Icarus not entirely silent with no notes playing

[flexionmusic]

With some (home grown) patches Icarus outputs something at -70 DBFS when no note is played. Does anybody know what could cause this?

[Markus Krause]

Hello Flexion,

some filters do have self oscillation. This can result in output without notes playing. Some of the insert effects do output noise as lo-fi effect.
There is also a very small DC. It prevents the following plugins from denormals. As a result the CPU load is lowered drastically.