Was talking with various audio people about the 6C33C I was amazed that people are so clueless about this tube. The people are so filled with some foolish prejudges and faulty notions about 6C33C.
The 6C33C has only one equivalent: 6C18C. The 6C18C is an early version of 6C33C, might be used as drop-in replacement. The 6C18C is very good tube, in some instances is better sounding then 6C33C but in may experience the 6C18C has a large percentage of faulty tubes.
Properly used 6C33C is truly a problem-free tube with opportunity to have excellent sound if it is appropriately used in amplifier. So, I was disappointed with moronic myths that audio people invent about this tube and to address that stupid audio-prejudicial folklore....
The Lamm Industries,Navison Audio,Supratek,Ayon Audio,Balanced Audio Technology VK-60 and many more high end brands use this tube extremely well.
The design used is a variation from Futtereman and directly following on the Transformer is a small Value Paper in Oil Capacitor to sink noise. The rectifiers are superfast, soft-switching uniits from Motorola which are followed by another Paper in Oil Capacitor to sink rectifier noise.
A pair of Allen Bradley Resistors are insered in front of the first reservoir capacitor. All this quite sucessfully simulates the behaviour of a Valve-Rectifier with it absence of switching noise and Current-limiting behaviour. The first reservoir capacitor is also fairly small in value, again very similar in application to Valve rectified Supplies.
A very usual LC filter cell using a Maplin sourced Choke reduces the Ripple significantly. This then is followed by an "amplified capacitor" Circuit which removes any remaining ripple and provides a vrey low source Resistance.
In the end we have a balanced sound with extremely good details and impact.