A few years ago there was a withdrawal of the entrance to headphones by several manufacturers of smartphones. This change began with Apple, but what many do not know is the difference in the use of digital connectors and analog input.

A few years ago there was a change (and is still occurring) of several models of cell phones, from several manufacturers, especially the top models, where they lost the entrance to headphones. This change began with LeTV and later popularization with Apple with the decision to remove the P2 entry of their iPhones and to use wireless headphones/ Bluetooth or Lightning 3.5 mm adapters. However, many do not know the differences that are had with the adoption of digital connectors and this is what we will discuss in this article.

What is Lightning?

How do USB, USB-C and Lightning headphones work? [basic on headphones]Lightning connector

The Lightning connector was introduced by Apple for use on its mobile devices (iPads, iPhones, and iPods) in the year 2012. It is a much more compact solution where 8 pins are used instead of 30 (old connector used by the manufacturer) and can be inserted from both sides (there is no right side).

Another advantage besides the size and the way of inserting the new connector is the fact of transferring data faster and charging the batteries faster.

What is USB-C?

How do USB, USB-C and Lightning headphones work? [basic on headphones]USB-C Connector

The USB-C (or USB Type-C) connector is a 24-pin USB connector that differs from other types by having symmetrical (equal) sides and being able to connect it in any position. In addition, this connector is capable of transferring data faster when compared to its predecessors and charges the battery of devices using this type of connector more quickly.

The first version of the USB-C connector was finalized in the year 2014, however, several updates of this connector have already occurred:

  • Rev 1.1 (03/04/2015)
  • Rev 1.2 (03/25/2016)
  • Rev 1.3 (4/14/2017)
  • Rev 1.4 (03/29/2019)
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What are the lightining headphones?

They are headphones that have cables with connector lightning and because of this, they have a different operation of a handset with cable P2 (3.5mm).

The output of headphones (P2) produces an analog electrical signal since the digital signal has already been converted and amplified by the integrated DAC/amp circuit on the smartphone’s board. As for the lightening connector, it does not use the DAC/internal cellphone amp as it produces a digital signal that is converted by the lightining cable (from the headphone or from the lightining adapter to P2) which has a DAC / amp circuit welded on the connector.

How do USB, USB-C and Lightning headphones work? [basic on headphones]DAC/internal amp on the lightning connector

Using the lightning connector for audio has the risk of limiting the audio quality offered by the handset since connecting a lightning cable to the phone will disable the internal DAC/ amp of the phone.

There is also the option to purchase adapters and lightning cables from other manufacturers, other than Apple, where a higher quality DAC/amp is used. This would be an alternative to getting higher sound quality without using a headphone jack.

What are USB-C headphones?

They are headphones that have cables with USB-C connector and because of this, they have different operation from a headset with P2 (3.5mm) cable.

The output of headphones (P2) produces an analog electrical signal since the digital signal has already been converted and amplified by the integrated DAC/amp circuit on the smartphone’s board. The USB-C connector does not use the internal DAC/amp of the phone, because it produces a digital signal that is converted by the USB-C cable (from the headset or the USB-C to P2 adapter) a DAC/amp circuit welded to the connector.

Using the USB-C connector for audio, therefore, you risk limiting the audio quality offered by your phone, because connecting a USB-C cable to the phone will disable the internal DAC/amp of the phone.

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However, today there is also the option to purchase USB-C adapters and cables from other manufacturers in which a higher quality DAC/amp is used (Examples: Hidizs Sonata HD DAC Cable II, iBasso DC01). This would be an alternative to getting higher sound quality without using a headphone jack.

Do USB PC headphones work in the same way?

Just like the cables with USB-C or lightning connectors have a DAC/amp internally, the USB headphones have also in their cables or in the internal structure of the headphone.

However, in the case of the PC, one can have the benefit of achieving a cleaner sound, without noise, due to better electrical insulation than the onboard sound card of the machine used.

Is there an alternative to not using USB-C / lightning adapters for P2 (3.5mm)?

Yes, there are alternatives. One of them is the use of Bluetooth transmitters such as:

  • EarStudio ES100
  • Fiji uBTR
  • FiiO BTR1K
  • FiiO BTR3

Another is the use of Digital Audio Players (DAPs) that connect to your smartphone via Bluetooth and you can control the music being played on your phone through them. Example:

  • Cayin N3
  • FiiO M5
  • FiiO M6
  • Hiby R3

Is there an alternative to charging the phone while using the USB-C / lightning adapter for P2 (3.5mm)?

Yes, if the adapter has a USB-C / lightning connector along with the P2 on the tip.

How do USB, USB-C and Lightning headphones work? [basic on headphones]Adapter to use charging and listen to music at the same time

USB-C Active Adapter Vs USB-C Passive Adapter

There are two ways the audio can be transmitted through the USB port:

Active: The digital signal is sent from the USB connector bypassing the built-in DAC/amp of the phone and is converted to the P2 adapter cable that has a DAC/amp internally.
Passive: The integrated DAC/amp on the smartphone card converts and amplifies the signal that is sent passively from the USB connector to the 3.5mm connector.

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However, not all smartphones are able to passively send the signal to the USB-C to P2 adapter cable. The protocol that allows a USB-C port to send an analog signal is the Audio Adapter Accessory Mode. The operation is done through four connections inside the USB-C connector that turn off any digital output and replaces four analog connections (left audio, right audio, microphone, and ground).

The smartphones that have the Audio Adapter Accessory Mode are the following models (the list can be updated over time):

  • Motorola Moto Z
  • Motorola Moto Z Droid
  • Motorola Moto Z Force
  • Motorola Moto Z Play
  • Motorola Moto Z2 Play
  • Motorola Moto Z2 Force

Conclusion

The decision to use USB cables or lightning was only a move by companies to earn more over the headphones as the technology will add value even more and will not deliver as many benefits. In addition, in the case of mobile devices, there is still the issue of not being able to listen to music if the device is being charged (unless the user has an in-ear or Bluetooth headset).

The only point that would have a benefit would be in the use on a notebook or desktop that does not have such a good onboard sound card and a circuit without good electrical insulation, so there is no interference in the reproduced audio.

If you need help, have doubts or concerns, do not hesitate to leave a comment in the comment box below and we will try to help you as soon as possible!



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