The relay is to work together with plug detections to realize which plugs are used, and which circuits should be enabled, balanced/single, and also disengage plugs as soon as possible to avoid shorting out between L+/L-, R+/R-, due to the nature of cylindrical plugs, when you pull it out, these terminal will temporarily be shorted out. To be able to disengage as soon as possible will prevent this which May lead to further damaging…mainly sensitive gears
There are 2 choices to have, using FET, or using mechanical relays. The ”One” series is a flagship with dedications and design come to mind, the body chassis is large enough to enable hosting the mechanical relay. Beside that mechanical relays will only have mechanical sound when turning on and off rather than a ripple within the electrical signal which cause “pops” on your IEMS or headphones when turned on.
Least and not last, the mechanical relays are designed for signals integrity and reliability in mind, the legs and conductors are made of pure silver, not jus the typical brass with gold plate. The ZX2 also had mechanical relays
Why no grounding on balanced ? Because the balanced output is full bridge class D, which is using ground as a Neutral reference while positive voltage is fed toward the “two” sides of the signals, which means it is amplifying a full 180 phase continuously with the usage of only 1 single rail of voltage supply. Therefore, if the Ground references has any slight differences, it will result in a differences in the amplifications and voltage supply behaviors. Most specifically is when plugging in, you will hear the noises which is due to the “Short circuit temporarily” between polarities. If you are also using a shielded cables with this ground connected, your cables will act as an antenna, which attract EMI/RFI, and then being drained, negated by the main circuit, which would cause ripples, different behaviors of the References plane (Ground) and related toward the amplifications circuitry. Then again, mostly observed is the ”Noises”. Keep in mind, Class D is very very very “Noisy” by nature, hence to design a high-end which is worthy of “High-res” certifications is not cheap, nor Easy.
Why is the Ground on SE working just fine ? Because it is a part of the amplification and not just a Neutral references anymore. It is now acting as a Neutral Negative return for all signals path, and because it is now a part of the amplification processing, every noises would be filtered out, while still “being effected by all the mentioned above”, the effects is negligible and not as significant as if it was on balanced. The SE is using a Half Bridge amplification implementation, which is totally independent of the Balanced out.
All of these, should be explained to you, the consumers, from the “vendors” who is selling “GroundEd adapters”, and or Cables vendors. They may be too busy caught with something else, and I have seen such questions unanswered for a while. I think this post will answer them, if not most of them
