How Preouts Work?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=63745
Printed Date: May 27, 2024 at 3:07 PM
Topic: How Preouts Work?
Posted By: a454nova
Subject: How Preouts Work?
Date Posted: October 03, 2005 at 9:10 PM
I think I know the answer to this but want to ask to make sure before I cost myself a lot of money. What comes out of the preamp, in other words here what im asking. What dose the amp need to work, what type of signal? Im going to use a laptop in place of a head unit. I need to know the difference between the laptop output and what a headunit put out to the amp. The laptop is just the headphone jack and I know theyre not the same. Also what is the difference between the perouts on a tv vs a head unit. Thanks ahead for the help. -Matt
Replies:
Posted By: DYohn
Date Posted: October 03, 2005 at 9:22 PM
A pre-amp output is a pre-amp output. The only difference between them is the voltage level they are capable of. The headphone output from your laptop may or may not work depending on the amplifier, but your sound-card may have a "line level" output. Line level is a pre-amp output. The main problem using a laptop can be introducing a ground loop, especially if you try to power it off the vehicle's electrical system. ------------- Support the12volt.com
Posted By: Blowntweeters
Date Posted: October 03, 2005 at 9:26 PM
it depends on what preotus on a H/U. you can us the head phone jack from the laptop ,and do the sugrey on a set of rca's. worst case you will have your preouts a bit weak. i would get a H/U with an aux input and put the signal from the laptop in there.
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1974 ford pinto 4 15" punch Z power punch bd 1001 pioneer DEH-6700
Posted By: a454nova
Date Posted: October 03, 2005 at 9:39 PM
DYohn] wrote:
pre-amp output is a pre-amp output. The only difference between them is the voltage level they are capable of. The headphone output from your laptop may or may not work depending on the amplifier, but your sound-card may have a "line level" output. Line level is a pre-amp output. The main problem using a laptop can be introducing a ground loop, especially if you try to power it off the vehicle's electrical system.
Like noice?
Posted By: stevdart
Date Posted: October 03, 2005 at 9:51 PM
Yes, a ground loop is noise caused by the electronic component picking up inherent noise from the car's electrical system...an electrical system that includes every bit of metal connected to the car.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: a454nova
Date Posted: October 03, 2005 at 10:05 PM
I got the car adaptor for my laptop and running the amps of the headphone jack there is no noice. But I think they are running a little hotter then normal. Before Ive ran the same amp off a deck and i dont think they ran hot. But everything sounds good with the laptop. I just thought that the laptop output (headphone output) is pushing the wrong way.
Posted By: DYohn
Date Posted: October 03, 2005 at 10:06 PM
Did you set the gain on the amp to match the laptop output? ------------- Support the12volt.com
Posted By: a454nova
Date Posted: October 03, 2005 at 10:11 PM
just to make sure. Maybe Im wrong, The perout on a head unit is a steady line lever were the voltage determinds the volume on the amp were the laptop it all raises? This is what Ive always thought.
Posted By: a454nova
Date Posted: October 03, 2005 at 10:12 PM
DYohn] wrote:
id you set the gain on the amp to match the laptop output?
how do I match it?
Posted By: redpeppers
Date Posted: October 03, 2005 at 11:25 PM
one thing i that would benifit u if u door use ur laptop is to get a line driver....they r cheap and they will step the preamp voltage from the laptop up to a high 3 or 4volt gain.....
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Where theres is a wire there's a way.
Posted By: a454nova
Date Posted: October 04, 2005 at 3:32 AM
a454nova wrote:
DYohn] wrote:
id you set the gain on the amp to match the laptop output?
how do I match it?
I found the the laptop put out 2v and the amp is set for that. Is that all that needs done? Im still confused. Is it the same type of output? It cant hurt the amps? In other words the way a head unit would supply the amp is the same as the laptop will?
Posted By: DYohn
Date Posted: October 04, 2005 at 8:43 AM
a454nova wrote:
a454nova wrote:
DYohn] wrote:
id you set the gain on the amp to match the laptop output?
how do I match it?
I found the the laptop put out 2v and the amp is set for that. Is that all that needs done? Im still confused. Is it the same type of output? It cant hurt the amps? In other words the way a head unit would supply the amp is the same as the laptop will?
It won't hurt your amps. Set the gain the same way you would with any other source. Do not trust the markings on the amp. The easiest way to do it is to download a test tone to your laptop. Connect it to your system. Get some hearing protection. Turn the amp gain all the way down. Play the test tone and increase the volume until you hear distortion. turn it back down just until it clears. This is your maximum volume setting and can never be exceeded (this is where the sound card clips.) Turn the gain on the amp up slowly until the distortion comes back. Turn it back down until it clears. Leave it there. Now turn the volume on the computer back down to your normal listening level and you're done. ------------- Support the12volt.com
Posted By: a454nova
Date Posted: October 04, 2005 at 4:28 PM
Thanks for the help! On another note now that its all working great. The amp im using is a 200 watts RMS, bridged. When the bass hits its taking a bite out of my trucks power. Any ideas. Is this normal for a amp this small? I took the amp from my brother and was thinking it might have been shorted out. I have a 105 AMP Alternator.
Posted By: stevdart
Date Posted: October 04, 2005 at 6:28 PM
Things you can try: upgrade OEM ground wire from battery to chassis, clean and wire brush connections, turn the amp's gain down a bit... listen to Chopin.... 
------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: a454nova
Date Posted: October 04, 2005 at 7:16 PM
Well after read some here on The12volt, I see that this amp can pull around 32 AMPs. I didnt know that. Its prob that the 105 AMP Alternator isnt big enough. Ill try the ground. That makes since. Thanks!
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