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Old 05-31-2006, 11:30 AM   #1
cambam
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Info About Pre-Out Voltage And Lots More

Hey guys, you may have read this somewhere before, it has alot of info on amplifiers, power, signal to noise, damping, pre-out voltage and more. It seems that some are on the fence for more pre-out voltage the better. But on page 4 from this link, as long as your head unit produces the minimum input voltage of the amp, then you will be able to get all of the power from the amp. Example: if the amp has a minimum input voltage of .250v and a maximum of 5v, all you need is .250v to get all the amp has to offer. Any less, then that 400w rms amp you just bought will not beable to reach its potential. So the way I see it, the difference between a 2v, 4v, or 5v pre-out head unit only means you will get the max from the amp sooner with the higher voltage over the lesser one. But in the big picture, it really only matters that you have the minimum which is usually less then about .400v. http://www.jbl.com/car/support/AUTOMEDIA_CEA2006.pdf

I meant to put INFO about....... not Facts about......in the thread name.



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Old 05-31-2006, 12:44 PM   #2
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more info and facts.... (since we are on the same topic)

www.bcae1.com
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Old 05-31-2006, 03:58 PM   #3
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Plain and Simple.... keeping the amp gains down will give you a cleaner sound.

If the HU clips at 80% volume, and the unit was rated 5v, then you might be lucky to have 3.5-4v at the new max volume setting of 80%, so you'd then want an amp that is 2.5 to 4v on the gain pot.

Example: my DRZ puts out 4v at full volume, but I rarely turn it up that far. The Arc amp gains are all the way down (at 2.5v), so my general listening level is right at the exact voltage. So you see, I'm the other way around, I have a higher pre-out voltage than what the amp is rated to use.... and that was the plan. Get it?

You want a high S/N ratio to keep the noise floor down.

Ok, this is the simplest way to look at it: The amp amplifies what it is given. So, the higher the pre-out voltage, the higher the S/N ratio (signal-to-noise). When you amplify the signal, you also amplify the noise floor along with it. Again, you want some distance between the signal level and the noise level prior to the amp (pre-amp voltage).

The higher voltage for a higher S/N ratio gives you the cleanest signal. Then keeping the amp gain down, you keep the amp cooler, less distortion, less potential for coloration, etc etc.
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Old 05-31-2006, 04:19 PM   #4
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I am gonna guess that the LOC's varible settings are good from 0.5v-3v?

Nevermind, I answered my own question.
David Navone LOC's output 0-9.5v
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Old 06-01-2006, 03:09 AM   #5
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Wow, 9.5v is plenty.

The downside to using that setup is being limited to the stock stereo's DACs, then an inferior internal amplifier coloring the audio, then converting that back with the LOC, then to the amp to be amplified. I only suggest keeping and using a stock unit if the overall system is going to be a budget system.

Unless, like some units allow, you can modify the stock HU for an optical output, then you can connect an Alpine PXA-H701 processor with the C701 controller for a great SQ setup using the stock HU as a CD transport.
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