Hi 4 everyone. Why u dont try to make it by your selfe. See attach for example. I think that will do a job. In worst case u can damige a diode. But thay are cheap ;). Sound card is practicaly isolated from source because input resistance of op.amp. is, theoreticaly, infinite. Only defect is low speed of response and, of course, low frequency band. I think that is 44khz for n-vidia sound cards, but I, also, think that will not work over, lets say, 30khz. I am going to project a very good interface for it with big frequency bandwidth and lots more... :) I will send it here when/if I do that. atenuator_4_digital_osciloscope.zip