Spider Valve 112 Direct Out & Standby Switch Operation

[kjralyea]

I have recently acquired a Spider Valve 112, and have a question regarding the use of the Balanced Direct Out. Normally, when operating the amplifier in the simplest fashion (nothing connected to the Direct Out on the back), the Standby switch operates as expected. In the DOWN position, there is no output to the speakers...in the UP position, the speakers are active. HOWEVER, at a recent performance, I connected a microphone cable from the Balanced Direct Out to the stage sub-mixer to send to the FOH PA. Surprisingly, I found that the amplifier speaker is now ALWAYS active...turning the Standby switch to the DOWN position still sends amplified signal to the speaker. Disconnecting the mic cable returns the amplifier to the expected operation. Has anyone else noticed this? I don't think there was any phantom power coming from the mixer, but, even if there was, I don't understand why that would have any impact on the operation of the Standby switch by the Balanced Direct output. I'm anxious to see if anyone else can confirm if their amplifier reacts in a similar fashion. 

Thanks.