[sdiy] VCO reference voltages

[David G. Dixon]

Does anyone here have any strong views on deriving reference voltages from
the power supply rails in VCOs for comparator or schmitt trigger thresholds,
etc (as opposed to using precision references)?  I know that most "DIY" VCO
designs do so.  I'm wondering whether most commercial VCOs also do so, and
whether it is considered "kosher", even in more expensive VCOs.