external power supply question, will it work??

hey forum, quick question regarding external power supply units for a preamp.  the original amp manufacturer does have an optional supply to replace the dinky wall wart (rather pricey), but there are also many available external power supplies from other manufacturers.  my question is, can i use any external supply that has the correct voltage (appears to be 24v in the case of this unit), and expect it to work, or are there other specifications that must be met for compatibility, and if so, what should i look for?

thanks for any assistance / info the forum can provide.