Transformer-less Output- Not What You Think

[silverfox]

I've heard of audio transformer-less outputs mentioned in the Ausie Dude's site, but, Transformer-less output as applied to say, 450 MHz. Has that been done in the past? And perhaps but also adding an inductor to load the transmission line. The plates configured as center taped  PP for RF?


silverfox.

[shooter]

somewhere I've got a couple examples for tube amps but can't find them 
In the RF or audio transistor world they're almost all OT-less. 

[silverfox]

I don't know what I was thinking last night. I'd forgotten even CB class RF has no OT.


Here's a link to OTL audio. Lots of other great stuff here. http://www.turneraudio.com.au/OTL-amps-pros-cons.html


Thanks Shooter.


silverfox.

[PRR]

You "can" use a transformer at 450mc, but often a Pi network is simpler.

[DummyLoad]

https://www.transcendentsound.com/evermore-otl-amp.html

https://www.transcendentsound.com/mini-beast.html    << for the SE freaks. 

https://www.transcendentsound.com/bruiser.html  << for power mongers.



bruce rosenblitt's company - he published a beginners guide to tube amp theory i read a long, long time ago.


--pete

[silverfox]

Originally started this as an RF related thread. However, I've now got some audio related questions concerning OTL amps. What range of voltages are present on the output driving the speakers? Hard to believe 40 volts and a capacitor in the path of the anode will cause any significant current in the speakers. According to the information at the site linked in my post, OTL does not compare favorably with the classic OT designs.

edit: Seems to be 40 to 100 volts on the outputs.

I still can't believe I forgot, nearly the entire RF spectrum is driven by tubes or semiconductors. Must be getting old. But then, spouse is away and I've got lots on my mind.


silverfox.

[shooter]

40 to 100 volts on the outputs.

at the speaker it's no longer about V's, it's about I's.  40vac @20A makes lots o power 

[silverfox]

40 to 100 volts on the outputs.

at the speaker it's no longer about V's, it's about I's.  40vac @20A makes lots o power 

turneraudio site is like, "the Brain Explains OTL". Lots of graphs you can pick data from, but even then he suggesting- Add a transformer to match the load. Well, that aint transformer-less,  Very knowledgeable, but almost a complete course in any question you pick.
What I don't understand is how the translation of 160 plus volts to 40 vac- With a coupling capacitor; Okay. The internal resistance of the tube is what 84K ohms?. The tubes are running at a high voltage. How is the power in the tube coupled to the speaker without putting high voltage on the speakers?


This is starting to sound like an MRI machine or something. I wonder what they drove the field with in those?


silverfox.

[shooter]

drove the field with in those

we used 3 split rail PS's, +/-160vdc, fused at 100A
pick a 1mm "point" in a 40cm sphere, do spooky math and pulse XYZ, (gradient supplys) into a copper foil coil, do more spooky math, transmit a 25kW pulse and walla, all the atoms are now spinin sideways 

[silverfox]

drove the field with in those

we used 3 split rail PS's, +/-160vdc, fused at 100A
pick a 1mm "point" in a 40cm sphere, do spooky math and pulse XYZ, (gradient supplys) into a copper foil coil, do more spooky math, transmit a 25kW pulse and walla, all the atoms are now spinin sideways 

Now that's the kinda dope I'm lookin for. But the 25kW pulse must have come within what, 250 ns of the 3 phase pulse? Set em up and read em. Sounds like Star Trek.


Why copper foil rather than wire for the field winding's? Were they using the capacitance of the foil to launch the field, or something to do with avoiding an inductive reactance issue?


silverfox.

[shooter]

Why copper foil

there are basically 2 electromagnetic circuits, the one that creates the main field is "star trek" wire, submerged in liquid He.  the PS for that is designed for "that" magnet.  you plug in 2 probes, cable it with 1.5" multi-strand "welders" cable.  The PS is auto-sensing n controlled, mostly.  Takes about 1-3hrs to sneek ~320A into the niobium, once you're at the target field, flip the switch, remove the PS and, near perfect electromagnet.
the others are the XYZ gradient coils, they are wound into a fiberglass tubes, stuck inside the main field used to "move the field".

the 25kW

that comes from a tube rated at 500W(?) CW, hit it with a 1mS 10% duty cycle. lasts ~ 18Khrs or about 10 months on a busy system

it was fun kinda sorta understanding the deep theory, but there were sooooo many parameters, calibrations, complex faults, upgrades that I just sorta glazed over the "whys" and focused on my job, uptime and meeting OEM specs

 

[shooter]

silverfox, here's the un-intended consequences list 

wandered off to wavelength found a cool calculator
a comment from Sluckey about filaments using fullwave, and your questions of MRI lead me to wonder if  Gaussian pulse was "full wave", lead me to places that required a refresher puff 

[silverfox]

silverfox, here's the un-intended consequences list 

wandered off to wavelength found a cool calculator
a comment from Sluckey about filaments using fullwave, and your questions of MRI lead me to wonder if  Gaussian pulse was "full wave", lead me to places that required a refresher puff 

Now you got me going. https://www.youtube.com/watch?v=Ok9ILIYzmaY


Protons polarized are hit with RF. When the protons resonate back to the rest state in the magnetizing field, they emit RF that is detected to create a thermal type image. I think the human body operates on similar concepts, the 6th sense.

[shooter]

the 6th sense.

when you work inside a hi magnetic field you can "sense" as you move across the field (cutting lines of flux), move to quick and you'll drop to your knees like you just came outta a sentra-fuse (SP )

want a rabbit hole you can't get back from, find some Physicists  papers on functional MRI