New version of the Universal PreAmp arrived. I've had these on Ebay for years under HVFORLESS. I took down my listing during COVID for personal reasons. Then I noticed a project that kicked up in my absense. A few folks here reversed my board and added a few features. I would have loved to be in on that, but I noticed the thread too late. There were good ideas there. I took a few of those and added some of my own. 100 boards are already in hand, so any good feedback won't show up until the next revision.
- Octal socket on the board for optional tube rectification!! Options on board are now full wave, center tap, or tube.
- HV and LV ground planes.
- Grounded heatsinks for safety and heat dispersion (must use an insulator pad).
- Vent holes where needed.
- Gate resistor in Miada circuit (allows for MOSFET if preferred).
- Additional pads and larger diameters for electrolytic caps to accommodate multiple options.
- Trimmer resistors and jumper moved to more accessable locations.
- Fully scrubbed BOM with alternates listed for most components. Cost reduced with highly available parts.
- Optimized layout. Routing on top side with few exceptions, and no VIAs.
- Same 4" X 6.25" footprint and 2 ounce copper.
- Trace widths optimized for worst case currents with at least 50% safety factor.
- Spacing and isolation optimized for worst case voltage differentials.
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It's a universal power supply for literally any preamp design. I developed the first version years ago for some personal projects, and then had extras made that are available on Ebay. The heater section of the design is rather unique. It allows for a standard 6.3VAC input and is rectified to 6.3VDC or 12.6VDC. Just must move a jumper and dial in a trimpot to switch between the two. No need to pull out the soldering iron to switch between a 6SN7 and a 12SN7. High voltage is also regulated and dialed in with a trimpot. Additional features are there for whatever type of high voltage rectification is desired and choke vs CRC resistor.