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help me build an output transformer

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A

AudioGeek

Member
Joined 2004
I am trying to increase my knowledge in transformers. One way is to try and use this forum and all the helpful folks.

My goal is to try and come up with an transformer design then build it myself.

My goal is to build a 1:1 output transformer. 100mH primary Inductance and 1 ohm or less primary resistance. probably bifilar wound and oh yes 3A dc primary current.

Is for a SS Class A amp... yeah i know its SS and this is a tube forum, but i thought that the transformer winders probably hang out here and not the SS one. lol.

I am looking for the process / steps to determine core size, number of turns, wire size, and gap size.

I will purchase the core from? and wire from? and wind myself.

Please anyone want to help me?

Thanks!
 
GloBug

GloBug

Banned
Joined 2011
....need more input.
 

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C

ChrisA

Member
Joined 2008
AudioGeek said:
I am trying to increase my knowledge in transformers. One way is to try and use this forum and all the helpful folks.

My goal is to try and come up with an transformer design then build it myself.

My goal is to build a 1:1 output transformer. 100mH primary Inductance and 1 ohm or less primary resistance. probably bifilar wound and oh yes 3A dc primary current.

Is for a SS Class A amp... yeah i know its SS and this is a tube forum, but i thought that the transformer winders probably hang out here and not the SS one. lol.

I am looking for the process / steps to determine core size, number of turns, wire size, and gap size.

I will purchase the core from? and wire from? and wind myself.

Please anyone want to help me?

Thanks!
Click to expand...

Physically building the trandformer is a lot of work but given enough time and though and preparation and building some jigs you could do it

Designing one is harder and you should expect it to require more then one attempt. I don't think anyone builds a masterpeice on their first try.

The FIRST step is to aquire the equipment to skills to measure a transformer's performance.

At first you think designing a transformer is easy. Just remember that impedance ratio is the square root of the turns ratio. But there are many secondary effects such capacitance between the coils and also between wires in the same coil and leakage inductance. This is where the art comes in as you have to trade off one bad thing for another. No transformer can be perfect you you need to design the "least bad" one you can

I good reference you can download is the old "Radiotron" book. There is a chapter on transformer design. The author starts with a simple overview and cover design using just turns ration. Then he starts over but includes some other factors. It continues adding more and more secondary effects.

http://www.tubebooks.org/Books/RDH4.pdf

There are some more advanced books on transformers on the same web site tubebooks.org - Vintage info from the age of vacuum tubes
 
A

AudioGeek

Member
Joined 2004
i have contacted dave slagle... he actually made some transformer volume control autoformers that are very nice. He just uses nickel soo... he didn't want to do it.

please tell me what data is needed to start a transformer... i know that it is challenge to build these but i am ready for the challenge.

i found these sites:

se-output-trans-calc-1

DIY Simple Output Transformer

Error on Page

and i have a copy of RDH4.

I would even be willing to pay someone to design a transformer then build it myself.

I have a signal generator, DVM, Oscilloscope etc.

Thanks!
 
V

v4lve lover

Member
Joined 2010
to get started and take some measurements before you actually spend money
you could salvage an old Xformer core lets say 200 watts find some solid core wiring rated at amperes lets say 5 take all E and I laminations apart and wind the bobbin 1:1 whit just solid core wire or use multi strand :D that will increase your freq response considerably just like multi strand wire in SWMP tranny's

then put the transformer together E laminations on one side I's on the other cardboard as an air gap might use tie wraps to bind it all together then see or it gives the desired results

just my 2 cents , damm nice expression :rolleyes:
 
kevinkr

kevinkr

Administrator
Joined 2004
kta-hifi.net
Paid Member
Yvesm said:
Nah, nah, nah !

You DO NOT need a huge air gap for 3 Amp because you DO NOT need many turns to acheive expected primary impedance !
Remember: DC field is proportional to the product of the current with the turns number.

Yves.
Click to expand...

:up:

Take a look at those C-cores I linked to a couple of pages back, I would think something alphacore makes would be suitable - end result should be good with a little experimentation. A bi-filar winding would probably do the trick.
 
Yvesm

Yvesm

Member
Joined 2004
dissident-audio.com
kevinkr said:
. . .
A bi-filar winding would probably do the trick.
Click to expand...
Probably !
I did something like that for a Nemesis clone wich is a 4:1 winding 4 bifilar windings.
Then, pick one wire from each winding and tie them in serie to form the primary.
Tie the four remaining in parallel to form the secondary.

You just need a single section, but what is missing for calculate is the power you're atttempting to transfer and at wich frequency.

Yves.
 
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