Can you split a preout signal without degrading the signal? - AVS | Home Theater Discussions And Reviews
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post #1 of 9 Old 10-30-2012, 07:37 AM - Thread Starter
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Can you split a preout signal without degrading the signal?

I am splitting an integrated amp's preout signal and sending the signals to two different amps, both of which are within six feet of the integrated amp. I don't hear signal noise but I also don't have a golden ear.

Am I introducing noise? Or is the signal strong enough to be split happily?
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post #2 of 9 Old 10-30-2012, 08:15 AM
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I'm not sure what you mean by degrading, but you'll reduce the voltage by splitting it. In theory, you'll get the same wave form but at a lower amplitude.
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post #3 of 9 Old 10-30-2012, 08:22 AM
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The voltage is not reduced except under the rare condition* that the reduced load is excessive.  Normally, the output of each amplifier is unaffected in amplitude or quality.

 

(*Paralleled loads split the current and voltage is compromised only if the current capability of the source is exceeded. With normal amp input impedance, this is unlikely.)


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post #4 of 9 Old 10-30-2012, 08:51 AM
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Noise should not be an issue.

If one or both of the amplifiers had an input impedance less than 5K ohms, you might load down the preamp signal enough to create some interfacing problems, but this is not likely. Most amplifiers have a much higher input impedance.

It sounds as if it is working fine, so there is no need to concern yourself.
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post #5 of 9 Old 10-30-2012, 10:27 AM
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Quote:
Originally Posted by Kal Rubinson View Post

The voltage is not reduced except under the rare condition* that the reduced load is excessive.  Normally, the output of each amplifier is unaffected in amplitude or quality.

(*Paralleled loads split the current and voltage is compromised only if the current capability of the source is exceeded. With normal amp input impedance, this is unlikely.)

I would be very surprised if maintaining the same volume for each amp didn't require turning up the volume. I've never split a signal without amplification where there wasn't a loss in signal strength.
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post #6 of 9 Old 10-30-2012, 10:33 AM
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Quote:
Originally Posted by KidHorn View Post


I would be very surprised if maintaining the same volume for each amp didn't require turning up the volume. I've never split a signal without amplification where there wasn't a loss in signal strength.

Not my experience and not what theory would predict.  The preamp output is modulated voltage signal and the amp input stage detects voltage.  Assuming the two amps are identical, the only reason that the voltage seen by each of the two amps would be if the preamp output stage had inadequate current to maintain the same/original voltage across half of the original load.  Unless the amps had an atypically low input impedance or the preamp was a real weakling, that would not occur.  As I said, in my experience that won't happen.


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post #7 of 9 Old 10-30-2012, 11:16 AM
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A quick glance at a few spec sheets seems to run around 10k ohms for amp inputs and 100 ohms for preamp outputs. Assuming a perfect source before the preamp Rout, the input voltage at one amplifier is thus 10000/10100 = 0.9901 V for a 1 V source (-0.086 dB). With two amps in parallel the load is now 5k so 5k/5.1k = 0.9804 V (-0.172 dB), a difference of 0.0856 dB (about 0.01 V). Really doubt you'd hear that... I am sure there are exceptions, but in general I agree with Kal. Natch.

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post #8 of 9 Old 10-30-2012, 11:26 AM
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You should be fine...
Assuming the preamp is a quality name brand...
Not some low end junker...


Just my $0.02.. wink.gif
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post #9 of 9 Old 10-31-2012, 12:05 PM - Thread Starter
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Yes, it does sound fine. And when it sounds fine, it's all fine.
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