The reasons are summarized only where necessary. There are many cables on the market that allow prohibited connections. We hope you will take a look through it to prevent accidents.

◆Continuously connecting cables with unbalanced connections to an amplifier with a balanced design may cause malfunctions.

*If the amplifier is designed with ground isolation, it will not cause failure. (However, it will not receive the benefits that the designer may have intended.)

What is balanced design?
What is ground separation?
Why would a faulty connection cause damage to the amplifier?
These issues will be briefly discussed.
 In general, examples of unbalanced, ground-separated, and balanced connections are shown in the figure below.
 The pin assignment of the 4-pole plug in the figure is just an example.

１．
3-pole GLD(L-R-) common] Unbalanced connection
(This is the most standard method.)　　　

The cold side of the L and R channels are wired to a common GND on the amplifier (player) side.　
Use a 3-pole plug as shown in Figure 1 for connection to the amplifier. (The electrodes are divided into three sections.)

[Key Features]
・GND current is mixed in LR and crosstalk increases, resulting in a muddy sound.
・Less distortion compared to a balanced connection. (Compared to balanced drive using the same amplifier)


２．
4-pole ground isolation connection] Pseudo-balanced connection
(e.g. SONY NW-ZX2, NW-WM1Z/1A (Φ3.5mm jack), OPPO HA-2, HA-2SE, etc.)

The cold side of the L and R channels are wired to LR independent GNDs on the amplifier (player) side.
 Use a 4-pole or larger plug as shown in Figures 2 and 3 for connection to the amplifier.
 
[Key Features]
・Independent GND at LR prevents GND current from mixing at LR and reduces crosstalk. Separation is improved.
 ・Less distortion compared to a balanced connection. (Compared to balanced drive using the same amplifier)


３．
4-pole balanced connection*Here's what you need to pay attention to connect, CAUTION!
 Example: SONY NW-WM1Z/1A (Φ4.4mm jack), AK (Φ2.5mm jack), etc.

The L and R channels hot & cold are all connected to independent amplifiers.
 Use a 4-pole or larger plug as shown in Figures 2 and 3 for connection to the amplifier.
 
[Key Features]
 ・The + side and - side are driven by independent amplifiers, so that four times more power can be gained.
 ・The two amplifiers, one in the positive phase and the other in the reverse phase in LR, are connected separately, so the signals (in LR) do not mix and crosstalk is reduced and separation is good.
 ・Since the GND is floating, it is not easily affected by GND, which tends to be unstable in a portable environment.

Going back to the question, why can't a 3-pole plug be plugged into an amplifier that supports balanced connections?
 The difference between a 4-pole plug and a 3-pole plug is that the L- and R- are shorted or not.


In the case of ground separation in Figure 2, even if L- and R- are shorted, the LR GND current will be mixed and crosstalk will only increase, resulting in the same connection situation as an unbalanced connection.
However, if L- and R- are shorted in a balanced connection, the load will continue to be applied to the limit of the amplifier. This can result in damage to the amplifier circuitry. Special care should be taken because even if this condition occurs, the user may continue to use the amplifier without noticing it at first hearing.

It's rare, though, that a 3-pole plug inserted by mistake into a 4-pole jack will break instantly.
Continued high load conditions such as those described above will place a heavy burden on the amplifier circuit.
We hope you will enjoy our balanced conversion cables with the correct wiring method, taking the above information into consideration.
　
In addition, we rarely see users with balanced cables plugged into headphones that are not compatible with balanced cables.
In this case, too, a short-circuit condition is created as described above, and a high load is placed on the amplifier circuit.
For example, the MDR-1R from SONY does not support balanced connection, but the MDR-1A does.
Balanced and ground-separated connections are very advantageous in terms of sound quality, but if the correct connection method is not used, expensive equipment may be damaged.
We hope you will enjoy your portable audio life with the correct wiring method.

If you have any other questions, please feel free to contact us.
If you let us know which amplifier and headphones (earphones) you are using, we can consult with you on the production of a balanced connection (ground separated connection) cable.