Dear Steve,

I am copying a paragraph from the datasheet of 4051:

" Vdd and Vss are the suppy voltage connections for the digital control inputs (A0 to A2, and /E). The Vdd to Vss range is 3 to 15V. the analogue inputs/outputs (Y0 to Y7, and Z) can swing between Vdd as a positive limit and Vee as a negative limit. Vdd-Vee may not exceed 15V.
For operation as a digital mux/demux, Vee is connected to Vss (typically ground). "

A0, A1 and A2 are 3bit inputs.
Y0 to Y7 are 8 channels.
Z is the common I/O for Ys.

Actually I have to make a digitally controlled volume control of a small audio amplifier.

I have connected 8 different value resistors between channels Ys and ground and have connected the common Z to the input of the amplifier.

Normally it works fine. but for a volume control which is dynamic (voltage controlled volume) it damages the micro as somehow the volume controlling voltage (12V) gets into micro.

How about isolating the inputs A0 to A2 from the micro ports ??

Babar/