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okay i have a few questions i cant seem to figure out.
i scored some vintage hammond transformers and enclosures from a retired tube radio guy. I love my Model T but i wish it came in a smaller package or maybe a preamp. OR BOTH!!
I scored a vintage hammond 261C6 transformers. 250V C.T @ 45ma and 6.3v @1A
I also have a pulled SE 6K6 OT from a 50's tv unit.
My Idea is to build something like a Garnet Herzog but with the capability of being a small 5W amp or a preamp. I plan to use a single input but have both the normal and brite channels still blendable like in the original T.
that part is easy but what im trying to determine is if the PT can handle all that power.
12ax7 heater current = 0.3A x2 = 0.6A
6K6gt heater current = 0.4A x1 = 0.4A
for a total of 1A. heaters should be ok.
calculated out i have the 2x12ax7 and 1x6K6 drawing 55ma of current... is going over the 45ma rated transformer by 10ma going to cause a meltdown? this is a 40yr+ old unit and i would think it could handle the juice.
My last question is how would one add a presence control if there is no P.I? since this would be a SE design a long-tailed phase-inverter is out.
I came across this explanation but since my driving stage for a SE output would be v2b. would it affect the overall tone?
"You just need to add a global feedback loop from the transformer's secondary and inject that into the cathode of your driver stage through a voltage divider and then shunt the highs to ground through a .1uF cap and a variable resistor.
Assuming that there is a common cathode driver stage, like half a 12ax7, just add a resistor to ground beneath the current cathode resistor and apply the feedback to the junction of the two through a series resistor. That will form a voltage divider to let you control the amount of feedback.
That junction is also where you put the presence control. Wire one side of a .1u cap the the junction and the other to the wiper of a pot and ground one of the pot's other terminals."
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