3458A同步子采样模式存在偏差

当我通过频率为5 Hz至1.0 MHz的600欧姆馈通测量连接到3458A的600欧姆音频源输出时，DVM读数开始以130kHz和1.0MHz滚降，DVM显示器> -6％。
当我将Fluke 5700A宽带输出连接到DVM时，5 Hz到1.0 MHz的偏差为



     以下为原文

  When I measured a 600 ohm audio source output connected to the 3458A through a 600 ohm feed-through at frequencies 5 Hz to 1.0 MHz, the DVM reading started to rolloff at 130kHz and at 1.0MHz the DVM display was >-6%.  When I connected the Fluke 5700A wideband output to the DVM, the deviation over the 5 Hz to 1.0 MHz was <1.0%.  When I connected the terminated 600 ohm audio source to a HP 400F, the analog meter deviated <1% over the 5 Hz to 1.0 MHz.  What's happening with the 3458A? Is this a software issue?