High radiocarbon sample throughput is an increasingly important requirement of accelerator mass spectrometry (AMS) systems, which in turn requires high source output. To accomplish this, HVE AMS systems use a model SO-110B ion source, which can run at outputs of more than 200 μA 12C. It is known that high source output may compromise precision. To quantify this effect, we have tested an HVE 1MV AMS system for the influence of medium (100 μA) and high (200 μA) source outputs on the precision. These early measurements indicate for a 200 μA 12C source output, equivalent to a ≃1 kHz 14C count rate for Ox II samples, a 13C/12C precision of 1% and a 14C/12C precision of 3% can be obtained.