High-Level Input Vs Low-Level Input (RCA)
At first glance, high-level inputs, and low-level inputs, also famously known as RCA inputs, may appear identical, especially for a first-time user. Ideally, the two sets of inputs are found at the back panel of a subwoofer, and they are used to add an aftermarket amplifier to any sound setup.
When looking to add a new amplifier to your stock stereo system, finding a way to integrate the amp is often a big consideration. So, what’s the difference between high-level input vs low-level input? In this article, we’ll highlight primary differences between the two inputs and show which set to use for what application.
In a nutshell, the primary difference between high-level and low-level inputs is the type of audio signal transmitted through each input. The high-level input, or simply speaker level input, helps to transmit audio signals using speaker connections from the amplifier to your subwoofer.
On the other hand, low-level (RCA) input facilitates the transmission of low-level audio from your amplifier to the LFE (subwoofer) unit. That said, let’s dig deeper into these audio terms to keep you informed on their noteworthy features and the differences between the amp high-level input vs RCA.
What is high-level input on amp?
The primary role of high-level inputs is to allow the user to add an amplifier to either a stock or aftermarket stereo that does not include RCA (low-level) connectors. Ideally, high-level inputs are characterized by several speaker wires that plug into a multi-pin wiring harness.
In other words, the speaker level inputs allow you to connect almost any amplifier to your sound system without the need to use an additional level-matching device. Such amplifiers will often come with a special adapter featuring bare wires that you’ll use to connect to the speaker wires. That way, the amplifier is able to utilize the speaker output signal as its input source.
Overview of low-level input (RCA)
Low-level inputs, or simply RCA/line-level inputs, are a type of connectors used to integrate an amplifier that is not compatible with high-level inputs or when the inputs are unavailable. In such applications, you’ll need to utilize the designated RCA interconnect cable to connect the amplifier to your source device.
The best thing about aftermarket stereos is that they are equipped with several RCA inputs that you can use to add multiple amplifiers. However, it is important to highlight that RCA inputs are often used with aftermarket setups that mostly lack speaker-level inputs.
High-level input vs RCA- The Key Differences
Perhaps the most notable difference between subwoofer high-level input and RCA input is the kind of connectors they use. As we mentioned earlier, the high-level inputs come in a series of identical speaker wires that plugs into a multi-pin wiring harness.
On the other hand, low-level inputs are color-coded, with each color representing each channel of your stereo system. In addition, the inputs feature a color-coded opening coupled with a metallic lining on the inside part of the hole.
Typical scenarios that require one to use low level inputs in place of the speaker level inputs include;
- Applications that do not permit the user to use speaker outputs. For example, the RCA inputs are your to-go option when connecting to a computer or TV directly.
- Using the low-level inputs is the most preferred method when connecting Monoblock amplifiers with a single REL. Such applications require you to use a pair of stereo connectors for both the left and right channels,
When it comes to functionality, the high-level inputs are responsible for the transfer of signal from your amp or even receiver to the subwoofer unit. Typically, the transmission of signals is facilitated by speaker-level connectors found at the back panel of your subwoofer.
Similarly, low-level inputs help to transmit audio signals between your amp/receiver and the sub but instead of using speaker outputs, the latter uses the RCA connectors. Generally, most AV receivers and aftermarket amplifiers use the RCA inputs to transmit audio signals via preamps outputs.
Another notable difference between low-level vs high-level amp input is the level of voltage. Ideally, the low-level, inputs just as the name suggests, accommodate low-voltage signals to the amp/receive, where the signal is amplified.
During transmission, the audio signal may not be powerful enough to push your subwoofer/speakers. Once in the amplifier, the signal is amplified, hence allowing you to enjoy the audible sound. On the flip side, the signal transmitted by the high-level input is often powerful enough to run the subwoofer.
In terms of the sound produced, there seems to be no noticeable difference in sound quality, especially when using an aftermarket stereo system. However, the high-level signal tends to suffer a bit when using a stock stereo system as opposed to when running the signal through low-level inputs.
This is because the user is required to tap into existing vehicle wiring, and in the process, it might cause signal degradation. Other than that, both input methods are highly flexible, and you can use either to install your new system depending on your application needs.
Older receiver models without high-level inputs may also use low-level inputs in place of the speaker-level inputs. As such, when looking to add a subwoofer or amplifier to your setup, you may want to counter-check the available set of inputs and outputs. This will help you avoid incurring additional repair costs or the need to buy new wires/adapters to go with your new setup.
The good thing is that most, if not all modern subs, are equipped with both sets of inputs. In the past, RCA inputs were quite rare, but today it is not uncommon to find most subwoofers with several RCA inputs. This helps ensure you won’t run into a problem, especially when you want to use both types of inputs.
Using the right inputs allows you to get the most out of your audio system. However, the type of cable and inputs you use can make or break the sound you get from your system. The subwoofer only constitutes half of your sound experience, but to get the most from your entertainment setup, you’ll need to get it right when it comes to plugging the cables into the correct inputs. Furthermore using the right connectors and inputs allows your music and movie sound effects to come to life.
Necessary to use all high level speaker input wires?
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Aftermarket amp input wire has 4 pairs total for the fronts and the rears. Am I required to tap into all 4 speakers to add a sub or can I pick and choose a single speaker to tap into and ignore the rest?
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You need to know if that channel has sub information or if it’s cut out by the factory headunit. What kind of vehicle and trim level? Regardless I’d take both left and right to sum together into a mono bass signal.
Its a 1st gen tlx. It does have a factory subwoofer. So do I tee off of the rear left and right speaker? Or use the single pair coming off the sub? Or all 3 speakers?
I’m also curious why there’s a whole set of input wires but unnecessary to use them all. Is the purpose just for signal if 1 or 2 pairs isn’t enough signal or how does that work?
Note, I am not experienced with that car. But if you have a factory sub that seems like the first place to check. Do you have any measurement tools that can check the signal into the amp?
Am amp has multiple inputs for separate channels. You could run:
Left and right for both front and rear
Left and right tweeter and mids
Left and right front passive set plus bridged channels to a sub
Many combinations are possible. What’s your goal and what equipment do you already have?
I only have the basics: sub, amp, and wires. Only tool I have that might be useful is a DMM.
All I want is to add a sub that isn’t 8″ and 40 watts like the factory.
There are a handful people reporting running a passive LOC and only wired to the factory sub with good results. On paper there should be some bass drop which I’ve only read 1 person come across so I think it exists to an extent.
I’m going straight to an amp so I don’t know what my results would be and whether I should make use of all the input wires or only the ones I need. Says “4 channel speaker level inputs” so 4 Lefts and 4 Rights.
Since I have access to the rear sub and 2 speakers beside it, could I connect those to the input wires? Use RL RR and FL wire coming from the input maybe? Let me know your thoughts thanks. Also sorry for the wall of text.
What model are the amp and subwoofer?
Amp: Alpine MRV-M500
Sub: 12″ Skar SDR 600rms
Guess it’s my turn for the wall of text.
Regarding the sub wiring, did you buy the dual 4 Ohm version of that Skar sub? If so then you can parallel the voicecoils into a 2 Ohm mono load which will maximize the power from that amp. You can parallel either at the amp or subs speaker terminals. The larger amp terminals are likely easier. If you bought the dual 2 Ohm version then you’ll need to series connect into a 4 Ohm final load.
As for the amp input, your amp’s manual states, “MRV-M500/MRV-F300 accepts input from high power or standard power head units.”
There is a note for using both L&R channels of an input, “Low output will result if only one channel input is used. The Y-adapter is not required if a stereo/mono pair line output is used to drive both inputs of the bridged amp. ” Also,
“Only left/right channel speaker level input is required. However, all speaker input leads (FL/FR/RL/RR) may be connected to prevent zero output when the head unit fader is adjusted”
You could tap into the factory sub before the amp, if possible. This is possibly already crossed over by the factory system. Someone else might know this vehicle but, as stated above, I do not. You can find out if it is crossed over or not with your DMM. Disconnect the factory sub where you are looking to tap. Set the DMM to read AC Voltage and connect to that tap point. Play bass tones and watch/record the voltage level. If they are all the same voltage level between 20-100 Hz then you have a flat output signal from your headunit. You will use your new Alpine amp’s crossover feature to control the low-pass frequency. If the voltage readings fluctuate (drop off at high or low frequencies in the sub range) then your headunit is already filtering the signal (more likely). You can use that signal as-is and open up the crossover setting on the amp or look for a full-range signal in the car for more control of the subwoofer crossover frequency. You would repeat this experiment on your other speaker leads and look for a full-range signal. I would prefer to have more control but the extra work is up to you since it’s your system. Regardless, set the gains correctly. Do not just wing it or guess.
Do note for future reference, “Use either RCA line level or speaker level inputs. Do not connect both at the same time.”
FYI regarding the remote turn-on, your amp’s manual has this note: “If using speaker input level signal from the head unit, remote turn-on lead connection is not necessary due to automatic signal detection.” Also,
“For the “Speaker Level Input System” setting, connecting the Remote Turn-On Lead is not required due to the “REMOTE SENSING” function of this product. However, the “REMOTE SENSING” function may not work depending on the signal source connected. In such a case, connect the Remote Turn-On Lead to an incoming power supply cord (accessory power) in the ACC position.” And lastly,
“Remote Turn-On Lead
a. The head unit does not have a remote turn-on or power antenna lead.
b. The head unit’s power antenna lead is activated only when the radio is on (turns off in the tape or CD Mode).
c. The head unit’s power antenna lead is logic level output (+) 5V, negative trigger (grounding type), or cannot sustain (+) 12V when connected to other equipment in addition to the vehicle’s power antenna.
If any of the above conditions exist, the remote turn-on lead of your MRV-M500/MRV-F300 must be connected to a switched power source (ignition) in the vehicle. Be sure to use a 3A fuse as close as possible to this ignition tap. Using this connection method, the MRV-M500/MRV-F300 will turn on and stay on as long as the ignition switch is on.”
So I spent the weekend rigging quick temp setup and the bass does seem to get flat once I really turn up the volume yet the other speakers get louder. Line output only wired to sub only so I wonder if wiring another pair to one of the regular speakers would help with this. Or my only option is lc2i?
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Do-it-yourself high-level amplifier input
Choosing an amplifier today is a rather complicated process that requires a careful approach. But no less important is the issue of connecting the selected amplifier to your head unit (car radio). In this article, we will try to deal with the most common methods, possibilities and difficulties of connection.
Theoretically, the amplifier can be connected to any type of car radio: either purchased separately or built-in by the manufacturer (standard). It would seem, “what difference can there be in connecting, even if their brands can be the same?”. And there is a difference, and a significant one.
According to statistics, it is much easier to connect to a self-purchased car radio, since regular radios cause many difficulties. The reason for this situation is that most car radios built by the manufacturer do not have an audio processor, which is responsible for the process of transmitting an audio signal from the radio to the amplifier. In this case, the way out of this situation can be the use of high-level inputs, more detailed information about which will be presented below.
One of the common problems with connecting an amplifier to the head unit is the presence of interference in the transmission of an audio signal
. This is related to the transmission distance (from the front to the rear of the cabin). In this case, it is very convenient to use a balanced audio signal transmission scheme, the possibility of which is supported by individual amplifier models. A “bright” representative of the use of a balance transmission system (ABS), moreover, of its own design, are Audison amplifiers.
So, let’s take a closer look at the process of connecting the amplifier to the car radio. Theoretically, the process is not difficult. The connection is made using special linear connectors of the “tulip” type (RCA): “radio audio outputs + amplifier audio inputs”. The main task is the correct selection of the appropriate channels and the length of the connecting cable. The problem may appear when the number of linear-type outputs of the head unit and the amplifier inputs do not match. Most often, the discrepancy is associated with a lack of car radio outputs, which is corrected by using a special input selector. The purpose of this component is to double the channels of the input signal. It is available in almost all modern multi-channel amplifiers. The described connection method is suitable for all purchased car radios.
But what about connecting an amplifier if you have a head unit? Naturally, the process will be more complicated due to the lack of linear outputs, but it is quite possible. At the same time, the methods differ from each other both in complexity and cost of inclusion, and in sound quality.
Serkey › Blog › Connecting the amplifier to the standard head unit
Connecting the amplifier to the standard head unit
Let’s start simple. In a car audio system, connecting an external power amplifier to a separately purchased signal source – be it a CD receiver, a multimedia station, a media receiver, or something else that continues to be called a “radio” out of habit – does not cause any difficulties. To do this, use the line-level audio outputs (i.e., designed to transmit a line-level signal) on the signal source represented by RCA connectors and, accordingly, the audio inputs on the amplifier. So, you will only have to attend to related tasks, namely, the choice of an interconnect (interconnect) cable with RCA connectors that is appropriate in quality, number of channels and length. The only hitch may arise if the number of line outputs on the signal source is less than the number of inputs needed on one or more amplifiers in the audio system. For example, on a source there may be one pair of them (i. e. left and right channels of a stereo pair), and on a 4-channel amplifier there may be two pairs (one pair for the front channels, and the second for the rear, or subwoofer channel operating with the sum two channels). The hitch is easily resolved using the input selector, which is equipped with the vast majority of modern amplifiers with more than two channels – this function serves to repeat the input signal for those channels that “got it”. If in the same situation there are two or even more amplifiers, then the linear outputs of the amplifiers come to the rescue – not every model on the market has them; nevertheless, appear in equipment very often. The signal from such line outputs either exactly repeats the input, or is passed through the sound control circuits of the amplifier – say, through a crossover.
Much more intricate operations await when connecting an amplifier to a standard head unit – and this is exactly what happens with modern cars most often. It’s no secret that regular “receiver” is not initially adapted for this: they do not have linear audio outputs. Nevertheless, the task is always solvable: there are many ways to do this, differing both in sound quality and in the complexity and high cost of practical implementation.
Connection via high level inputs
This is the easiest and, as a result, extremely popular connection method. The signal from the head unit is fed to the amplifier input, which was originally intended not for the amplifier, but for the speakers – i.e. already past amplification in a not too high-quality and flimsy built-in amplifier of the head unit. For comparison: the magnitude of the linear level signal is several volts (typical value is 1-2 V, for high-class sources it reaches 4-5 W, occasionally up to 8 V), and the high-level signal from a regular source exceeds a dozen, or even two ten volts – hence it got its name. To implement such a connection, the amplifier must have the appropriate equipment – high-level inputs. Not every model has them, but in the latest generations of the junior / middle, and sometimes high-end, many manufacturers often have them.
The same is the case with the connection of active cabinet subwoofers, whose built-in power amplifier is completely identical to the individual external amplifiers in terms of the switching method. The only difference is that active subwoofers with high-level inputs are much more common (in fact, the probability of finding such equipment in them is close to 100%) than external amplifiers. In addition, to simplify the installation in the configuration of subwoofers, you can often find a ready-made power supply cable of the desired cross section and length, with a fuse, or even with a set of cables for transmitting an audio signal.
Loss of sound quality with high-level connections is often a source of criticism, but it’s worth looking into – how significant is it? If we are talking about the first “adult” audio system, with younger versions of amplifiers and speakers of the corresponding level, then the disadvantages of high-level connection are easy to forgive. If the stock system is upgraded by just adding a subwoofer to improve bass, then the difference in connection methods turns out to be negligible at all – the result will be the sound quality of the main speakers, and in this case it remains unchanged. Another thing is high-level audio systems for a sophisticated audience. There, the sound flaws due to the presence of irreparable distortions will already be much more noticeable and will force you to look for an alternative way to supply a cleaner audio signal by all means. Let’s not forget that the higher the class of technology, the higher its resolution – in other words, the more it shows not only the advantages of sound, but also its shortcomings. For example, those flaws that literally “cut the ear” in the speakers for EUR 500 may not be too annoying in the speakers for EUR 100. And one more thing – the standard head unit in any case remains a compromise and forced signal source, no matter in what form it is it was not received: at least for linear outputs, at least for high-level ones. Neither in the mechanical stuffing, nor in the digital section, nor in the pre-amplification section of a regular source is there anything close to the audiophile concept, and cannot be. So choosing among the linear and high-level options is still “two evils”, and at the initial level the second one often wins due to its much greater simplicity and cheapness.
From the above, we can make an erroneous conclusion that the presence of high-level inputs at the amplifier is evidence of its low class and inability to sound interesting for a sophisticated audience. This is not so: there are truly wonderful and not at all cheap amplifiers designed for high-end audio systems with top-class purchased signal sources, but equipped “just in case” (or rather, a forced case) also with high-level inputs.
Moreover, the lack of high-level inputs on the amplifier does not exclude the possibility of signaling in this way. There are a large number of additional external accessories that convert a high-level signal to a linear one, they are very compact (sometimes the size of a matchbox) and very inexpensive. But despite the utility of the task, in this case, as always, it is better to opt for products from manufacturers with a good reputation.
In addition to the lack of line outputs, regular head units present another unpleasant surprise: as a rule, they do not have a special connector for transferring the on / off control of an external signal amplifier. To get around this limitation, modern amplifiers are often able to detect the presence of a signal at the inputs (some only at high levels, some also at linear ones) and automatically turn on when it is detected. However, not all of these circuits work correctly, sometimes leading to an erroneous shutdown of the amplifier if the input signal is too weak. Let’s say you come across a pianissimo fragment in a classical piece, but the sound disappears. For amplifiers with reputable tracking circuits for the input signal, you can not be afraid of such a nuisance.
Connection via line input
The second way to connect the amplifier to the standard car radio is using audio line outputs
. The line signal does not require a special creation process, but is initially present in the system, you only need to extract it correctly, which can be easily done in any installation center. This option avoids the disadvantages of high-level connectivity. The problem is that the possibility of such a connection does not exist in all systems: the car radio may be too rare a model or simply too difficult to study.
Another problem is the need for direct intervention in the car’s electronics during the installation of the amplifier. With the smallest error, a violation of the adequate operation of the on-board electronics is likely, in connection with which, issues of car warranty service may also arise. Therefore, if you, nevertheless, settled on this connection option, initially protect yourself from troubles of this kind and, nevertheless, contact an experienced installer in a specialized center.
Volkswagen Jetta 159 › Logbook › Subwoofer and amplifier with high-level input
After buying the car, I was very surprised that there were not only speakers in the rear doors, but even preparation! In the comfortline configuration, audio preparation is made up to the middle pillars. When buying an RCD 510, I got a set of standard speakers from another Jetta for free, which were installed in the rear doors.
After changing RCD 510 to RNS 510, I decided to install a subwoofer, hoping that there is an output for a subwoofer. But alas, all hopes were in vain – ITS NOT! I came to the acoustics store, the seller turned out to be an adequate person and who knows his business. I explained the situation and he offered this kit: Power amplifier Art Sound JAB 120.2 Gray
Subwoofer Kicker C124
Output power / per channel (2 ohms) 160 W Output power / per channel (4 ohms) 120 W output power / bridge ( 4Ω) 320 W Frequency range 20 – 30000 Hz Operation class AB Number/value of fuses 2 x 25 A Number of amplification channels 2 Harmonic distortion ratio 0.2 % S/N ratio 90 dB Stable operation into a load of 2.4 Ω High filter cutoff frequency 50 — 250 Hz Low-pass cutoff frequency 50 — 250 Hz
High Level Input
Line Input Sensitivity 0.25V – 6V Bridged Built-in Bass Boost Circuit Built-in HPF, LPF Bass Boost Level 12dB Bass Boost Frequency 40Hz Having a high level input was the reason for buying it as there is no output on the tape recorder.
Connection via processor-restorer
The third option for connecting the standard car radio is used in the absence of linear and high-level signals. In this case, it is necessary to connect a special device – recovery processor
, which connects the cut pieces of frequencies. This device is multifunctional and, among other things, removes distortion and restores the low-frequency register (bass). Naturally, the quality of such restoration cannot be compared with the purity of the sound signal from a Hi-end class source, but in the absence of another connection option, the use of a restorer processor is quite suitable. Due to the widespread use of regular car radios, the demand for this device has increased significantly, there was even a division into classes. In connection with the current market situation, the choice of device should be taken seriously, which will allow you to get a cleaner, “musical” sound.
Of particular interest is the option of obtaining a pure digital audio signal at the output using an amplifier equipped with a digital-to-analogue converter (DAC). But in practice, this is very difficult to achieve, since digital sound is an unrealistic task for most head unit. We should also consider radios that use a special digital interface – MOST
(Media Oriented Systems Transport). At the moment, they are equipped with about a hundred models of luxury cars. In addition, to build a high-quality audio system, which is very problematic, you need to use an additional device – special MOST-S/PDIF adapters. Such an adapter synchronizes the operation of the amplifier and the head unit. The problem is a strictly limited number of these adapters, which practically does not even affect the level of market supply.
One of the ways to get rid of the shortcomings of factory car radios is to replace them with alternative factory radios from other manufacturers. They are usually identical in design, seats and backlight color, but differ significantly in internal content, technical capabilities, and the number of line outputs. You can get acquainted with the range of regular radio tape recorders and choose a PG for your car here. Head units purchased to replace factory ones have significantly better sound quality, despite the fact that, in fact, they are not audiophile, but multimedia devices. In the case of a digital output, the sound quality is directly proportional to the class of the DAC amplifier.
So, we have considered all the main options and available ways to connect the amplifier to standard and purchased car radios. If none of the proposed options suits you, you can use alternative connection methods. Just a few years ago, only CD receivers and DVD/CD changers acted as an alternative source. But technology does not stand still, but is actively developing, and even now such a source can be: any flash drive, iPod / iPhone or other media player. The choice of alternatives is quite wide. The quality of their sound is often criticized and discussed, but the sound quality when playing lossless formats (ALAC, APE, FLAC, etc. ) suits even the most demanding music lovers. In addition, some amplifier models are additionally equipped with special AUX inputs that allow you to receive signals from peripheral audio equipment with maximum quality. The advantage of an alternative connection option is the ability to place it in the most convenient place in the cabin; control with a remote control or standard buttons.
We hope this review of the most common and affordable options for connecting a power amplifier to a car radio will help you choose the most optimal and profitable option for you. If you have any questions about connecting a car amplifier, and your own knowledge is not enough, please contact our specialists by phone.
We wish you connections “without embarrassment” and true pleasure from the result!!!
4-channel amplifier with high-level input in Stary Oskol: 500 items: free shipping, 27% discount [link]
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