Two things to consider when choosing and using multi layer ceramic capacitors (MLCC): 1. If using them for decoupling directly across the output of regulator devices whether linear or switching, check the regulator device datasheet carefully for advice on the use of MLCC capacitors. 2. In all applications, be aware that all ceramic capacitors except for those using C0G or NP0 (or similar) dielectric materials have a significant, non-linear dependence of capacitance on DC voltage across the device. The mechanism is complex and poorly documented but essentially, the capacitance falls with applied voltage. The non-linear relationship means that if an MLCC with a quoted capacitance of C and a rated voltage of V used with an applied voltage of about V/3 will have an actual functional capacitance of about C/2. If the applied voltage is increased to V the capacitance will reduce to somewhere around C/10. This phenomenon is poorly documented because, surprisingly, it does not form any part of the official definition of dielectric types. It is also so poorly documented that it is not clear how the capacitance change keeps up with the rate of change of the voltage across the capacitor. It does appear that the capacitance will change with applied voltage at least into the audio frequency range which means that it will produce significant signal distortion. This phenomenon is sometimes referred to as Voltage Dependence of Capacitance (VDC) or Voltage Coefficient of Capacitance (VCC). Unfortunately VDC is often not documented even by some of the leading manufacturers and has actually got worse with recent developments in MLCC manufacturing technology. So, when choosing MLCCs try to find parts that do have graphs showing VDC. If VDC information is not available then try to find parts using X8R or X7R dielectric and select the highest voltage rated part in your chosen package size. If a suitable part with an X7R dielectric is not available then in descending order of preference, look for X6R, X5R then X7S. Avoid using Z5U or Y5V dielectric capacitors: they have nothing to recommend them. Another aspect of these types of dielectrics (referred to as Ferroelectric) is that they are also microphonic. This means that they mechanically deform with applied voltage and so generate sound when AC voltages in the audio range are applied across them. Conversely, they will generate a voltage across themselves in response to an externally applied mechanical deformation. In other words they behave like little microphones. This in combination with the inherent charge conservation of a capacitor, leads to an interesting effect where if a capacitor is charged to some dc voltage and so the capacitance has dropped to some fraction of it's rated value due to VDC, then if the capacitor is mechanically deformed (i.e. is subjected to vibration such as sound waves) and the voltage across the device rises then the capacitance will fall further. Due to charge conservation, this will cause the voltage across the capacitor to increase further which will in turn drive the capacitance down causing he voltage to further increase. There have even been cases in capacitor banks where this has caused a catastrophic increase in voltage sufficient to cause flashover between closely spaced capacitor terminations. For more about VDC, see: [https://www.edn.com/design/analog/4402049/Temperature-and-voltage-variation-of-ceramic-capacitors--or-why-your-4-7--F-capacitor-becomes-a-0-33--F-capacitor](https://www.edn.com/design/analog/4402049/Temperature-and-voltage-variation-of-ceramic-capacitors--or-why-your-4-7--F-capacitor-becomes-a-0-33--F-capacitor) or: [https://www.edn.com/Pdf/ViewPdf?contentItemId=4402049](https://www.edn.com/Pdf/ViewPdf?contentItemId=4402049)

Agreed.  The ones I found are X7R so I assumed the horrible Y and Z ones were long gone.   And yes, drop the 7805s and use a modern regulator. But remember electrolytics also change value both with voltage AND time. I was also saying used them for decoupling supplies, not signal transfer.  Electrolytics, polyester or preferably polypropelene are the only choices for audio.   Even X7R will distort the audio and NP0s aren't perfect either.