On 21 Jan 2005 01:06:15 GMT, Codifus wrote:

DOA wrote:
When I don't have anything playing and just a bit of volume I can hear
a hiss from my speakers. But thats only if i put my ear up to it(2
inches away). But its more evident if I have the volume up to max. Then
I can hear it. Its not extrememly loud but its there. Is that normal on
all speakers? Or do I need to get better connectors for the speaker
wire? Now to reiterate I don't have anything playing. just turining the
volume knob. What do you think? Is there a problem? thanks for your
time.
It's not the speakers that are causing that, it's the amplifier. You're
hearing the switiching distortion associated with Class A-B amplifiers.

No. Class AB output transistors remain on with low amplitude signals.
Switching only occurs with loud signals (How loud depend on the
biasing of the output stage)

Also, this is noise, not distortion.

The noise that is heard is the sum of all noise sources in the signal
chain. The reason it becomes louder when the volume goes up is that by
doing that the noise before the volume control stage dominates. The
noise when the volume is fully off is primarily from the power amp,
but also some from the pre-amp output stage.

The source of the noise likely mostly thermal and shot noise.

Obviously as long as you must be within 5 cm from the speakers to hear
it it is not a problem.

Wires are definetly a red herring.

The switiching distortion is usually very small when compared to the
audio signal. If you had a Class A amplifier connected to your speakers
you would here nothing at all, even at full volume. Class A design
virtually eliminates switching distortion. The drawback to class A is
that amps of that design consume alot of power and generate alot of heat.

Actually if the noise is primarily thermal noise it will increase if
the device is hotter. Not that a class A design is neccecarily hotter
than a comparable AB design, it just generates more heat as you say.
(Those that are confused by this need to review their thermodynamics
:-)


Nothing to worry about. It's normal.

Agreed.


CD

--
They both savoured the strange warm glow of being much more ignorant
than ordinary people, who were only ignorant of ordinary things.
-- Discworld scientists at work (Terry Pratchett, Equal Rites)