OTL All American Five? (or Ten) - diyAudio
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Old 28th May 2012, 10:53 PM   #1
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Smile OTL All American Five? (or Ten)

I don't plan to actually try this but am curious to know if it would work.

How about a tube amp that had no output transformer but also has no input (power) transformer either...

Say, Ten 12B4A tubes with the heaters in series could run directly from line current. (I dont know of any common series voltage regulator type tubes other than this with 12 volt heaters) And that could be 5 parallel circlotrons, so here is my question: Would full wave rectifying 120 volt line current twice count as two independant floating power supplies for the circlotrons? So could 8 SS diodes and 10 tubes create a tube amp on the cheap?

Or if one filament transformer could be allowed, say a big 6 volt farm battery charger transformer, then I guess 6080 or the like would be better because it would take much less of them for the same power. However even twenty 6080s per channel with heaters in series running directly from line current could still be cheaper than some high end output transformers I have seen for a non otl. Thanks, Austin
Old 28th May 2012, 11:01 PM   #2
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It just occurred to me that a microwave oven transformer ran backwards might make an excellent filament transformer depending on the winding ratio. They are about 20:1 I think.
Old 29th May 2012, 04:23 AM   #3
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The transformer provides isolation from the mains grid and is your life insureance NEVER EVER build what you propose !!!!!!!
Old 29th May 2012, 06:53 AM   #4
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After thinking about it, I realize that two floating power supplies can not be easily made from a single 120 volt source. And then I realized it can't be made with 220 volt source either, even half rectified off of the two poles because of the common referance point. The only way to make the All American Otl is to use another topology other than circlotron, like a variation of Futterman OTL . It is possible then at least this way, if I use 240 volt mains from the dryer outlet or straight from the breaker box with a makeshift extension cord.Click the image to open in full size.

The neutral wire is the ground.

As little as 40ma across your heart can be lethal to a full grown healthy adult. A transformer is not really going to save your life if say, you take a direct current from one arm to the other, however the point is to not get shocked transformer or not! There have been people that have died from picking up a 12 volt battery by the still connected frayed copper terminal/cables. The impedance of your body is quite low when directly coupled to your blood which is as salty as sea water. How long have people successfully used All American Five radios? According to the internet it appears there may be people that still do use them.

I myself think the coolest otl topology is the circlotron tho and I propose the cheapest way to implement it is with the use of two cheap inverters from that cheap tool place. It could be filtered with the right combination of rc and powered by a single 12 volt deep cycle battery, the fillament supply could come from the same charger that keeps the battery charged. A circlotron needs two separate tubes and there is no reason the 6 volt fillaments couldn't be in series right?

Last edited by Austin Translation; 29th May 2012 at 07:08 AM.
Old 29th May 2012, 07:35 AM   #5
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So what happens when someone turns the wallconnector the wrong way or changes it without making notice of live and neutral or the elctrician installing the outlet was tired in the morning ????

Abrakadabra you got a live ground !!!

3-prongs and transformers is a good life ensurance.

There is a scary amount of energy in an OTL without adding the extra touch of the mains grid.

Measuring on mine i slipped with the probe and shorted the cap bank KABOOM melted probe and ringing in the ears, wife heard it from the floor under and came to check if she could cash in the life ensurance.

And shure anything above 50V and 30mA is to be considered highvoltage.
Old 29th May 2012, 07:43 AM   #6
poynton is offline poynton  United Kingdom
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Banned Topic

This post has been reported to the Mods as it is banned under forum rules to discuss any direct connection to the mains supply.
If it ain't broke, break it !! Then fix it again. It's called DIY !
Old 29th May 2012, 07:57 AM   #7
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I was unaware of the rule for discussion of mains connected supply. What forum would I be able to discuss this in?
Old 29th May 2012, 08:12 AM   #8
SY is offline SY  United States
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Direct mains connection is DEADLY DANGEROUS, not just to the constructor, but to innocent people who are unfortunate enough to touch the device. This has been discussed numerous times on this forum and, because of the extreme danger to others (the All American 5 killed people, which is why it is no longer legal to sell), forum rules prohibit discussion of such circuits.

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Old 29th May 2012, 08:17 AM   #9
Salas is offline Salas  Greece
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No forum to discuss this. Direct connection to high energy is lethal practice and illegal. Just ask any electrician. There is a clear rule in DIYA for not allowing such threads. This means its a locked thread now. Safety first. Regards.

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