# Low level Input VS High Level Input on SQ



## Nick337 (Nov 19, 2009)

I have a question not sure if its been asked before. Whats the difference in SQ in Low level inputs vs High level inputs on SQ. I'm asking in regards to All my Jl audio Amps. Thanks for your help.


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## MarkZ (Dec 5, 2005)

Not much, if done properly. As far as the amp is concerned, it should do equally well with either one. The main variable is the head unit. You need to make sure that the high level OUTPUT of your HU is clean and isn't clipping if you're going to pull this off.


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## Nick337 (Nov 19, 2009)

The signal going to the amps is processed by the bitone.1. Thanks for your help. I appreciate it. It "sounded" like it would perform different whenever i switched it from high to low.


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## jimmy154 (Jul 26, 2009)

Harmony Central - Balanced Vs. Unbalanced I/O


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## DaveRulz (Jun 22, 2006)

The switch on the amp basically attenuates the RCA inputs so that you don't over-drive the amplifier's input stage if using a hotter signal (IE those from the speaker outputs on your HU). 

Flipping the switch to high level should make the overall output lower if all else stays the same.

Remember, the gain control is used to match the incoming signal to the capabilities of the pre-amp section. This switch allows a larger signal (ie: from the speaker outputs of your HU) to be used as well as a preamp level signal.

It should be said that some stock HU's have horrendous amplifiers in them that add lots of noise and distortion to the signal. Whenever possible, you should avoid using speaker level inputs on an amplifier in favor of using the preamp outputs from your HU.

Which would you rather?
HU Preamp -> HU amplifier -> Line output converter -> amp
HU Preamp -> amp

Also, that link above isn't working, but we're not talking about balanced vs unbalanced, totally different concept


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## jimmy154 (Jul 26, 2009)

Oh yes sorry, I just assumed the low level were unbalanced and the high level were balanced.


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## chad (Jun 30, 2005)

It was kinda worth posting the link because JL DOES indeed have differential inputs disguised as RCA connectors.


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## MarkZ (Dec 5, 2005)

DaveRulz said:


> Which would you rather?
> HU Preamp -> HU amplifier -> Line output converter -> amp
> HU Preamp -> amp


But it's not that. It's...

HU amplifier -> amp

vs.

HU pre-amplifier -> amp

Same number of stages. The only difference is that in one case the HU is sending its signal to a power amplifier inside the HU and in the other case it's just a voltage amplifier. Sometimes there isn't a big difference between the two when you measure them.


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## DaveRulz (Jun 22, 2006)

Learn something new every day. Makes complete sense, and I've never tested it, just going off what I read (keyboard commando? oh no!)

That being said can you elaborate on this for me as I'm sure you've got more info on this than I do

What's the difference between flipping the input range selector on the JL amp and installing your run-of-the-mill LOC (other than the LOC requires extra wiring splices)? I'd imagine the basic method of knocking the hotter signal down is the same/similar between the two.

My basic understanding was that it's pointless to ramp the power up (using an amplifier that will introduce distortion), just to knock it back down once it reaches the amp.

I guess the gist of what you were saying is that often the Preamp outputs offer up just as much distortion as the speaker level outputs.


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## Bmxnick101 (Dec 1, 2009)

Being that the JLs have a balanced input, could you possably figure out a way to add a "ground" and make the line level balanced?


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## mosca (Oct 26, 2009)

bump.

I'm interested in this balanced line stuff. I have JL Audio HD's too.

I also have a Bit One which will act as a hub between my stock HU @ speaker level inputs and a CarPC via optical. I searched the manual and the internets to find if the Bit One has balanced inputs/outputs but the result was nil.

I think another thing to take into account regarding the speaker level inputs is the possible dynamic equalization, which would have to be corrected. wouldn't this take some quality points from taking this path VS RCAs?


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## t3sn4f2 (Jan 3, 2007)

mosca said:


> bump.
> 
> I'm interested in this balanced line stuff. I have JL Audio HD's too.
> 
> ...


The bit one has unbalanced single ended outputs. In order for it to be balanced out it would need three wires, the +, -, and ground. They would not put those since the amp connected to them would have to have balanced inputs or differential-balanced like your amps and not all of them do.

I'm not sure about the RCA inputs but they are more then likely differential-balanced inputs like on your HD amps. Diff-balanced can accept single ended, balanced (the + and - wires, leave the ground wire floating at the bit one side), and speaker level as well.


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## mosca (Oct 26, 2009)

t3sn4f2 said:


> The bit one has unbalanced single ended outputs. In order for it to be balanced out it would need three wires, the +, -, and ground. They would not put those since the amp connected to them would have to have balanced inputs or differential-balanced like your amps and not all of them do.
> 
> I'm not sure about the RCA inputs but they are more then likely differential-balanced inputs like on your HD amps. Diff-balanced can accept single ended, balanced (the + and - wires, leave the ground wire floating at the bit one side), and speaker level as well.


thanks *t3sn4f2*. but dammit Audison!

so, following this logic, then HUs that have balanced ouputs only can be connected to balanced (or diff-balanced) amps?


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## t3sn4f2 (Jan 3, 2007)

mosca said:


> thanks *t3sn4f2*. but dammit Audison!
> 
> so, following this logic, then HUs that have balanced ouputs only can be connected to balanced (or diff-balanced) amps?


Exactly, you can also use a high quality transformer  in between the two types.


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## chad (Jun 30, 2005)

t3sn4f2 said:


> The bit one has unbalanced single ended outputs. In order for it to be balanced out it would need three wires, the +, -, and ground. They would not put those since the amp connected to them would have to have balanced inputs or differential-balanced like your amps and not all of them do.


Don't need ground, 2 wire balanced has been around forever and it's probably in your house... it's in my house, studio and car. My shields are screens and not attached at one end


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## t3sn4f2 (Jan 3, 2007)

chad said:


> Don't need ground, 2 wire balanced has been around forever and it's probably in your house... it's in my house, studio and car. My shields are screens and not attached at one end


ooppss I meant three connections, third one being for the shield? I have a feeling not even for that though since I've heard people recommend to ground to the source chassis instead of the third wire on the balanced output.


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## mosca (Oct 26, 2009)

I've found some info on balanced line drivers @ BCAE1 Balanced Line Drivers

tomorrow maybe I will ask you some questions regarding your replies, guys. now I need some :cwm33:


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## chad (Jun 30, 2005)

t3sn4f2 said:


> ooppss I meant three connections, third one being for the shield? I have a feeling not even for that though since I've heard people recommend to ground to the source chassis instead of the third wire on the balanced output.


there are 3, especially for apps requiring phantom powering, it's common practice to lift the shield at the receiving end so it cannot develop current.

Telco is UTP single pair balanced, so is your internets out of the router/modem.


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## mosca (Oct 26, 2009)

so, how come that the JL amp can accept both signals (diff balanced / not) but the Bit One can only work with one? it would seem to me that the Bit One, being "high end" would be as smart as the JL. or it is just not possible with an output signal?


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## mosca (Oct 26, 2009)

from the JL Audio page:



> Unlike conventional single-ended inputs, the differential-balanced design does not connect one side of the audio signal to chassis ground. This eliminates any voltage sensitivity between one input terminal and ground and greatly reduces the incidence of alternator whine in a typical car audio installation.


would this mean that even that if the full system is not diff-balanced the risk of induced noise is minimized?


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## mosca (Oct 26, 2009)

after reading the BCAE1 article on balanced line drivers I'm still confused. he seems to say that you can have a 2 points RCA work diff-balanced, because every device will get its own ground signal (I deduce, or am I wrong?), but then he gets to HUs, and he says this:



> The output of the balanced line driver is a balanced signal. Some head units also have a balanced output signal. I added this section for those who may want a little more information specifically related to head units. The diagram below shows the signal output configuration of a head unit with unbalanced outputs. The signal is on the center terminal of the RCA cable and the shield is connected to the chassis ground of the head unit.
> 
> 
> 
> ...


what does he mean by "using a switch or a different set of cables"?


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## t3sn4f2 (Jan 3, 2007)

mosca said:


> so, how come that the JL amp can accept both signals (diff balanced / not) but the Bit One can only work with one? it would seem to me that the Bit One, being "high end" would be as smart as the JL. or it is just not possible with an output signal?


Are you asking why can't the bit one _output_ balanced when the jl and the bitone can accept bal/unbal (assuming here that the bit one can since other processors can)?


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## chad (Jun 30, 2005)

Balanced inputs can work unbalanced without issue, balanced inputs can work fully balanced without an inverting signal as long as the inverting section's input has the same impedance characteristics as the non inverting. remember it's not balanced audio like the marketing department thinks, it's balanced impedance.


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## mosca (Oct 26, 2009)

t3sn4f2 said:


> Are you asking why can't the bit one _output_ balanced when the jl and the bitone can accept bal/unbal (assuming here that the bit one can since other processors can)?


yes, but more in a sense that why it cannot output both.

but I also ask (though not explicitely) if RCAs need to be balanced or unbalanced, because that is what BCAE1 doesn't state clearly enough, for me at least. I mean, it talks about ground, but I can not see where this ground comes from (I might have an obtuse morning, BTW). does each device get it from its own ground connection? meaning this that it is not passed through the RCA cable?

also, if a balanced input can accept unbalanced input (well, both), is it not posible the inverse? now that I think about it it makes sense, since we would be sending positive signal where the ground should be?


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## mosca (Oct 26, 2009)

chad said:


> Balanced inputs can work unbalanced without issue, balanced inputs can work fully balanced without an inverting signal as long as the inverting section's input has the same impedance characteristics as the non inverting. remember it's not balanced audio like the marketing department thinks, it's balanced impedance.


okay I understand this part now.


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## chad (Jun 30, 2005)

mosca said:


> okay I understand this part now.


now given that, if oyu can mock the output IMPEDANCE characteristics of the pin (driven) with the ground (sleeve) of the output of your bit one you can run impedance balanced.


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## mosca (Oct 26, 2009)

chad said:


> now given that, if oyu can mock the output IMPEDANCE characteristics of the pin (driven) with the ground (sleeve) of the output of your bit one you can run impedance balanced.


damn it's getting harder 

I *think* I'm understanding it, but I will have to let this settle a bit so I can get the final click.


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