When setting up an audio system, one common question that arises is the difference between phono vs aux inputs. Understanding these differences is essential for achieving the best sound quality, especially if you are connecting a turntable or other audio equipment to your stereo receiver or amplifier. This article will explore the main differences between phono and aux inputs, the role of phono preamps, and how to properly connect your audio gear for optimal performance.
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What is a Phono Input?
A phono input is a specialized audio input designed specifically for turntables or record players. Unlike standard line level inputs, the phono input accommodates the unique characteristics of the phono signal produced by a phono cartridge. Phono inputs accept signals from analog turntables and boost them for proper playback. A turntable produces a PHONO output signal, which is very low in amplitude and requires amplification and equalization before it can be processed by an amplifier or receiver.
The phono input includes a built-in phono preamp or phono stage, which amplifies the signal to line level and applies RIAA equalization. This equalization compensates for the frequency response curve used during vinyl record production, boosting lower frequencies and attenuating higher frequencies to restore the original sound. The voltage level of phono signals is much weaker than line signals, typically ranging from 0.0002 Volt to 0.007 Volt. Without this correction, the audio would sound tinny and unbalanced.
In addition to amplification and equalization, the phono input is designed to handle the specific electrical characteristics of the phono cartridge, including its impedance and capacitance requirements. These factors are crucial for maintaining the fidelity of the audio signal and preventing distortion or loss of detail. Most turntables rely on Moving Magnet (MM) or Moving Coil (MC) cartridges, each with different output levels and loading needs, which the phono input or preamp must accommodate.
Furthermore, the phono input’s design helps reduce noise and interference that can be introduced due to the low-level nature of the phono signal. This is why proper shielding and quality components in the phono stage are important for achieving high sound quality. Whether the phono preamp is built into the amplifier or exists as a separate external unit, it plays a vital role in ensuring that the delicate nuances of vinyl playback are preserved and accurately reproduced by your audio system.
What is an Aux Input?
An aux input, short for auxiliary input, is a more general-purpose audio input found on most stereo systems and audio equipment. It is designed to accept line level signals from various sources such as CD players, tape decks, Bluetooth speakers, and audio interfaces. A standard line output will have a voltage level of 0.316 Volts, which is stronger than a phono signal and does not require additional equalization.
Aux inputs are versatile and can be connected using RCA cables or 3.5mm plugs, making them compatible with a wide range of devices. However, they lack the specialized circuitry needed to handle the low-level phono signal from a turntable.
Because aux inputs expect a line level signal, they are ideal for connecting devices that already output audio at this level. This includes modern digital devices like smartphones, computers, and streaming devices, which often use a 3.5mm headphone jack or RCA outputs to send audio signals to external speakers or amplifiers. The simplicity of the aux input makes it a popular choice for general audio connections, allowing users to easily switch between multiple audio sources without needing specialized equipment.
It is important to note that connecting a turntable directly to an aux input without a phono preamp will not only result in low volume but also a distorted and tinny sound. This happens because the phono signal is both too weak and has a different frequency response curve compared to line level signals. The aux input does not provide the necessary amplification or RIAA equalization to correct this, which is why a phono preamp is essential when using an aux input with a turntable.
Main Differences Between Phono and Aux Inputs
Understanding the distinction between phono and aux inputs is key to setting up your audio system correctly. The primary difference lies in the type of signal each input is designed to handle. A phono input is tailored specifically for the low-level phono signal produced by turntables, which requires amplification and RIAA equalization to restore the original sound quality of vinyl records. This signal is much weaker and has a unique frequency response curve compared to standard audio signals.
On the other hand, an aux input is designed to accept line level signals, which are stronger and standardized across a wide range of audio devices such as CD players, tape decks, and Bluetooth speakers. The aux input does not provide the necessary amplification or equalization for phono signals, so connecting a turntable directly to an aux input without a phono preamp will result in poor sound quality.
Phono inputs typically use RCA connectors, often referred to as phono jacks, and are found on stereo receivers, amplifiers, and some audio interfaces. The aux input is more versatile and can accept various types of connectors, including RCA and 3.5mm plugs, making it compatible with most audio equipment.
Another important difference is the signal voltage level. Phono outputs produce a much weaker signal, generally between 0.0002 Volt and 0.007 Volt, whereas line level outputs connected to aux inputs operate at around 0.316 Volts. This disparity necessitates the use of a phono preamp to boost the phono signal to line level before it can be processed by an aux input.
The Role of the Phono Preamp
A phono preamp, also known as a phono stage, is essential for converting the phono signal into a line level signal suitable for standard audio inputs. The phono preamp adds gain and equalization needed to create a proper audio signal before it is amplified by the speakers. Some turntables come with a built-in preamp, making them compatible with aux inputs or line inputs on modern amplifiers and powered speakers. Entry level turntables often include this feature for user convenience. Additionally, some phono preamps allow switching between Moving Magnet and Moving Coil cartridge types, providing flexibility for different turntable setups.
If your turntable does not have a built-in preamp, you will need a separate phono preamp to connect to an aux input or line level input on your stereo receiver or amplifier. This external preamp performs the necessary amplification and RIAA equalization, ensuring the signal matches the expected frequency response and signal level.
The Role of the Phono Outputs
Phono outputs are the specific audio outputs found on turntables that deliver the raw phono signal generated by the phono cartridge. This signal is characterized by its very low voltage level and unique frequency response, which requires special handling before it can be properly amplified and heard through speakers. The phono output does not provide a line level signal, so it cannot be connected directly to standard aux inputs or line inputs without additional processing.
The phono output signal is typically routed through RCA cables from the turntable to either a phono input on a stereo receiver or an external phono preamp. This preamp amplifies the weak phono signal to line level and applies RIAA equalization to correct the frequency response. Without this step, the audio would sound distorted, with excessive treble and insufficient bass, due to the way vinyl records are cut and mastered.
Turntables without a built-in preamp rely entirely on the phono output to send this unprocessed signal to the next stage in the audio chain. It is essential for users to understand that connecting these phono outputs directly to an aux input will result in poor sound quality. The aux input expects a line level signal, which is much stronger and already equalized, so the mismatch leads to low volume and a thin, tinny sound.
Some modern turntables come equipped with a preamp built into the unit, allowing the phono outputs to deliver a line level signal instead. In these cases, the outputs can be connected directly to an aux input or any line level input on audio equipment, simplifying setup and reducing the need for external components. However, when using a turntable with traditional phono outputs, a separate phono preamp or a receiver with a dedicated phono input is necessary to ensure the signal is properly processed.
Connecting Your Audio Equipment: Phono and Aux Explained
When setting up your audio system, it is important to connect your turntable and other devices to the correct inputs for optimal sound. If your turntable has phono outputs and no built-in preamp, connect it to the phono input on your amplifier or stereo receiver using RCA cables. This connection ensures the phono stage inside the receiver properly processes the signal.
If your turntable has a built-in preamp, you can connect it to an aux input or any line level input, such as a line input or auxiliary input on your amplifier or powered speakers. This setup bypasses the need for a separate phono preamp, simplifying the connection process.
For other audio gear like CD players, tape decks, or Bluetooth speakers, always use the aux input or line input designed for line level signals. Avoid connecting these devices to the phono input to prevent distortion or damage.
Additional Considerations for Audio Quality
Sound quality depends heavily on using the correct input and preamp configuration. Phono inputs and preamps are specifically designed to handle the lower frequencies and delicate signal from vinyl records. They apply the RIAA curve to balance the frequency response, ensuring that both high frequencies and lower frequencies are reproduced accurately. Replacing or upgrading speakers is often more impactful on overall sound quality than other components of the audio chain. Additionally, the quality of the phono cartridge is crucial for sound quality in vinyl playback.
Using better components, such as a high-quality external preamp or an integrated amplifier with a superior phono stage, can significantly enhance the listening experience. Additionally, proper cables, like well-shielded RCA cables, help maintain signal integrity and reduce noise. However, high-end cables do not elevate the performance of an entry-level system. Upgrading main components can provide more benefits than buying high-end cables for entry-level systems. Separate phono preamps generally have better components than built-in preamps, leading to better sound quality.
Conclusion
Understanding the difference between phono vs aux inputs is crucial when connecting audio equipment to your stereo system. Use the phono input for turntables without a built-in preamp to ensure the phono signal is correctly amplified and equalized. For turntables with a built-in preamp or other line level devices like CD players and Bluetooth speakers, use the aux input or other line level inputs.
By matching the correct audio input with your source device and ensuring proper amplification and equalization, you can enjoy the best sound quality from your audio system. Whether you are a vinyl enthusiast or a casual listener, knowing the main differences between phono and aux inputs will help you set up your audio gear with confidence and clarity.