically an amplified analog audio signal. DC has a constant amplitude which overheats and destroys the voice coil of the speaker drivers hence it should be minimal at the output of the amplifier typically < 100mV. If this DC offset is high either due to absence of a capacitor at the amplifier input or an error in the amplifier circuit one can easily roast their speakers so one should ideally use protection circuits.
Last edited:
tirthankar
Active Member
One thing I'll like to add here..one of the primary cases when amps send dc to speakers is when they are overdriven. Amps have a specific power capacity. If driven too hard(at too high a volume) they can clip.
Any amplification set has two parts, a preamp has variable gain for volume control, and a power amp with a fixed high gain. They may be separate, or in a single chassis, as in an integrated. Power amps have a specific sensitivity, ie an input voltage at which they supply maximum power. If supplied with a higher voltage than that, the amp is overdriven.. it is asked to supply higher power than it can. As it tries doing that, the output ac waveform has its amplitude clipped by the lower powered output stage, ie, the peaks and crests become flattened slightly till the rated amplitude. This is a dc offset, which, if too high, can fry speaker tweeters.
High input voltage is caused when the volume control is turned too high, ie, preamp is supplying more than the power amp can handle
Morale- if one wants loud party sound, get efficient speakers or high powered amps. Else tweeters can be history.
Any amplification set has two parts, a preamp has variable gain for volume control, and a power amp with a fixed high gain. They may be separate, or in a single chassis, as in an integrated. Power amps have a specific sensitivity, ie an input voltage at which they supply maximum power. If supplied with a higher voltage than that, the amp is overdriven.. it is asked to supply higher power than it can. As it tries doing that, the output ac waveform has its amplitude clipped by the lower powered output stage, ie, the peaks and crests become flattened slightly till the rated amplitude. This is a dc offset, which, if too high, can fry speaker tweeters.
High input voltage is caused when the volume control is turned too high, ie, preamp is supplying more than the power amp can handle
Morale- if one wants loud party sound, get efficient speakers or high powered amps. Else tweeters can be history.
To add, an inductor (i.e. voice coil) offers zero impedance to DC, basically a short circuit. Hence even a very short duration of dc (a few seconds) into speakers will result in overheating and burning of the voice coil. It is much worse than clipping -- which usually has several zero crossings per second. I read in headfi.org that some badly designed amps have DC in their o/p which is devastating for the speakers/headphones.
On the other hand a series capacitor acts as open circuit to DC.
On the other hand a series capacitor acts as open circuit to DC.
anm
Well-Known Member
current sent to speakers is not exactly AC I think. AC is single frequency 50 Hz sine wave. Music signal would be more complex, and will have a range of frequencies.
But DC is bad because it will push the speaker but not pull back. So the energy would have no other way then to convert to heat, resulting in burning of driver.
But DC is bad because it will push the speaker but not pull back. So the energy would have no other way then to convert to heat, resulting in burning of driver.
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