Implementing a subcutaneous medical electrode system involves positioning a number of electrode subsystems in relation to a heart so that noise cancellation provides an improved signal to noise ratio of the cardiac signal and/or to provide one electrode arrangement preferential for cardiac signals and another arrangement preferential for noise signals. One of the electrode subsystems so positioned may include one or more can electrodes located on a housing enclosing a medical device. The medical device may be configured to provide therapeutic, diagnostic, or monitoring functions, including, for example, cardiac arrhythmia therapy.