s11e12 bass amp

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swingarm63

swingarm63

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Joined 2009
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I'd like to try building a bass amp with these tubes as I found locally for a very cheap price. The guy told me they are similar to 6550. They are not quite. The power dissipation is 28w. However I have an Ampeg V4 output transformer and an old Davis dual secondary plate transformer and a large filament transformer. I was reading in Gar Gillies tube amp how to estimate the mil rating of a power transformer. The transformer voltages are 438-0-438 and 330-0-330. His formula measuring from one leg to the center tap is to measure resistance then voltage divide voltage by resistance and multiply by 25. He says its accurate up to 200 mil. However I get a much larger mil value. 438/22ohms=19.90 x 25 = 498 mil so maybe this is to large to be accurate. The amp did run 4 6l6 but I'm not sure about the circuit it ran. anyway, the second secondary is 330/147 ohms=2.25 x 25= 56 mil. Unloaded voltage to the plates appears to be around 620 volts. I'm going to use solen plastic fast caps in the power supply. what do you guys think I need min or screen filtering?

what I thought I might do is try to drive the s11e12's screens and the PI and pre from the 330-0-330 winding and the plates from the 438-0-438 winding. seems like I might have to reduce the screen voltage maybe with a mosfet and zener?I also thought I might try a moset Source Follower Drive for Output Tubes. like here http://www.geofex.com/Article_Folders/mosfet_folly/mosfetfolly.htm The max screen voltage in the manual is 300v. I was going to run this with 4 s11e12's and a svt preamp. what do you guys think?
 
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