Line-out vs. Speaker out (Soundcard)
William Lanford
Hi,
What is the difference between the line-out and speaker-out on my sound
card? I suspect that the speaker out is impedence-matched to an 8 ohm
speaker (signal comes from a transformer) and has greater voltage
amplitude. What is the specification for "line (in/out)" signals?
What are the consequences of connecting the speaker out of my sound card
to the line-in of my stereo? Clipping? Is there any danger to the stereo
amplifier?
thanks,
Bill
Tom MacIntyre
Don't know the exact specs, but impedance is probably the key here.
The speaker out is likely 8 ohms, and would have a power amplifier
feeding it, with maybe a maximum of 1.5W of output. The line out would
have a higher impedance; guesses would be 150 - 600 ohms if low, or
10k - 20k if high. The signal level from the line out is low, in the
order of millivolts.
I've seen other low-powered speaker outputs being used to feed a line
in on an amplifier. You may have a hum problem, and/or clipping if the
output levels from the soundcard are turned up too high. If you do try
this, make sure that the audio level on the stereo amp AND the
soundcard are down all the way to start. I assume there's a reason why
you want to use the speaker output instead of the line out, so I won't
ask.
Sam Goldwasser
Line out is in the 1-2V range p-p and not designed to drive a low impedance
like a speaker. Speaker out will be roughly V*V/R max for whatever speaker
impedance and power rating is specified for the card. For a 3 W sound card and
8 ohm speaker, this would be about 5 VRMS.
One some sound cards, it is possible that their amplitude is controlled
independently - don't know.
As far as damage or clipping, clipping is likely if your sound card volume is
turned up if input from the speaker out. Damage? Probably not from the
whimpy amps in a sound card unless you turn your BIG amp all the way up and
get the clipping and your speaker cones go flying across the room :-).
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!
Jerry G.
The line out on your sound card is meant to drive another pre-amp or powered
speakers that use line level in.
The speaker out is generaly an 8 ohm high level out. On most sound cards it
can put out about 2 to 5 watts depending on the card. I would not put this
output into the line in of an amplifier!!! It will certainly overdrive the
input, and may damage the input transistors or IC's.
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============= Message Seperator ================
William Lanford wrote in message <354EA5...@princeton.edu>...
|Hi,
William Lanford
Tom MacIntyre wrote:
>
> soundcard are down all the way to start. I assume there's a reason why
> you want to use the speaker output instead of the line out, so I won't
> ask.
>
Actually, I ask because I discovered (after the right channel on my
stereo started acting funny) that I had the speaker out hooked up to my
stereo, which was not what I had intented. The symptoms suggest that
this may not have been the problem, but once several years ago my right
channel first started buzzing along with the music, and then outputed
ONLY buzzing. While this occurred (and prior to it), I had had the
speaker outputs of a record player (it didn't have a line out) connected
to a line-in on my stereo (I didn't know better then), so I suspected
that that may have caused the problem.
I am interested in knowing if having the speaker-out connected to
line-in could have caused the damage, or if was just coincidence.
With the record player, I had been careful to keep the record players
volume low enough so that the output volume was about the same as for
other line-in devices with the stereo at the same volume. I had thought
this would be safe, but that was before I knew what impedence was. Now
I know how to calculate impedences, etc... but I'm afraid that I really
do not what the "impedence of an ouput" is.
Bill
Niall
On Tue, 5 May 1998 22:04:31 -0400, "Jerry G." <jerr...@hotmail.com>
wrote:
>The line out on your sound card is meant to drive another pre-amp or powered
>speakers that use line level in.
>
>The speaker out is generaly an 8 ohm high level out. On most sound cards it
>can put out about 2 to 5 watts depending on the card. I would not put this
>output into the line in of an amplifier!!! It will certainly overdrive the
>input, and may damage the input transistors or IC's.
>
Using a speaker output into a line input usually works pretty well.
Because the input impedance of the line input is much higher than 8
ohms (usually >10K) the sound card cannot deliver 5 watts into the
line input.
What is critical in input terms is the voltage, which for 5 watts into
8 ohms would be about 6.3 volts. Remember this is at full power, and
assumes RMS watts; souncard outputs are quoted watts PMPO at best,
usually Totally Imaginary watts, so actual max. power will be much
less.
Line inputs can usually cope with up to 2v, CD inputs are specified
for 2v, so not far off if the card output is turned down a bit.
Loading the output with a 5w 8ohm resistor might reduce the distortion
a bit.
This does not mean that you can attach a line input to a hifi or pro
amp output without some kind of matching network as the power output
and hence max. voltage swing is much higher, but for low power devices
it works fine.
Niall