Can the AMP1 be operated without a load (loudspeaker, reactive load, etc.) connected?
You do not necessarily have to connect a load to the AMP1, because it can also be operated without a connected load.
However, the amplifier sounds different if a real loudspeaker or a reactive load is connected to the SPEAKER OUT. So it makes perfect sense to take advantage of this effect in order to achieve the most authentic results possible.
Info: the impedance curve of a loudspeaker or a reactive load changes the frequency response of the output stage, depending on the negative feedback design of the output stage used. This effect is used to create more punch and bite, e.g. for heavy sounds. If no loudspeaker or only a resistor is connected, the frequency response remains unaffected, so it sounds rather "flat".
In addition, it is important to know that the volume of the AMP1 changes depending on whether a reactive load or a loudspeaker is connected: without a load connected, the AMP1 is slightly louder. In addition, the changed frequency response described above is also expressed in a measurable change in volume: if the sound has more present mids, it is automatically perceived as louder.
BluBOX
The current feedback design of the AMP1 also plays a role in combination with the BluGuitar BluBOX VSC. Depending on whether the THRU socket of a BluBOX connected to the AMP1 is occupied or not, both the sound of the amp and that of the BluBOX change. There is more on this topic in the article Volume change by assigning the THRU socket.