Another question on transformers

[bpucekov]

Please a little help from the transformer guru.
What transformer to use to convert the headphone output from the laptop to a balanced mic level signal?
I think the impedance and turns ratio.
Thanks in advance
Puc

 

[CJ]

you want stereo or mono?

do you have a line input also, or just mic?

maybe this:


- 1/8 to 1/4 stereo adapter
- mono 1/4 inch cable
- DB-1 direct box
- XLR to 1/4" TRS Connector

do you want to wind a DB-1 transformer?

that would be about 3450 turns pri and 300 sec for a 11.5:1 ratio,

on a 25 EI core that will require very small wire on the pri, like #46 or smaller,  :

at 10 volts max input, that will be about 9 kgauss, so a 50/50 core would be about right,

that will give you about 400 henries and 3 henries at 20 hz,

but you have a volume control on that laptop, so if you crank it down to 200-300  millivolts out, you can drop the turns ratio way down to about 2:1 which means a lot less turns,

so you would only need about 600 turns instead of 3450, which means bigger wire and easy to wind,

the core would be loafing at 1 kgauss due to the big drop in voltage level, so you could use 80 NI to get the pri inductance up a notch,


henries would be about 26 pri and 6.5 sec, this is a Z ratio of about 2400:600 ohms,

pri DCR would come down from 3k to 280 ohms,

UTC A39 is a kickazz DI xfmr and cheap if you find one on evilbay,

600:2k so you use it backwards,

you should use faraday shields if you are running long cables,

 

[PRR]

If the mike amp is any good, this will work:

 

[emrr]

I like PRR's plan.

 

[CJ]

also, you can adjust certain sound parameters by going to

control panel>hardware and sound

if you have windows,

Mac probably has even more options,

i bet there are cables with small transformers built in as a lot of DJ's are taking their laptop into the club and saying "i can play any song in the universe people, just put a dollar in the tip jar" as they load up another utube file,

busking has never been so easy, use to have to sit out in the alley with the geetar and keep an eye out for the panhandle cops,  8)

 

[MagnetoSound]

Most clubs these days are equipped with a DJ mixer that can receive a signal from just about anything.

Most DI boxes these days are equipped with pads, and can receive a signal from just about anything.

A cable with a 3.5mm stereo plug to twin RCAs or jacks is usually all that is required.

 

[bpucekov]

Thanks CJ for the detailed response.
Thanks to everyone for their efforts.
PRR
Must be, transformer balanced. It is a specific case, but I can not for the moment to talk about the details because it is possible that it turns into a commercial product.
Puc

 

[CJ]

no problem bpucekov!

stay tuned, i am going to take apart the UTC A-39 and get more winding details,
should be done by tomorrow,

this will be the whole meal, not just the desert, 

will post a thread,

 

[CJ]

bpucekov , if you are still around  we took apart the UTC A-39 which when flipped around makes a nice sounding DI transformer,see the info below in the pic,

i need to grow a longer arm so i can pat myself on the back, 

why?  my guess on the 25 EI core was pretty close, the 24-25 EE core has the exact same dimensions and the exact same inductance coef, i guessed 600 turns , the utc has 1090, so the Henries were off a bit but still in the same ballpark.
EE lam has a little less leakage inductance with the self shielding geometry as it limits flux fringing, self shielding by the copper windings keeps the lines of force from spreading out like they do at the EI gap.

if you need a different ratio just tweak the turns.

 

[bpucekov]

Thank You CJ
You are THE MAN
Puc

 

[CJ]

Great!

now can you find my long lost Yugoslavian girlfriend who defected to the beaches of Koversada? She can sing like a bird.

here name was Olga, left new years day, 2007, she used to look like this>  ;D

 

[bpucekov]

No problem, as soon as I see it, I'll tell her that you're looking for.

By the way

"If I can't fix it, I can fix it so nobody else can!"

Exactly the same thing, told my professor from the electronics in high school, after which he gave me to fix his television.

Puc

 

[CJ]

http://www.groupdiy.com/index.php?topic=51666.0

here is another DI print, 1:11,