transformer question

[enthalpystudios]

transformer question, quick one i hope

what i'm wondering is if a transformer can (and if so, how) invert a signal....

or maybe this is actually getting closer to the difference between balanced and floating balanced.... which i also dont know

anyway a transformer can give me balanced output from an unbalanced signal. I look at jensen app notes and schems, they dont seem to help me see why.

i'm wondering what happens in the transformer when I apply the + and common to the primary and end up with a balanced (presumably the signal and another equal signal of opposite polarity) signal at the secondary. how does the common signal at the primary become an inverted signal for balanced drive???

or perhaps it doesnt and my conception of balanced lines isn't complete

thanks

billy

 

[CJ]

Yes you can invert the signal and it will still be balanced of course.
Most of us invert the signal by accident, and wonder where the bass went.

 

[enthalpystudios]

thanks cj

except, so take a 2503 as an example.....to one winding i apply +/Hi and common, how does common become -/Lo? thats what I don't understand... I think on a CT trafo, I have a bit better of a grasp on it, but i still dont get how that happens

is it just a different ballgame with a quadfilar wind?

thanks mang.... oh btw, my local magmetals guy said no prob about sending me some 625 EI's....got them in superperm 80, is that the one to get? (I hope)

anyway, i'll figure this stuff out eventually, but the RDH transformers chapter can be a bit much sometimes

billy

 

[Boswell]

If you take a transformer with separate primary and secondary windings and apply an alternating voltage across the primary windings, ignoring losses, that voltage (multiplied by the turns ratio) appears across the secondary. The real point in relation to what you were asking is that this secondary voltage is floating, i.e. not referenced to ground or the primary circuit. This means that you can attach any part of the secondary circuit to ground and still have the full voltage available.

If you attach one end of the secondary winding to ground, the other end will have the secondary voltage now relative to ground, and it will be either in phase with the primary or out of phase (inverted) with respect to the primary, depending on which way round you connected the secondary winding. So in that repsect, a transformer can invert, but remember it has been done by shifting the ground reference, not by any active mechanism inside the transformer.

If you were instead to connect a centre-tap on the secondary to ground, the two ends of the secondary would now have an in-phase signal and an inverted signal respectively, but at half the voltage. This is the balanced output that you mentioned.

 

[CJ]

You want 29 ga M6 for the 2503.
I have used Ni, but it's kind of a waste in this application, with no real sonic differences.

I have a ton of 625 EI, but I ran out of wire, so I have some pissed off people out there, but, wire is on the way. (sorry Greg and Jason! and where the heck are you!)
cj

 

[enthalpystudios]

my local sales rep for magmetals said that "we got out of the m6 business a while ago," so I wasn't sure which way to go and he recommended I try the superperm. does magmetals carry something different that I should check out? maybe the 49 is what I shouild have gone with....

anyway, actually just got some 30 gauge mag wire on ebay, about 9 pounds, if y;ou n eed any. when it comes i'll check it out, its old, so i'm not sure if it's still good or not. i'm gonna have to go down to the basement (180 foot long in my apartment building) and twist some quad wire up. about how many turns per foot would you recommend i twist into it cj?

thanks

billy

 

[CJ]

thre or four turns per inch.
you need about 99 feet for a stock 2503, 280-290 turns will get you there.

Temple is where I bought the M6, went thru Ram Sales in L.A.

 

[enthalpystudios]

hmmm yeah have seen you and others mention ram sales.... is m6 significantly cheaper than the nickel? because nickel is fairly pricey.

billy

 

[enthalpystudios]

dude twisting up 99 feet (or thereabouts) of 30 gauge is no joke. the old crap i found on ebay wasnt 30.. its way bigger. i dont know what the guy was thinking. anyway, i got some proper 30 gauge, and finally tonight decided to try and 'twist one up'

disaster. anyway, tomorrow night, i'm going to use a *corded* drill (wont have to run up to the 3rd floor for a battery and back to the basement) oh, and yeah predictable rpm for timing/counting (is that an ok method for counting turns per inch?)

also i need a better way to clamp each end... i'm thinking of just using a vice for the 'non-drill' end.... for the drill side of things, any tips for getting a good hold in the chuck? I kept having troubles..... tried doubling it back, interleaving through chuck and tightening, etc....

anyway, tomorrow night will be magic night in the basement... its handy because its an old silk mill, so the run is really longat least 120 feet, although i could swear someone said it was 180... actually pulling wire down there makes me think otherwise however.

billy

 

[KingKai]

Billy,

When you string out the wire, your going to have one loop and two ends at one end of the string and two loops at the other. Put the end with the two single ends in the vise. this leaves the end with two loops for the drill. Now, insert a "cup hook" in the drill and just "hook" the two loops fer twist'n.

Hope this helps. :thumb:

Peace - Out, Irv

 

[enthalpystudios]

YES!!!!!!

it helps immensely
i was doing it backwards
cup hooks are perfect

i'll try again tonight
hopefully i'll find a vise
thanks again, billy

 

[CJ]

i usually walk up and down the 100 feet twice, holding the wire and feeling for kinks along the way.
by the time i get up and back twice, i am ready to un hook.
note: wire will shrink during twisting, so leave a bow in the middle, 1 foot off the ground if the drill is 3 feet high.
move the drill ( i use a rolling tool box table to put the drill on) a bit closer after you are half way down twisting)

M6 is a ton cheaper than Ni.

but if it's a one time deal...

 

[enthalpystudios]

so hey cj... or anyone, really, but it seems right to ask cj....

i've searched a bunch and cant find much relevant information on litz in transformers.......

how would this transformer differ if it were not twisted litz? just 4 windings. first thing that comes to my mind is tons more winding capacitance and a HF rolloff somewhere. maybe there's something else. i'm asking out of curiosity, not because i dont want to find a vise and twist up this wire and want to know what'll happen if i just wind it up noLitz

seriously, i will actually get around to mounting a vice. i have cup hooks. ready to go.

also, 625EI can be used for all kinds of stuff, eh. i have bobbins for square stack, and am thinking about trying to figure out the 1+1:3.5+3.5 output trannie for the ua 1109 and the 1176revG and la3a outputs. wanna mess with em i guess.

Reading math...... and sinking in a bit.... i suppose it's getting to wire size and how the layers stack that is getting a bit thick for me. stacking and interleaving of layers. the diagrams in the radiotron with all the diagonal lines and everything... come on, what's that about?

 

[CJ]

There is considerable capacitance between the pri and sec windings on the API output.
This is intentional, and kind of ingenious, it lets the high end thru gradually, as the freq increases.
Hopefully, if you have twisted the wire right, you will not get any ripple along the pass band, meaning phase shift, delay, and all that good stuff is pretty linear along the way to 1 mHz.

So why dosent everybody use the API design, since it's so flat?
I guess we want different flavors sometimes.
And, the turns ratio is limited to 1;1, or maybe 2:1, or 1:2.
So not enough impedance to load a tube.

You don't want to run litz wirer in the API.
You want twisted wire. There is a difference in the braiding.
Litz is too expensive also.

Some fiolks have used bi fi or tri-filar wire, it is parallel wires with a bit of insulation/space between the wires. Lots of stray C, and so it works like the twisted stuff.

Layering windings reduces leakage inductance, but raises capacitance.
You get better magnetic coupling if there is not a lot of space between pri and sec windings, thus, if you build a pri-sec sandwich, you get better and better linkage as the amount of layers increase, but your C from pri to sec, goes up becuase the pri ans sec windings are physically closer..

An input might need low leakage, so you might see layering, an output, well, you have power to spare, so losses do to leakage are not as important, wher-as, capacitance might be if your ratio is up there.

One confusing thing I learned about, you don't use bi-filar wire to wind a bi-filar transformer.
What?

Too much capacitance.

You wind two wires at the same time, side by side.
Confused? Me too!
:?

 

[enthalpystudios]

good stuff cj....

and good to know regarding the bifilar.....

like i said, i have cup hooks and a corded drill.

dont make me bring out the cup hooks, i mean business.

 

[CJ]

3 or 4 turns per inch, so 100 feet times 4 times 12 is 100 times 48 is 4800 turns per transformer.

So if your Milwuaukee 3/8 th's variable model #0222-1 spins at 1000, you need 4800/1000 = 4.8 minutes of spin time.

Twist two together, twist two more together, then twist the two sets of two together.

Watch for kinks, feel along the completed wire with your hand.
Kinks can break down the line.

 

[enthalpystudios]

oh by the way, did you see edandersons quote about the urei b11178 tx on that purple vs. g1176 vs. us reissue Poll Thread in the Lab?

[quote author="edanderson"]the core is 46 pieces of 29ga M6 steel, interleaved (no gap) in a 0.65" square stack.

the winding structure is:

1/2 secondary
primary
1/2 secondary

first wind 475 turns of 26ga. the beginning is the start of your secondary, the end gets spliced to the beginning of the other half of the secondary.
wind on a layer of mylar insulation
next wind on 270 turns of 30ga. the beginning is the start of your primary, the end is the finish of your primary.
another layer of insulation
finally, another 475 turns of 26ga. the beginning connects to the end of the first winding, and the end is the finish of your secondary.

that's it. try to wind as neatly as possible, or wind very tight randomly, and it should all fit.[/quote]

how's that sound to you? i need some 26, and then I can try it. aside from the wire and the winding, the core and bobbin is the same as an api output, isnt it?

also... i'm trying to grasp this in schematic form, and the schems are in the la3a, 1176 (rev g schem), and 1109 manuals at:

http://www.jblproservice.com/navigation/Vintage JBL-UREI Electronics.html

on the la3a schem, it looks like both the pri and sec windings are used in parallel.... should be no probs there.

on the 1109 schem, it looks like the pri is in parallel, and the sec. is left split for a couple diff options.... would it be a problem to bring the ends of each sec (as in ed's explanation) out to leads, so they could be used individually, in series, or in parallel?

now on the 1176revG schem, the sec. looks wired in parallel, so again, no probs, but it appears that they are only using half of the primary? with an option to parallel the other half of the primary to the output?

anyway, i guess i'm wondering if there's a good way to split the primary so this trannie could be used for the 1176 rev G, or maybe this isn't needed.....

thanks for the help cj

billy

 

[CJ]

yes, I think Ed measured the core a bit thick, it is probably 0.625, or 5/8 th's inch, which means 625 EI.

You can bring out as many leads as you want, convert them to pvc wire after they leave the coil, so your leakage will go down a tad.

You don't want a big wire putting an air gap in your winding.
This is why designers hated bringing out taps, the more user interfaces, the more leakage, as some companies solder the mag wire to the pvc and then wind over it.

 

[edanderson]

sorry, yes, my bad, i meant to write 0.625" stack. and yes, the core and the bobbin are the same as an api output.

also, i made another typo, i meant 26ga for the primary and 30ga for the secondary. but if you don't have any 26ga, you can just use 30ga for everything and it should be fine. the DCR may increase a bit, but not more than a few ohms, so no big deal.

the recipe is a *simplified* version with only one primary and one secondary. don't bring the two sections of the secondary out to seperate wires, because you need to tie them together to get the 1:3.5 ratio anyway. just make it as described and it should work for the g1176 or an 1109 circuit.

ed

 

[enthalpystudios]

thanks guys!

this is awesome.... now that i look at the gyraf schematic against the ref f/rev g schems i see whats up... took me a minute. i'm going to give it shot with 30... why not.


insulate between layers with wax paper ok?

thanks again!

billy