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In the Forum: Melquiades Amplifier
In the Thread: Do the Filament Transformers Require a Center Tap?
Post Subject: Freed No. 28130 is probably sufficient for mePosted by Iraschwips on: 10/9/2017
Anthony and Romy, thanks for taking the time to respond to my question. I want to take on this project as a learning experience both in terms of simply building an amplifier from a schematic and for my edification on sound reproduction.
I’m starting out by doing some planning and picking out the chassis mount parts. Based on what you’ve said I think I found a filament transformer which will work. I also from the same supplier picked up some Johnson 7-pin (1 large) sockets, which I’m sure I overpaid for.
I’m going to attempt to build just the full range schematic, as mono blocks, not any kind of multichannel version. The filament transformer I ordered (x2) is a Freed potted transformer model No. 28130. I wasn’t able to attach an image but you can search for the image online. It has two secondary windings, a 6.3v and 12.6V. The former rated at 1.8A, the latter rated for 5.5A. The 12.6V is center tapped. I think for my application the current handling should be sufficient. Looks like the tube data sheet for the 6C33C shows that it requires 12.6V when heaters A and B are wired in series. A parallel heater connection halves that number. I guess I will heat both tubes from separate windings; the 6E5P from the 6.3V winding and the 6C33C in series from the 12.6V winding.
The next big decision to make will probably be which output transformer to buy, whether I should go with the Lundahl LL1627AM or something else with a 300-350mA gap so I can drive the tube harder. My speakers right now are four-way dynamic driver units rated very optimistically at 97db. It’s probably more like 92-94db.
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