You need to be careful with these 24 to 12 volt converters.
Ideally to suit the Amel system you need an isolated converter i.e. one where the input negative is isolated from the output negative.
If you use a non-isolated converter where the input negative is connected to the output negative, then you will have a direct path from the house battery negative to the ships ground when you connect to the Icom SSB, as inside the ICOM SSB the -ve 12v rail is connected to ground. This is anathema to the Amel grounding system of isolating the battery negative from ground.
So, to avoid this you either need an isolated 24-12 converter or, do what I did, with a non-isolated converter, and put in a relay to completely disconnect the converter from the SSB when its not in use.
The Victron 24-12 unit mentioned is not an isolated unit.