# speaker level output to rca input



## bbotelhoHI (Mar 7, 2011)

is that even possible without the use of a LOC?

theres a guy on another forum that insists that he will be able to just cut his RCA cables and wire them inline with the speaker outputs to add an amp to his factory head unit. im telling him otherwise. i know the voltage isnt really a concern, but the impedance is, right? what do the audio gurus have to say?


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## Timelessr1 (Feb 12, 2010)

Actually the other guy is right. Impedance isnt determined by the amplifier...in this senerio the stock headunit,, its determined by the speakers it runs. Some amplifiers can actually accept a high voltage as their preamp input such as the JL Slash series amps. You could splice an RCA end right into your highlevel Radio signals and put it straight into the amps preamp inputs with out LOCs


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## SoulFly (Mar 15, 2011)

Timelessr1 said:


> Actually the other guy is right. Impedance isnt determined by the amplifier...in this senerio the stock headunit,, its determined by the speakers it runs. Some amplifiers can actually accept a high voltage as their preamp input such as the JL Slash series amps. You could splice an RCA end right into your highlevel Radio signals and put it straight into the amps preamp inputs with out LOCs


yeah, they usually have a high/low switch. my mtx elite has the same thing as well as my slash as you mentioned. i prefer a LOC with 8-10v output but thats me.


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## bbotelhoHI (Mar 7, 2011)

hmmm... from what i understood, the issue was with the current that is seen by the amplifier at their input, and not the voltage. 

it was my understanding that the gain on the amplifier is used to match the input voltage (low or high) to have proper signal output levels to the speakers.

i also dont know what type of amp he is running or if it has a selectable hi-lo input at the RCA. so is this an issue of current or voltage?


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## TrickyRicky (Apr 5, 2009)

Some amps do have "hi" input instead of RCA's. To name one JBL BP1200.1 had them (also other JBL BP models). Then there are some linedrivers or crossovers that accept hi-lever inputs (controlaudio has a few).

But splicing it and hooking it up to the amp, I would assume you would have the gain all the way counter clockwise. But then again, i've never tried this.


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## Chaos (Oct 27, 2005)

It is entirely possible to adapt *some* OEM speaker level outputs directly into the RCA inputs on *some* aftermarket amplifiers. It depends on how much voltage the OEM source provides, and the input sensitivity range of the aftermarket amp.

Heck, just one example of this process is printed right in JL Audio manuals, but still nobody seems to believe this.


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## PaulD (Nov 16, 2006)

bbotelhoHI said:


> hmmm... from what i understood, the issue was with the current that is seen by the amplifier at their input, and not the voltage.
> 
> it was my understanding that the gain on the amplifier is used to match the input voltage (low or high) to have proper signal output levels to the speakers.
> 
> i also dont know what type of amp he is running or if it has a selectable hi-lo input at the RCA. so is this an issue of current or voltage?



Amplifiers inputs are voltage sensing, not current sensing. This is why you can use Y cables almost indefinitely on the inputs.

An LOC is an easy $50 for a shop, so of COURSE you need one.


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## sqshoestring (Jun 19, 2007)

It depends on the amp. I have some MTX JH that sense it and even come with RCA plugs with regular wires on them, the amp has no high input you use those, and no switch it senses it. Most amps have a speaker level plug with wires. Some old amps could do it like linear power they could take 5v speaker level input off the old low power HU, that is why their PA2 was a 5v line driver and worked great. Many old amps would not take that kind of input and were for 2v RCA HU at most. New amps tend to take more input with all the higher voltage HU and line drivers out there. Also just because it will work does not mean its the best way to go. HU high power speaker negatives can float at 6v that means the RCA shield will do the same, while old (maybe ancient) HU the negative speaker was ground (3 wires). As a rule I never would hook something up this way unless the particular amp said to do it, only then I would try it.

The issue would be too high a voltage for the amp's preamp input to handle (a LOC cuts this down, or can), or possible noise issues due to how the RCA is shielded and connected in the amp. Different amps use different circuits in the preamp section to handle noise/etc.


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## TrickyRicky (Apr 5, 2009)

Chaos said:


> It is entirely possible to adapt *some* OEM speaker level outputs directly into the RCA inputs on *some* aftermarket amplifiers. It depends on how much voltage the OEM source provides, and the input sensitivity range of the aftermarket amp.
> 
> Heck, just one example of this process is printed right in JL Audio manuals, *but still nobody seems to believe this*.


Same with wiring SVC subs in series. They say "NO DONT DO IT, your wrong, your going to mess up your amps and subs". But back in the day when you didnt have DVC or multiple voice coils, you could wire two single voice coil subs series and it would actually make amps sound better (since increasing dependance).


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## SoulFly (Mar 15, 2011)

If you wire speaker level outs to an amp that does not support high level it usually has a very loud pop when turned on and sounds like the gains are wAy too high, basically sou ds like crap. It can damage the amp, all amps are different but that's been my experience with such attempts in the past...just get a LOC and be done with it.
With high level inputs on amps, I think it's better not to use them, usually get better SN and less distortion with a quality LOC


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## bbotelhoHI (Mar 7, 2011)

thanks for all the replies guys! learn something new every day on this site  the whole time i thought the problem would be due to the fact that the signals from the speaker wire would have too high or too low a load to be used properly in his application. mahalo for the correction!

it still looks like the responses are mixed regarding the cutting and splicing. if it were me, i know what route i would go. especially since the dude said his amp can only accept from 100mV to 4V inputs


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## Chaos (Oct 27, 2005)

PaulD said:


> Amplifiers inputs are voltage sensing, not current sensing. This is why you can use Y cables almost indefinitely on the inputs.
> 
> An LOC is an easy $50 for a shop, so of COURSE you need one.



At least somebody gets it 




SoulFly said:


> If you wire speaker level outs to an amp that does not support high level it usually has a very loud pop when turned on and sounds like the gains are wAy too high, basically sou ds like crap. It can damage the amp, all amps are different but that's been my experience with such attempts in the past...just get a LOC and be done with it.
> With high level inputs on amps, I think it's better not to use them, usually get better SN and less distortion with a quality LOC


Yes & No. Like I said, it really depends on the specific equipment you are trying to integrate, and where you are tapping into the OEM signal. Sometimes the end result sounds better one way than the other, but I don't think I've ever seen an amp actually be damaged by high-level inputs.


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## IBcivic (Jan 6, 2009)

From my past experiments, it can be done, but most of the time you end up with hiss and/or a highly sensitive volume button (since the signal is already amplified, therefore the aftermarket amp's input saturates very quickly) MHO...I'd use a good quality loc or signal processor.


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## Shane oh (Feb 18, 2021)

Just purchased my first Android HU
With lots of gadgetry and some substantial speed and memory. Also a DSP on board. I was surprised to find that the RCA outputs were just spliced into speaker wires with a shared ground intricately weaved to each . The ground derives from the single sub output which is not showing the same output voltage as the fronts and rears. They are 3V higher than the sub output . 5v to 6v = 2v to 3v on sub .. we'll have to see what happens


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## dumdum (Feb 27, 2007)

Shane oh said:


> Just purchased my first Android HU
> With lots of gadgetry and some substantial speed and memory. Also a DSP on board. I was surprised to find that the RCA outputs were just spliced into speaker wires with a shared ground intricately weaved to each . The ground derives from the single sub output which is not showing the same output voltage as the fronts and rears. They are 3V higher than the sub output . 5v to 6v = 2v to 3v on sub .. we'll have to see what happens


Is it thread from the dead day? It’s ten yrs old 🙈


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