Cool. Someone to pave the road...somewhat. Ive decided when work slows a little, I will make a huge SE transformer. I've been studying the Radiotron Designer's Handbook on tranformers, and a few other sources. I've followed 3 different design methods and came out with roughly the same facts. The RDH has a lot of info on what limits the results, and I think I can do reasonably well.
Here's some herasy for you all... I plan to drive a 833 with a lm3886 up near it's voltage limit. Should be able to give plenty of grid current on the positive swing. This ofcourse isn't the final solution, but just to test the transformer. (although it would really tweek the tube world) After I get the iron pumpin, I'll work on a front end.
Who knows, I may put a few of my employees to work winding transformers and start a little side business if it works well.
Here's some herasy for you all... I plan to drive a 833 with a lm3886 up near it's voltage limit. Should be able to give plenty of grid current on the positive swing. This ofcourse isn't the final solution, but just to test the transformer. (although it would really tweek the tube world) After I get the iron pumpin, I'll work on a front end.
Who knows, I may put a few of my employees to work winding transformers and start a little side business if it works well.
Hey I tend to sprinkle some sand into many of the tube amp designs that I build. In this case PowerDrive is made up from a CCS chip loading the driver triode, followed by a mosfet source follower to drive the grid of the output tube. The email was predominately negative at first, but a few brave builders actually tried PowerDrive, and liked it. One of those builders stated his praise for PowerDrive, on this forum. Now I get requests for more information.
There are many "sandophobic" people that will not use silicon ever. They don't know what they are missing. Careful, well designed solid state circuits can be a benefit to tube amplifiers.
There are many "sandophobic" people that will not use silicon ever. They don't know what they are missing. Careful, well designed solid state circuits can be a benefit to tube amplifiers.
I was thinking of taking an octal base and making a plug in module including a nice looking heat sink with a big fet nicely attached. Like a sand tube. Maybe even a bizarre hand made heat sink like a small bar of copper with many rows of holes. into each, insert a 12 ga solid copper wire and solder teh whole mess with plumbers torch, flux, and sn/au solder. Then bend all the wires in a nice design to somewhat mimmic a sholdered bottle design. Like spaggetti.
It seems the solution to leakage inductance is a lot of interleaving. Capacitance (I don't thnk) is the major source of high frequency roll off. With things like Plumbers teflon tape, I can keep the capcitance down.
The secret will be many paralleled windings of small wire with 10 or so interleavings. This will cut leakage inductance by a factor of 100.
It seems the solution to leakage inductance is a lot of interleaving. Capacitance (I don't thnk) is the major source of high frequency roll off. With things like Plumbers teflon tape, I can keep the capcitance down.
The secret will be many paralleled windings of small wire with 10 or so interleavings. This will cut leakage inductance by a factor of 100.
Aha! This was the thread I was looking for:
Beyond SET and ParaFeed.... Complementary Current Triode.
Beyond SET and ParaFeed.... Complementary Current Triode.
OK, so there's no free lunch, so I need a biggassed SE transformer. I've played around with a few ideas and checked leakage inductance and capacitance charts in the Radiotron designers Handbook, and I think leakage inductance isn't the problem. It's the capacitance with high impeadance (8k) primarys. many layers of interleaving is out. I need space and vertical sectioning. Big iron with less turns also looks like a plus.
Thanks to smoking amp for the scale analysis. I found a stamping I like, 3" of which will weigh 40 lbs. I'll likely make 5 or 6 coils before I'm happy though. What would be an easy hookup to test the results? The standing bias shouldn't effect measureing the leakage capacitance. I could just hook LC meter to one B+ lead on primary, and 16ohm tap of secondary. To test primary inductance, I could put a current source on the secondary(with a choke in series), and feed current to get amp turns same as will be on the primary and test with LC meter. shorting the secondary I can test the leakage inductance at 0 bias. If I add a voltage source, I coud test with bias.
My goal is to optimize the transformer before I start on the amp.
Thanks to smoking amp for the scale analysis. I found a stamping I like, 3" of which will weigh 40 lbs. I'll likely make 5 or 6 coils before I'm happy though. What would be an easy hookup to test the results? The standing bias shouldn't effect measureing the leakage capacitance. I could just hook LC meter to one B+ lead on primary, and 16ohm tap of secondary. To test primary inductance, I could put a current source on the secondary(with a choke in series), and feed current to get amp turns same as will be on the primary and test with LC meter. shorting the secondary I can test the leakage inductance at 0 bias. If I add a voltage source, I coud test with bias.
My goal is to optimize the transformer before I start on the amp.
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