# Need Help With My Amp JBL MS-A1004



## Rectorna (Feb 14, 2012)

I am having a problem with the output volume of my amp. I have the amp hooked up to a set of component speakers up front and a sub in the back. The amp has a analog to digital converter or something along the lines of that. The problem is there are something called Input Level control and from what I can tell from reading the manual its seems to have something to do with the analog to digital conversion. Is that correct?
There are two knobs that control this Input level control, one for each set of RCAs. The manual has me playing a song with the head unit at full volume and the putting the amp in a special setup mode and then wants me to adjust the Input Level control, and there is even up and down arrows on the screen to show you exactly where it should be. The problem is where the amp is telling me to tune is relatively low compared to how far the knob will turn. I have both of the Output Gains set on their max of 80 though the screen but the music is fairly quite, which is no problem because it goes the whole length of the volume control on my head-unit but, I can barley hear the sub. If I turn the channel 3 and 4 Input Level knob higher the sub actually gets loud, but the manual says to not use that knob to adjust output level, so I am lost. :banghead:

What exactly is that control for and what should I do regrading turning it up more to get more out of the sub?

Thanks!

Here is the link to the book for the amp. 
http://www.jbl.com/images/media/MS_A1004_OM_ML.pdf

Its the one marked level in the picture.


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## nineball (Jan 17, 2008)

the input gain pot (labeled LEVEL in your pic) is used to match the input signal the amp is receiving. the output gain (that you have set at 80) is used to level match channels 1/2 to channels 3/4. 

what are you using for a signal? if rca from an aftermarket hu you should set the switch to LO. if you are using high level (speaker wire) start with it on HI and follow the instructions. you can also try it on HI2 but you will have to start over with the cd and gain adjusting as it will be different than HI.


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## Rectorna (Feb 14, 2012)

I am still a little bit confused on the whole Input gain vs Output gain.
Signal is coming from an aftermarket Pioneer App Radio. It only has 1 preout so I have it split into two, to run the front components and the Sub bridged in the back. I thought the High and Low was high pass filter and Low pass filter? EDIT (after reading the book some more turns out i'm and idiot for thinking that those were high/low pass filters. What exactly does that switch do then?)

The book says to not use HI2 with RCA outputs.

Thanks for the help!



nineball said:


> the input gain pot (labeled LEVEL in your pic) is used to match the input signal the amp is receiving. the output gain (that you have set at 80) is used to level match channels 1/2 to channels 3/4.
> 
> what are you using for a signal? if rca from an aftermarket hu you should set the switch to LO. if you are using high level (speaker wire) start with it on HI and follow the instructions. you can also try it on HI2 but you will have to start over with the cd and gain adjusting as it will be different than HI.


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## nineball (Jan 17, 2008)

the ms series amps are amazing pieces. i highly suggest you read every page of the manual, watch some tv, then read it again cover to cover. it explains how everything works in fairly simple terms. 

you don't need to split your rca cable, the amp can do that for you. the last of the system diagrams in the manual has speakers on channels 1/2 and the sub bridged on 3/4. it also shows what the display should look like. you want to do the exact same thing with 2 exceptions:

1 only have rca cables feeding 1/2 input 
2 on the display, lower left corner, you will see where it says "3,4" and just up and to the right you will see "3" alone. you want to change the "3" to read "1,2" just as it does above. 

the LO/HI/HI2 switch is positioned based on your input signal. rca cables, also known as low-level, need the switch on LO. speaker wire inputs, or high-level input, like directly from a hu, require the HI point be used and sometimes the HI2.

in simple terms the input gain matches the internals of the amp to the signal it is receiving, it is not a volume knob. search on here for "clipping level" when you have some free time. the output gain on your amp does function similar to a volume knob and allows to you level match (volume) channels 1/2 to 3/4. 

i'd suggest you start from scratch. set all hu settings to 0, play the cd, set the input gain and start with the output set at 50. if the sub is too loud you can adjust the front speakers high, or vice versa. you want to end up so that one is not overpowering the other. starting at 50 allows you room to increase one to match the other. remember to set your crossover points as well (i'd suggest 100hz).

again, read your manual. it will explain all of this in great detail with pics to help. if you are still stuck the harmon customer service is damn good.


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## Rectorna (Feb 14, 2012)

Thanks for all the info! I didn't understand what the LO/HI/HI2 was for which is why I had the RCA split. What should the switch be set on? The book says start on hi and see if it goes green and mine did but you just said LO is for RCA and I am using RCA, so do you know which one I should be using?

Thanks!



nineball said:


> the ms series amps are amazing pieces. i highly suggest you read every page of the manual, watch some tv, then read it again cover to cover. it explains how everything works in fairly simple terms.
> 
> you don't need to split your rca cable, the amp can do that for you. the last of the system diagrams in the manual has speakers on channels 1/2 and the sub bridged on 3/4. it also shows what the display should look like. you want to do the exact same thing with 2 exceptions:
> 
> ...


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## nineball (Jan 17, 2008)

i run all three of my ms amps on low w/ rca inputs.


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## Rectorna (Feb 14, 2012)

I put both of the amps input slectors on low today and redid the CD thing and turned the power down to 50%. The components sounded great but... I can still barley hear the sub where the amp had me set the input level for that channel. Should I just turn the input level for the sub up a little bit? Because it definitely makes the sub louder? If I did turn it up what could be some problems? 



nineball said:


> i run all three of my ms amps on low w/ rca inputs.


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## nineball (Jan 17, 2008)

Rectorna said:


> I put both of the amps input slectors on low today and redid the CD thing and turned the power down to 50%. The components sounded great but... I can still barley hear the sub where the amp had me set the input level for that channel. Should I just turn the input level for the sub up a little bit? Because it definitely makes the sub louder? If I did turn it up what could be some problems?


what sub, amp and enclosure?


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## Rectorna (Feb 14, 2012)

Infinity Kappa 120.9W 12 inch and a sonic brand sealed box. I am running the sub off the same JBL MS-A1004 as the front speakers with channels 3 and 4 bridged.




nineball said:


> what sub, amp and enclosure?


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## nineball (Jan 17, 2008)

what size box? that has a lot to do with a sub's performance. also keep in mind you are feeding the sub roughly half of the power it is rated for.


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## Rectorna (Feb 14, 2012)

1 Cubic foot like the sub recommends. I know that it is running at almost half the power. I did find this though that says this amp actually puts out a lot more power than JBL says, the reviews was putting out 406 at 4 ohms. 

PASMAG | PERFORMANCE AUTO AND SOUND - JBL MS-A1004 Amplifier 

But my question is if I turn the Level input clockwise or up for channels 3 and 4 which the sub are hooked up to the sub gets more power it seems because it gets louder.

So what could happen if I turned the level input up some?




nineball said:


> what size box? that has a lot to do with a sub's performance. also keep in mind you are feeding the sub roughly half of the power it is rated for.


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## thomasluke (Jun 10, 2011)

Rectorna said:


> 1 Cubic foot like the sub recommends. I know that it is running at almost half the power. I did find this though that says this amp actually puts out a lot more power than JBL says, the reviews was putting out 406 at 4 ohms.
> 
> PASMAG | PERFORMANCE AUTO AND SOUND - JBL MS-A1004 Amplifier
> 
> ...


Thats the reason you started at 50 for the gain. So you can adjust the sub up a little or the comps down.
Just dont turn the sub up to clipping level. 
To answer your question though the sub will get louder.


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## nineball (Jan 17, 2008)

Rectorna said:


> 1 Cubic foot like the sub recommends. I know that it is running at almost half the power. I did find this though that says this amp actually puts out a lot more power than JBL says, the reviews was putting out 406 at 4 ohms.
> 
> PASMAG | PERFORMANCE AUTO AND SOUND - JBL MS-A1004 Amplifier
> 
> ...



how many times can i say it? the input gain is not a volume control and should not be used like one. period. set it according to the manual and forget you even have an input gain.

the only thing you should be adjusting are the output gains, which is done on the display. set all of them to 50, then start turning 3/4 up until you are happy with it. if you get to 80 and you are still not happy you have 2 choices:

1. turn channels 1/2 down lower than 50

2. buy a different sub, sub amp or both


why does the chart on the link you posted have a "?" after each value? it seems strange that they start off the article by saying the amp produces the same power at 2 or 4 ohm but then the chart says there is a 50% gain on a 2 ohm vs 4 ohm load. i also find it hard to believe that the amp does more than double the rated power when bridged.


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## pjf1fan (Jul 29, 2011)

nineball said:


> why does the chart on the link you posted have a "?" after each value? it seems strange that they start off the article by saying the amp produces the same power at 2 or 4 ohm but then the chart says there is a 50% gain on a 2 ohm vs 4 ohm load. i also find it hard to believe that the amp does more than double the rated power when bridged.


The question marks are there because keyboards do not have an "ohm" symbol. Also, many unregulated amplifiers will double output at two ohms, that's what they are supposed to be able to do if they're engineered right.


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## 14642 (May 19, 2008)

Check the crossover on the amplifier. Make sure that the HP filter on the sub channels reads "off" and the LP filter on those channels reads something like "80".


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## 2DEEP2 (Jul 9, 2007)

Andy, isn't it true that if you adjust the input gain on a JBL MS amps you may put the onboard DSP input gain beyond digital zero, which is bad for the DSP and creates horrible distortion?

It's not the same as overlapping gains on standard analog amp.


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## Mao123 (Jun 10, 2014)

Hi all, 
I also have a problem with my ms-a1004
I am keeping the stock head unit of toyota priusV
And adding an LOC audio control.
I know both of these units can work as a remote turn On
By using the high level speaker signal coming from the HU
Because im having connected the LOC, how i should set the sensitive turn on on the amp? On or off. And how should i wire power and remotes properly to LOC and amp? Thanks in advance to anyone can help me.


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## theoldguy (Nov 17, 2009)

Mao123 said:


> Hi all,
> I also have a problem with my ms-a1004
> I am keeping the stock head unit of toyota priusV
> And adding an LOC audio control.
> ...


why bother using a line out converter when the amp has one build in?


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## alexmax80 (Sep 6, 2014)

Cant someone help me!
Last weeck i habe bought a jbl ms a5001 and i dont have the setup cd!
Can someone help me with a cd upload?


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## fahadco80 (Mar 19, 2015)

Andy Wehmeyer said:


> Check the crossover on the amplifier. Make sure that the HP filter on the sub channels reads "off" and the LP filter on those channels reads something like "80".



Hi,

May I know how can I set my MS-A1004 to 2v, cause this is the preferred settings for the MS-A1004 while connected to the MS8, but I really do not know how to set that up, I read a lot that it has to be to set at 2v but know one is explaining exactly how to do that, FordEscape (member) told me to turn the dial to full CCW while the amp switched off, but which dial and how it will work while switched off? is it the big silver dial in the middle (on top) or the small black level on the back that I turn with screwdriver?

Do I have to press the left small silver button while turning the big silver button in the middle to CCW?

Sorry but I am really confused.

Please help

Thanks

Fahad


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