Tuesday, March 1, 2011

The "Fletchinator" power supply

Here's a first sketch for the power supply for the amp I'm doing for my "Brother-From-Another-Mother" Chris Fletcher, proprietor of The Canadian in Uznach, Switzerland, and a damn fine guitar player.

This amp is going to be by far the most ambitious I've done to date.  If it works as planned, it's gonna be insane. A power scaling 100W head with Dumble-inspired topology, but with built in reverb and a high quality effects loop.  If it doesn't work as planned, well then, it'll be a noble experiment and expensive bust.

The intention here is to do a power supply that is totally modern. You won't find this in Grandpa's Fender. It implements variable voltage regulation (AKA power scaling) for the power tubes and phase inverter, uses a capacitor multiplier instead of a choke for filtering the power tube screens, and amplified Zener regulation of the preamp tubes.  This is obviously inspired by Merlin's latest book.

As I said, this is just a sketch. I'll need to replace the MOSFET shown on the VVR with something substantially beefier.  I'll probably also want to reduce some of the voltages across the board, and also tweak some of the values when I get better estimates of the power tube plate and screen currents. The preamp currents should be pretty accurate though.  Some of the PSU caps will be pretty close to their maximum rating, so I'll have to give some thought to that as well. I'll have to take a look at how well it'll do with start up transients.  Let me know if you have any other comments.

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