Cap Multiplier test

I managed to find the time this weekend and do a quick test on the Cap Multiplier PCB. It turned out that I missed a thermal pad on the PCB so had to add a short jumper. Nothing major, but the PCB needs adjustment.

Below is the diagram of one of the ways the PCB can be used. This is the most complex circuit, a basic one can be wired instead. The CCS (M1 and M3) provides better PSRR as well as regulation. A stable current is fed to R4 and P1 to set the voltage. C2 is the cap multiplier and the M5 used can be any suitable MOSFET. T4 provides current surge protection to the MOSFET as well as short circuit. R7 sets the current limit.

The boards fits various film caps, I have some WIMA DC Link which are great and fit perfectly:


Continue reading “Cap Multiplier test”

UV-201a DHT Preamp Revisited


I previously implemented a preamp with the UV-201a. These are very old globe valves, somehow fragile and hard to get in good shape. Despite all this, it’s a superb valve. I have managed to acquire a decent set of them to pair the best valves to use in my preamp.

Recently I developed a prototype PCB for the source follower circuit. The source follower is ideal to place at the output of this preamp due to its low driving current. My 4P1L PSE amplifier will be pleased with more current to pump the Miller capacitance effectively. 

Continue reading “UV-201a DHT Preamp Revisited”

SiC MOSFET Follower Driver

How many more times

Led Zeppelin wrote a fantastic song on their first album: how many more times. You may not be a rock fan, but hey: what a great song. How many more times do I want to get back to this “slew rate” theme? I don’t know, as much as I have to. Plenty of comments out there of bad designs with wimpy drivers attempting to take the 300B/2A3 or even 45 valves to full tilt with disappointing results. Either way, they always blame the valves.

I came back to revisit the driving of capacitive loads effectively as I’m working on a new 4P1L PSE amplifier. Slowly, but getting there. Previously I looked at adding a buffer to the 01a preamp as a result of slew rate limitations found in Tony’s implementation of this preamp.

buffer

 

 

The circuit design

Continue reading “SiC MOSFET Follower Driver”