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Old 08-18-2011, 12:32 AM   #1
gsxtasy

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JL 500/1 Input Sensitivity Setting-Low output voltage

Alright, so I have this JL 500/1, and I just put in a new 8w7 and hooked it all up and it was pretty quiet, so I went to adjust the input sensitivity as described by the manual.

So I get it all setup, and even with the gain all the way clockwise, while running a 50hz sine tone, I am still only getting around 5.5v on the sub output terminals. It's supposed to be up to 38.7v for a 3 ohm sub.

I don't know too much about this stuff, so does anybody know is this a problem with the amp/amp settings, or headunit problem, or bad RCA's?

I'm using an Alpine CDE-126BT headunit.
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Old 08-18-2011, 12:38 AM   #2
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Quote:
Originally Posted by gsxtasy View Post
Alright, so I have this JL 500/1, and I just put in a new 8w7 and hooked it all up and it was pretty quiet, so I went to adjust the input sensitivity as described by the manual.

So I get it all setup, and even with the gain all the way clockwise, while running a 50hz sine tone, I am still only getting around 5.5v on the sub output terminals. It's supposed to be up to 38.7v for a 3 ohm sub.

I don't know too much about this stuff, so does anybody know is this a problem with the amp/amp settings, or headunit problem, or bad RCA's?

I'm using an Alpine CDE-126BT headunit.
the JL audio slash series amplifiers have a switch on them that changes the values for the input sensitivity knob. Try flipping that switch. Your radio shows that it only has a 2v pre-out, and If the switch on the amp is flipped to high then your telling the amp your sending it a higher amout of voltage to amplify than you really are. I may be mistaken, but give it a try and see where it goes.
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Old 08-18-2011, 12:41 AM   #3
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Quote:
Originally Posted by rocker_topper View Post
the JL audio slash series amplifiers have a switch on them that changes the values for the input sensitivity knob. Try flipping that switch. Your radio shows that it only has a 2v pre-out, and If the switch on the amp is flipped to high then your telling the amp your sending it a higher amout of voltage to amplify than you really are. I may be mistaken, but give it a try and see where it goes.
I had the 'input voltage switch' set to low, as the manual recommends. I also tried it on high and it makes the voltage even lower.
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Old 08-18-2011, 12:50 AM   #4
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Quote:
Originally Posted by gsxtasy View Post
I had the 'input voltage switch' set to low, as the manual recommends. I also tried it on high and it makes the voltage even lower.
hmm.... try pulling one side of your rcas out of the amp to see if the signal changes any. Its possible you could have a faulty amplifier. It happens sometimes. We had a brand new, direct from JL 250/1 shipped to us that when no remote, but power and ground were applied the amp would come on. They pump out enough that they are bound to miss a bad one every now and then. And it could have been fine whenever it left the factory but maybe somehow got damaged in shipping. The soulder on those boards can be brittle and its possible if the box was dropped the impact could have broken something lose inside the amp.

Last edited by rocker_topper; 08-18-2011 at 12:55 AM.
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Old 08-18-2011, 01:03 AM   #5
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It's a v1 amp, so it's an older amp, so it very well could be something faulty in the amp. Just the sub is new. I just found it odd that it will work and sounds decent, just not a lot of ouput from the sub. I'll go give your suggestion a try, thanks!

I had the amp hooked up to a 10'' type-r previously and it was working fine, then one day the sub sounded distorted and crappy. The low-ohm light illuminated on the amp and I don't know why...it was wired at 4ohms. So i thought maybe the amp was toast, but I unhooked the sub and the light went away and i thought I'd give it a try again. So i bought this sub and hooked it up, then came to realize my RCA's must have been the faulty problem, so I threw on a set I had laying around and am to the problem I have now. Sub sounds good and clean, just low output.

Last edited by gsxtasy; 08-18-2011 at 01:07 AM.
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Old 08-18-2011, 01:05 AM   #6
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sure thing, let me know what you find out.
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Old 08-18-2011, 01:29 AM   #7
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Alright, so if I unhook either RCA voltage drops to essentially zero. I also tried another set of RCA's just to triple check, same thing.
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Old 08-18-2011, 02:25 AM   #8
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Quote:
Originally Posted by gsxtasy View Post
Alright, so I have this JL 500/1, and I just put in a new 8w7 and hooked it all up and it was pretty quiet, so I went to adjust the input sensitivity as described by the manual.

So I get it all setup, and even with the gain all the way clockwise, while running a 50hz sine tone, I am still only getting around 5.5v on the sub output terminals. It's supposed to be up to 38.7v for a 3 ohm sub.

I don't know too much about this stuff, so does anybody know is this a problem with the amp/amp settings, or headunit problem, or bad RCA's?

I'm using an Alpine CDE-126BT headunit.
Was the meter set to AC or DC?

Check your HP/LP settings. Did you check pre-amp voltage?
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Old 08-18-2011, 02:51 AM   #9
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Meter set to AC.

I had the LP filter on the amp set to 24db slope and around 85hz. This could be wrong, this is what I found in the manual to set it at?

Infrasonic filter was off, bass EQ was off.

I didn't check pre-amp voltage. Sorry for the incompetence, but do I just put my dmm on the RCA's to check this?
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Old 08-18-2011, 03:20 AM   #10
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Quote:
Originally Posted by gsxtasy View Post
Meter set to AC.

I had the LP filter on the amp set to 24db slope and around 85hz. This could be wrong, this is what I found in the manual to set it at?

Infrasonic filter was off, bass EQ was off.

I didn't check pre-amp voltage. Sorry for the incompetence, but do I just put my dmm on the RCA's to check this?
Yeah, just check the voltage at the RCA cable.
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Old 08-18-2011, 03:32 AM   #11
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does the deck have a subwoofer volume?
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Old 08-18-2011, 03:45 AM   #12
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Yes, I had it turned up 3/4 of the way as well.
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Old 08-18-2011, 02:34 PM   #13
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Infra sonic filter : set it to 25 Hz for a sealed box, and 3 to 4 hz below box tuning for a ported box.
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Old 08-19-2011, 12:05 AM   #14
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Quote:
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Infra sonic filter : set it to 25 Hz for a sealed box, and 3 to 4 hz below box tuning for a ported box.
I tried it both ways, but JL recommends that the infra sonic filter be set to off for sealed enclosures and either way didn't solve the issue. Thanks for the suggestion though!
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Old 08-19-2011, 04:30 AM   #15
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After some help and more diagnosing, it appears to be a head unit issue. It is not providing enough voltage to the pre-outs. With a 50hz sine wave playing at 80% volume I am only getting around 100mV to the sub outs on the head unit.... I am unsure why, as this head unit is only a few months old.
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