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    Need help with strange gain knob

    I have been searching threads all night long and am still unable to find exactly what I am looking for. Anyways, my amp is a jbl1201.1. Two RF P3 subs with 4 ohm impedance are being powered at 2 ohm impedence wiring at 1114 watts. It is a mono amp so from what I have read the gain should be at around 33.37 volts. Sqrt 1114=33.37 The part where I get confused is on the gain knob. It is called the input level wich I have figured is the gain. On the left it starts at 6v and goes clockwise to the right to 250mv. I have been unable to find what mv stands for. I just really need help setting the gain on this amp. I can do it by ear but I want to make sure I start at the 6v and move clockwise towards the 250mv. This is probably the only way to do it since there are no numbers inbetween to know where it is set. Any information as to what you see wrong or right with this would be extremely appreciated. My email is [email protected]

    Thanks for reading.







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    Re: Need help with strange gain knob

    Start all the way counter clock-wise, play your tone and increase the gain till you get your desired voltage that you better be reading with a DMM....



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    Re: Need help with strange gain knob

    Quote Originally Posted by cutthrough
    I have been searching threads all night long and am still unable to find exactly what I am looking for. Anyways, my amp is a jbl1201.1. Two RF P3 subs with 4 ohm impedance are being powered at 2 ohm impedence wiring at 1114 watts. It is a mono amp so from what I have read the gain should be at around 33.37 volts. Sqrt 1114=33.37 The part where I get confused is on the gain knob. It is called the input level wich I have figured is the gain. On the left it starts at 6v and goes clockwise to the right to 250mv. I have been unable to find what mv stands for. I just really need help setting the gain on this amp. I can do it by ear but I want to make sure I start at the 6v and move clockwise towards the 250mv. This is probably the only way to do it since there are no numbers inbetween to know where it is set. Any information as to what you see wrong or right with this would be extremely appreciated. My email is [email protected]

    Thanks for reading.
    mV=millivolt...1000mV=1V

    You will need to buy a DMM (digital multi meter), You will not be able to set the 33.xxV you want by ear.

    EDIT: read this....http://www.caraudio.com/vb/showthread.php?t=63933
    Last edited by Johnny Drama; 11-07-2005 at 10:49 AM.




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    Re: Need help with strange gain knob

    Ok so lets see if I understand this. 1000mv=1v So 250mv would be .25v So that means that the gain goes from 6v to .25v, and I start on the 6v and work towards the .25v. Also, is the meter to test it with a must, or can I just set the volume and then turn the gain until it distorts. That method.




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    Re: Need help with strange gain knob

    if you are going to set the gain by ear then you are defeating the purpose of finding out the AC voltage reading you calculated earlier. what you need is a multimeter. set it to read AC voltage. put the red and black probes on the + and - of the speaker ouput. adjust the gain till you get the desired voltage reading.




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    Re: Need help with strange gain knob

    Quote Originally Posted by cutthrough
    Ok so lets see if I understand this. 1000mv=1v So 250mv would be .25v So that means that the gain goes from 6v to .25v, and I start on the 6v and work towards the .25v. Also, is the meter to test it with a must, or can I just set the volume and then turn the gain until it distorts. That method.
    You can do it by ear.




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    Re: Need help with strange gain knob

    As Squeek said, you can do it by ear. You can also do it with the DMM. Neither are completly accurate, but the DMM is much closer and runs a much lower risk of clipping.




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    Re: Need help with strange gain knob

    Ok I got a hold of a DMM. I just wanted to make sure the voltage is correct. 1114 watt output for 2 subs wired for 2 ohm resistance going into the mono amp. So is 33.37 volts right. Just the sqrt of 1114 right? Since it is a mono amp?




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    Re: Need help with strange gain knob

    No. Voltage is the square root of power times ohms. In your case 1114 watts and 2 ohms gives 47.2 volts ac rms. Do this with a 50 hz tone CD, your eq settings at normal listening, hu volume at 3/4 and with NO SUBS attached.

    Personally, I do it by ear. But my criteria is for best tonal balance in the car, not "as loud as possible without distortion".



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    Re: Need help with strange gain knob

    dmm's are cheap anyway, you can pick one up at wal-mart for like 15-20 bucks. Its a good investment




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    Re: Need help with strange gain knob

    So now I need a cd?? I'd rather not buy one buy one because I live in the middle of bum fu** and it takes an hour and a half to get to the nearest city the would be selling this item. And to buy it from the internet would take to much shipping time. So could I either use a normal cd, or maybe there is somewhere you know of where you can download one of the tuning cds.

    Thanks, you guys have been helpful.




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    Re: Need help with strange gain knob

    Quote Originally Posted by cutthrough
    I have been searching threads all night long and am still unable to find exactly what I am looking for. Anyways, my amp is a jbl1201.1. Two RF P3 subs with 4 ohm impedance are being powered at 2 ohm impedence wiring at 1114 watts. It is a mono amp so from what I have read the gain should be at around 33.37 volts. Sqrt 1114=33.37 The part where I get confused is on the gain knob. It is called the input level wich I have figured is the gain. On the left it starts at 6v and goes clockwise to the right to 250mv. I have been unable to find what mv stands for. I just really need help setting the gain on this amp. I can do it by ear but I want to make sure I start at the 6v and move clockwise towards the 250mv. This is probably the only way to do it since there are no numbers inbetween to know where it is set. Any information as to what you see wrong or right with this would be extremely appreciated. My email is [email protected]

    Thanks for reading.
    H/O, is this 2 2 ohm dual voice coil subs or 2 4 ohm dual voice coil subs, because if they are the latter, you do NOT want to run them at 2 ohms, you want to run them at 1, but if they are DVC 2 then you are fine.

    Quote Originally Posted by cutthrough
    So now I need a cd?? I'd rather not buy one buy one because I live in the middle of bum fu** and it takes an hour and a half to get to the nearest city the would be selling this item. And to buy it from the internet would take to much shipping time. So could I either use a normal cd, or maybe there is somewhere you know of where you can download one of the tuning cds.

    Thanks, you guys have been helpful.
    You can just download a test tone and put it on a cd...





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    Re: Need help with strange gain knob

    it is 2 dvc 4 ohm subs. But they are not wired together. They are each wired by themselves to two ohms. There are two outputs for the subs on the amp even though it is a mono amp. I am able to do this right?




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    Re: Need help with strange gain knob

    its a jbl 1201.1 if you need to look at it to understand cuz i'm not good at explaining things




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    Re: Need help with strange gain knob

    Ya, even though it has 2 inputs it parrallels inside, but as long as you have both wired in parrallel then you're fine.





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