emt input transformer dissection + u47 transformer links

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ioaudio

Well-known member
Joined
May 11, 2005
Messages
2,087
Location
vienna/austria
this transformer origins from the input section of a portable emt mixer. i don´t know the manufacturer of the transformers,since the the laminations came from the other side of the pond, but the copper wire diameter & shielding thickness has european sizes.

the winding data per coil:

inner layer: primary 3 x 200 (600) turns - 0,15 mm wire, seems handwound.
copper shilding 0,1 mm
outer layer: secondary 3 x 600 (1800) turns - 0,1 mm wire
emtwindings.jpg


used lamination type is 375 UI (the ones without holes in the pictures)
alloy probably 80%NiFe
beside the differences in size you can also see the difference of the alloy.

i unwound the secondary on all three sections of the coil, and counted one primary before i rewound the transformer.

click on thumbs

 
very cool. it is a shame that UI30 lams are nearly impossible to get now, from what i've seen.

that 3 chamber bobbin is neat; don't see those much any more either.

did you note if the primary and secondary windings are wound mechanically in phase or not? as in, does the wire wind on clockwise or anticlockwise on both windings?

ed
 
yes, finding such laminations here in europe - completely crazy. if you can get it, it costs 450 euro/ kilo + vat or even more. 1 kilo makes maybe 10 transformers... but the alloy looks so much different than what you get from magmet. i have to investigate further.

i was wrong about the lamination used in the emt transformer - i messed something up - the Al value of the core is higher than the european 50%, so it seems 80% is used here.

stray inductance seems a bit high - around 100mh

the windings are all wound in the same direction - on both coils. all windings are connected in series.
normal_winding_directions.jpg
 
nah, if we already get into the task of winding transformers we can do better :wink:

normal_mic_out_prototypes.jpg


by the way, i think something got mixed up - the lamination used in the emt - transformer are the ones without holes, and they are available from magmet.
 
crap. i go away for a bit and some joker clips my wings.
.
.
actually, thats one less in a parade of carnage to come.

thanks!

don't sweat the lam shape, worry about the anneal and all that other crap we have no way to test.
 
:grin: no comparrisson with your dissections, this one was real simple, no hacksaw, no compound or any other nasty stuff.
btw, a dissection of a real bv8 would be nice :wink:


here are some bv8 related links


BV8, BV12 transformers
http://recforums.prosoundweb.com/index.php/m/157947/0/?srch=bv8#msg_157947

alloy
Neumann M269c.
http://recforums.prosoundweb.com/index.php/m/1028/0/?srch=alloy#msg_1028

alloy again + inductances
EF86, 6AU6 and 6072 output impedance?
http://recforums.prosoundweb.com/index.php/m/6379/0/#msg_6379

alloy/laminations
lamination material for transformers and chokes
http://recforums.prosoundweb.com/index.php/m/205842/0/#msg_205842

bv8 pics
large transformer U47 and oil caps
http://recforums.prosoundweb.com/index.php/m/50224/0/#msg_50224

bv8 size (30x40mm)
Transformer in U 47
http://recforums.prosoundweb.com/index.php/m/216286/0/#msg_216286

more bv8
please short comment on U47 xformer
http://recforums.prosoundweb.com/index.php/m/228028/0/#msg_228028

copper resistance primary bv8
http://www.neumann.com/forums/view.php?bn=neumann_archive&key=998517835&v=f

transformers in mics discussion
What sounds better: transfomers or transformerless?
http://recforums.prosoundweb.com/index.php/mv/msg/1127/0/0/0/
 
i might hAVE A bv 8.
new stuff arrives every week
massive take apart orgy coming up...
ADM, Quad 8, you name it, i got it.
even a spankin new hs 29 that dr pat is gonna trade me a 217 for since he has a snowball's chance in hell of ever finding a new one.

:green:
 
a neumann c-core trafo - are you sure?
here´s another pic of a bv8
308-2c.JPG


it has two 4-chamber bobbins, and is probably wound similar to the v72 input - probably. i still dont know.
 
dissected by cj in this thread
V67 china mic transformer
http://www.groupdiy.com/index.php?topic=709

cj, it seems you changed your folders on your website: linked pictures in your posts don´t show up any more.

for example:
the link in your post
http://vacuumbrain.com/The_Lab/TA/Gus/gus_1.jpg
but the picture now can be found at
http://vacuumbrain.com/The_Lab/Gus/gus_1.jpg

maybe you could restore your folders for the old structure, it seems easier than editing all of your posts.

-max
 
i am doing some house cleaning at the site, i originally had a TA dierectory in there for reasons unkown, thought it would make it harder for BOTs and other things, but it turned out to be just a pain in the ass, because every time I go to add a pic, its another 15 second wait to jump DIR's.
:oops:
so little by little , 100 posts a night, I will edit things back.
sorry!

plenty of space, gonna get an FTP working if anybody needs space.

cj

PS, that xfmr could be done on a c core, since it's a dual coil layout.
might sound better, less loss, but i don't think you can do a permalloy C core, the metal is too soft to saw?

I will look into this.
maybe we could start building better mic xfmr's than Neumann.
 

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