DIY direct box toroid transformer, winds?

[TimWaldvogel]

i am winding my first transformer for fun, and while i already have the specs to wind one for my ribbon microphone, i dont have the parts to test and see if it works, so i thought i would practice in the meantime at winding one for a direct box.

specs
200k primary: 1.5k secondary
12:1 ratio. (all specs of a jensen, but can fluctuate a little

i dont understand how to calculate impedance. most audio products are tested at 1k right? cause the impedance one each side reflects the other so it would reflect the impedance at a load of 1k right? please i need help and its hard to find literature that doesnt overload my brain with information about tube output transformers and such

[Steve Conner]

To quote Carl Sagan, "Billions and billions"

If you want to get into winding your own transformers, passive guitar DI is the worst place you could possibly start. There is a lot of black magic that goes into getting an acceptable frequency response and good loading of the guitar. And thousands of turns of hair-thin wire similar to the stuff used in pickups. Not fun to hand-wind on a toroid.

You can use one of the transformers sold for matching a 200 ohm mic to 50k, turned backwards.

[TimWaldvogel]

It doesn't have to be perfect, I just want to build one for fun. I have 22,24, and 26 gauge magnet wire and a 23mm amphorous alloy core. I can buy different magnet wire, but I really just want to be able to plug it in and see it work. I guess I woul use my 26 guage onthe primary and 22 on the secondary using 12 times as many turns on The primary than the secondary
I need to know where to start though, I am not in a time limit, and I don't expect it to be perfect. Over the course of a week I should have a useable product hopefully. Any help you have as to calculatin the turns myself would be great

[Steve Conner]

Well, what is the permeability, cross-sectional area and magnetic path length of your core?

And use a little geometry. The finest wire you have is #26. How many turns of that can you fit on? (50% packing factor, 50% fill of the toroid centre hole)

What will the inductive reactance of that be at 82Hz, low E on the guitar? Is it the minimum required, about 50k ohms? The Jensen would be more than 200k.

If you ended up with less than 50k of reactance, work back to determine how many turns of what gauge you need to get 50k. My gut feeling is it will work out about 500 to 1000 turns to get anything like a usable sound, but I can't calculate it without the core data.

[J M Fahey]

Well, what is the permeability, cross-sectional area and magnetic path length of your core?

I think finding that will take more than the week allowed for the entire project.
In fact, winding by hand (using a sewing needle?) the maybe 20000 turns required of , say, #45 magnet wire (thickest one which will fit there) will take, say, a Year?.
#26? Forget it.