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Old 13th August 2004, 06:35 AM   #1
memito is offline memito  United States
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Default Amp Controls

I'm a moron, I'll be the first to admit it when it comes to car audio. I recently got interested in these things and installed a system on my car, but now I need help adjusting the controls on my amp. This particular amp (hifonics brutus) is running a 12" JL sub, but I have no clue what any of the knobs do. Below are the knobs and their values.

1. Subsonic (15-35hz)
2. Bass EQ (0-18db)
3. Low Pass (35-250hz)
4. Phase (0-180 degrees)
5. Level (9-0.2 Volts)

If anyone out there knows what any of them do and the best setting for this particular speaker I would appreciate the help, thanks.
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Old 13th August 2004, 12:05 PM   #2
tuneman is offline tuneman  Australia
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ok!

subsonic is what is used to cut the really low frequency signal from the amps output, usefull for ported boxes that will be unloaded at these low freq's, it helps protect your subs, can be set by ear later on.

bass eq? sounds like a bass boost giving you up to 18db gain, use it sparingly

low pass is what freq your subs run from! eg if you set it on 35hz it would play only below 35hz, if its on 250hz only below 250hz, or if on 80hz everything below 80hz(probably the best spot but it can be ajusted when its playing to get the best spot!)

phaze is your phasing for the sub in this case it does the same thing as switching the wires around on the sub, normally it would be left on 0 but if for some reason it sounds bad or theres no bass or its been wired the wrong way just flick the switch and see if it sounds better.

level is the amps gain, it is not a volume control!! it is to compensate for your decks output or whatever is before it, it says .2 - 9v!, 9 volt is the maximum signal voltage the inputs can handle, .2 is the lowest it can use' if your deck had only a 4v output the level is to compensate for it not being 9v and it would be need to be turned up a bit, it you hade a very high volt deck that put out 9v it would stay at minimum.
its position needs to be set in acordence with the deck you have so you need to do the whole level setting procedure, hopfully someone else can explain that cause i have to go
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Old 13th August 2004, 04:00 PM   #3
maylar is offline maylar  United States
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Leave subsonic filter off or set to 15 Hz.
Leave bass eq off (zero)
Set lowpass to 80 Hz for starters. You can fine tune this later.

Like the guy said above, the gain cntrol sets the sensitivity of the amp and the maximum power it'll put out. There are tutorials on the web for setting that. The basic procedure is to play some heavy bass music with your HU at 3/4 volume and turn the gain up until the power limit is reached then turn it down a bit.

Power limit is when either the subs or amp can't do any more without distorting. If the subs reach their limits first, they'll make nasty noises when you go too far. If the subs can take the full power of the amp then you need to set the gain control for the amps rated output... JL Audio's web site has a tutorial on doing that with a DMM.
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Old 13th August 2004, 04:34 PM   #4
memito is offline memito  United States
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Thanks

just one more question, is it normal for the Level to START at 9volts and go down to 0.2volts. 'Cus on this amp that's the way it's set, 9volts is on the left and 0.2volts is on the right.
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Old 13th August 2004, 05:25 PM   #5
memito is offline memito  United States
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OK, i've been going over the instructions on the jl to set the gain but i'm not getting the whole voltage thingy. I downloaded a test tone off the net which was recorded at 50khz with a decible gain of -10. I then modified the decible gain on the sound file to be at 0db. The part i'm having trouble with now is figuring out the optimum voltage that the amplifier should be set to. How can i figure out that? According to the chart on the JL website there's two types of amps, "slash" and "e" series (i'm guessing those are the amps that jl sells). How could I know the values for my specific amp and speaker?
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Old 13th August 2004, 08:13 PM   #6
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I personally would set the gain as follows:
- Use a voltmeter to determine the voltage of the input signal (your RCAs or speaker-level wires, whichever you are using).
- Then set the dial to that number. If it's 9v set the dial all the way to the left, if it's 4.6v set the dial right in the middle, if it's .2v set the dial all the way to the right, etc ... On a sidenote, it is generally a good idea to have the dial set a little bit lower (counter-clockwise) than the determined setting, so as to not over-work your amp.

Oh, and the phase can be used to fine-tune WHEN the bass hits. Generally it is a good idea to just leave it at 0, but if the bass from your subs is not hitting at the same time as your other speakers, try adjusting the phase. Really though, it is unlikely that you would be able to hear it; you'd have to really know what you're listening for.

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Old 13th August 2004, 09:43 PM   #7
memito is offline memito  United States
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thanks, but how can i determine the voltage of the rca's?
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Old 14th August 2004, 12:15 AM   #8
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read this page . ..
Amplifier Gain Controls
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Old 14th August 2004, 05:41 AM   #9
memito is offline memito  United States
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Ok, I read the tuturial, but I still can't figure out how to calculate or know the output voltage of my head unit. I think I understand everything, matching gains on both head unit and amp, but to do that I must first know what my HU is outputting as it's voltage at around 75% it's power right? Once that happens, then I can start adjusting the gain on my amp to get it to match the HU, right?
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Old 14th August 2004, 10:29 PM   #10
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You're on the right track now . .. Go to BCAE1.com to learn how to use a multimeter, and determine your voltage. I can not just tell you the best way to test them, as what you check will depend on how you plan to set it . . So, browse that site a little, and you will find the answers you are looking for . ..
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