Neve 1066 style Output Transformer diy

[Spencerleehorton]

Does anyone have any helpful info on winding my own output txf?
I have an winding machine and a quite a few transformers that are a similar size to my other Carnhill output txf.
I have found that i need 28awg Enamel copper wire.
the E to I laminations need to be gapped with electrical tape to stop distortion of the core.

Pri A = 311 windings, wound in reverse (i have read its not essential to wind in reverse?)
Pri B = 311 windings, wound in reverse
Sec A = 524 windings
Sec B = 524 windings

Wind half of Sec B onto spool first 262 winds(then cut), then Pri B wound in reverse(311 winds).
Then wind Sec A(524 winds), then wind Pri A in reverse(311 winds), then solder and heat shrink to Sec B then wind Sec B to finish(262 winds).

question now is where would I put the earth in? And how wide thick etc would this have to be?

I've attached a photo of the txf that I wanted to use as doing a 1066 style output txf but it has two bobbins rather than one, separate for primary and secondary.
Can it be wound with two bobbins or does it need to just be one?
when it comes to winding it, i will try and tension it.

Regards

Spence.

 

[Spencerleehorton]

I have measured the size of the Carnhill txf and these two other txf which i want to use.
My two Txf which i want to wind are the following size:
lams measure 66.72mm x 55.66mm x 22.37
I will make a bobbin for the one that has two bobbins.

Spence.

 

[Spencerleehorton]

Well I have consulted someone who knows a fair bit about this and I'm undertaking the winding.
I'm going to put the screen between the sec B and Pri B windings, does this sound right?
I have some British 30 gauge wire, have taken apart the other txf and bobbin is in tacked.
Going to do the calculations and compare how the results come out.

Will update once done, as I have a way of comparing and testing my results against the carnhill versions.
Full spectrum sweep, a friend has a good setup for testing.

Regards

Spence.

 

[Spencerleehorton]

Here's the old girl!

 

[Spencerleehorton]

Made my own bobbin from pound land photo paper case, which just so happens to be the exact thickness I need!
Going to use PTFE tape to isolate middle of E lamination and use the PTFE tape between windings.

Spence.

 

[Spencerleehorton]

I binned the bobbin I made and used the plastic one.
First attempt I didn't wind tight enough, so second attempt worked out.
I have taken it round to my friends for testing with full spectrum sweep, if I get good results will wind another one!!!

Spence.

 

[ForthMonkey]

Did you re-calculate transformer winding and impedance or you have all info to build this transformer?I want to build my own transformer,too but still i have no idea about how to calculate windings and impedances.

 

[Spencerleehorton]

I will try and show what calculations I have done, hopefully this will help you.

Regards

Spence.

 

[Spencerleehorton]

the txf i wound turned out like **** from the test results, top end was great but bottom end utter poo.
gonna change the lams for some high permeability ones.
first lesson don't try and make an audio transformer out of a mains transformer!!!!!
at least i have the winds right now.

learning at lot!!!

Spence.

 

[Spencerleehorton]

Consulting the SWG or AWG tables I have used the ohms per meter to work out what distance of wire needed on primary, once I have chosen my wire gauge.
E.g. 1000mm = 0.223 ohms / 100 to get what ohms per turn on my bobbin as my bobbins is 25mm

Then multiply this buy 300 turns gives me what ohmage - 6.69ohms

This seems to agree with what ohmage the carnhill is and what wire  gauge it uses.

Spence.

 

[Spencerleehorton]

I feel like I'm learning a lot this week.
I will try and put in basic terms what I have found.
The first thing  that has been difficult to get my head around is the 200ohm/600ohm relationship with the turns ratio.
First of all I thought the calculations had to directly link to these numbers, how wrong it seems I have been.
This along with thinking that I had to replicate the 6 ohm which I tested on the primary of the Neve style output txf has taken the longest to get my head around.
The vital and important info is just the ratio of 1:1.7 and basically whatever wire you use just getting as  many turns on there as possible to aid inductance but it seems there is a trade off with stray capacitance, but I haven't gone on to read into this yet.
There is a calculation for working out the space to fit the wire in and applying tension but I haven't found it yet! But in the meantime using SWG 30 and putting about 300 winds on the primary gets me in the ballpark, 510 winds on the secondary get me pretty close.
I am investigating some much better core material and other bobbins and will be winding and testing a few.
I'm also going to try and do some API style txf as well as I have 8 API-312 mic pres and these would definitely benefit from having a nice output txf rather than the Line balancer IC outputs.
Possibly going to look into doing some for the LA-2A and 1176.

Spence.

 

[Spencerleehorton]

2nd attempt was much better but didn't test well as a had put in screen layer and didn't need to and a few windings had been damage when putting E on bobbin.
Going to wind a smaller diameter on and wind another one using the #30 SWG.
Have got some new info that CJ very kindly gave to me and will implement it all.

Regards

Spence.

 

[Spencerleehorton]

Have made a bit more progress but this is slow learning, so much to take in.

I have my M6 core material and bobbins now, I have made up a version using 0.2mm  and on primarys I got 450  on both and on secondary's I got 752 on each. I know the resistance is going to be higher but waiting for some swg30 to arrive, which is very close to awg28 size wise.
I'm none the wiser yet whether my calculations are correct but I will be consentrating on low resistance high inductance, getting as many windings on there with as bigger wire as possible.
My txf size wise are a fair bit bigger than the carnhills so hoping I can get something as pleasing as them.
Trial and many errors!!!!!!

Regards

Spence.

 

[Whoops]

Nice One.

Where did you get the winding machine?

It would be great if CJ would chime in in this thread!

 

[Spencerleehorton]

I've borrowed the winding machine from a very helpful friend.
One little thing I did spot was about the noise the carnhill txf makes when putting a signal through and turning gain up you can hear the sine wave through the txf acoustically.
When I connect up one I have done it doesn't make any sound, and the top bit of the waveform is pushed down or cut off  a little on the right side?
Anyone explain this please?

Spence.

 

[Spencerleehorton]

HI All,

oh my god!! i've done it, thanks CJ, it was the phase issue, txf sound better than the carnhills now, bit larger but really do kick some butt!!! louder as well. Just need to resolve the issues with the pre amp now and got the neve thing going nicely now!!
ill put some samples together if you guys wanted to compare and have listen, see what you think.

regards

Spence.

 

[Whoops]

HI All,

oh my god!! i've done it, thanks CJ, it was the phase issue, txf sound better than the carnhills now, bit larger but really do kick some butt!!! louder as well. Just need to resolve the issues with the pre amp now and got the neve thing going nicely now!!
ill put some samples together if you guys wanted to compare and have listen, see what you think.

regards

Spence.

Thats impressive,
I keep getting amazed with the things people are able to build in this forum.

So whats your next plans for transformers?

 

[Spencerleehorton]

Well now I've cracked the neve output txf I am going to do the API 2503 output txf.
Once I've done that I do need to try and get my two LA-2A with some better output txf 's.
Only other ones are my 1176 and 1178.
May at some point look into doing some pickup for some people as they have asked as well.

Regards

Spence.

 

[Whoops]

Nice one,
keep us posted on those adventures!

 

[Spencerleehorton]

Hi,

I did do another test against the EZ1290 pre amp i've got and the EZ1290 sounded much better overall.
I have wound another two txf with 0.315mm wire and wound the turns as per the datasheet on the 1066.
Im getting 7ohms per winding on PRI and 16ohms per winding on SEC.
Getting quite a distorted sound now so something aint right?
Im going to wind another input txf to get that right so i can have a hi/low switch.

Spence.