mwhouston wrote:
What do you think of using MKP X2 caps for the two inter-stage caps?
Actually I view this the same way that I view using motor run caps in a power supply filter. (
See those comments here.) If they work out (and it sounds like they have) then that's great. But I don't typically use components in "off design" applications if I can avoid it. Let me explain.
MPK X2 caps are thin film capacitors designed for EMI suppression while connected directly to the mains. As such, they are designed for several safety related characteristics. Generally in compliance with the standards IEC 60384-14 or UL 1283 / UL1414. The Vishay application note on the subject lists the main requirements of these types of capacitors as the following:
• Excellent capacitive filter: Low inductance and equivalent series resistance are preferred
• Withstanding pulse loads: Uncontrolled mains switching must be sustained
• Continuous biased by the mains voltage: A powerful energy supply is always available
• Withstanding surge voltages: High energy surge voltages could destroy the capacitors
• Safe end of life behavior
One thing you will not generally find on the list is low noise or high fidelity audio performance. Now, by their very nature, well made thin film capacitors tend to have good audio performance. However, other design features may compromise that performance while meeting the primary requirements for the part. And the builder really has no way to determine what design trades were made in order to meet the primary requirements.
As always, I'm not saying that they can not be used or that they won't sometimes give good performance as coupling capacitors, it's just that they are not designed for this type of use. As such, it's a case of let the builder beware.
Just my opinion.
