I've had both devices and had constant problems with the 56, but I can recommend the 57 100%. It's great and the aerial fits both.

Inside the device it has a metal plate that is held magnetically with the supplied holder. I used a different magnetic holder to attach the device to the centre console.

The device needs a usb power supply (5 volts) you can also make a connection from the car battery

Yes, the antenna is included with the Albrecht Dr 57. The antenna supplied is specially developed for the device and offers optimum reception quality.

The FM transmitter of the Albrecht DR 57 transmits the signal in stereo. The description of the product does not mention any restriction to mono sound, and it is emphasised that the device offers high-quality signal transmission, including the use of an intelligent FM transmitter that minimises interference and ensures clear transmission.

You can theoretically use a different DAB+ antenna, but there are some restrictions to consider. The active DAB+ foil antenna supplied with the Albrecht DR 57 has been specially developed for the device and offers optimum reception quality thanks to magnetic earthing. - It is not guaranteed that another antenna will provide the same reception quality and stability, especially if it does not have the same technical specifications as the supplied antenna. - Compatibility also depends on the type of connection. The supplied antenna is specially designed for the device, so the alternative antenna should have the same connection in order to work properly.

Only the sound is transmitted. There are no Spotify functions on the device itself. You have to use them on your mobile phone.

So far, I have not come across such an "Auto Standby" function. I operate the device on my 12V connection on the console (vulgo cigarette lighter socket) inside the vehicle (Mercedes-Benz B180, JG 2011), which is conveniently switched off at the same time as the ignition is switched off. This way, the problem of battery discharge does not arise in the first place. Otherwise, take the 12V power supply for the Albrecht DR57 from the switched power supply of the ignition lock.

Yes you can, because it doesn't matter which antenna as long as the connection fits.

Since the connections on the unit and on the antenna (probably this one: https://www.digitec.ch/de/s1/product/hama-dachantenne-amfm-und-dabdab-din-smb-kfz-antenne-3456812) are the same (SMB), this should work without an adapter.

More than long enough, Initially fed it hidden down the Windscreen post, across half the windscreen down to the console beneath the vents and still had enough. Since the suction fixing is best on glass, I now have it on top of the dashboard, all cables hidden and the arial is small enough not to disturb any view at all. Works really well, either using local FM or an AUX cable.

First of all, only 99 stations could be read in with the old DR 56. This is also too few for us, because transmitters that are present in different bouquets are also counted and displayed several times. The DR 57 can read in 230 stations. (However, there is now an updated version of the DR 56 that can also read in 230. According to Albrecht customer service, however, this cannot be distinguished from the old one, so you may or may not be lucky). The DR 57 has the "Service Follow" function, which was not yet available on the 56. If a station is available in different regional bouquets, which is also the case with us, the unit automatically switches to the same station in the other bouquet. It also automatically searches for the strongest signal if a station is present in several bouquets. Since this can also be annoying, you can deactivate the function, because there is a short interruption each time you switch. The 57 also has 5 favourite buttons, the controls are different and the size and shape are different. If you were technically interested, you could see which channel or frequency you were on with the DR 56 and then knew from which bouquet a station was currently being received. This is no longer visible on the DR 57. You can only see the bouquet designation behind the station name in the station list, e.g. N-CH for the Northern Switzerland bouquet or O-CH for the Eastern Switzerland bouquet.