ISO (formerly Tango) is run by three aging gents (I believe in thier 80's) and when they are working there is no talk or interuptions to be allowed. Won't answer the phone, their task at hand takes all their concentration.
Big OPT transformers are harder to get right than a medium powered ones, lower impedance easier than higher impedance. The transformers made by Gery are gems., high end ISO is in another league.
The big trick of an output transformer is the sectioning/interwinding. You want to make the stray inductance as low as possible, and also the self capacitance as low as possible. These requirements will result in very tricky primary/secondary windings arrangement, and serial/parallel windings cross-connected in an unexpected way. I have a PP transformer with two sections, each section 5 layers like P-S-P-S-P, and I tried several options until I got the highest self resonance and tighest coupling. It was not very evident.
For advanced interleaving work one needs to study voltage gradient between layers, hence the resulting capacitance and the importance of capacitance distribution ratio between individual layers. That will alter resonance types and their distribution. Patrick Turner's website is an excellent start for this.
One also chooses individually what kind of HF filter response is aiming for. Optimum interleaving type is different between a SE and PP transformer and also changes for step up, step down, phase splitter, etc. A SE transformer for example has its ground point at the end of primary turns, while a PP transformer has it midpoint. Such info is available at RDH4 and N. Crowhurst, but one has to analyze this in depth and some empirical findings.
Equal Rdc must be guaranteed in all secondary packages. Otherwise a secondary type of leakage inductance kicks in. Cross-coupling solves this issue, but this also dictates the amount of secondary layers. You see, interleaving pattern is dictated by lots of simultaneous parameters.
Ironically, my best interleaving designs are the most sketchy and time consuming for wiring. A beginner transformer manufacturer would get confused wiring them.
One also chooses individually what kind of HF filter response is aiming for. Optimum interleaving type is different between a SE and PP transformer and also changes for step up, step down, phase splitter, etc. A SE transformer for example has its ground point at the end of primary turns, while a PP transformer has it midpoint. Such info is available at RDH4 and N. Crowhurst, but one has to analyze this in depth and some empirical findings.
Equal Rdc must be guaranteed in all secondary packages. Otherwise a secondary type of leakage inductance kicks in. Cross-coupling solves this issue, but this also dictates the amount of secondary layers. You see, interleaving pattern is dictated by lots of simultaneous parameters.
Ironically, my best interleaving designs are the most sketchy and time consuming for wiring. A beginner transformer manufacturer would get confused wiring them.
May I ask you a specific page of the RDH4 where all those information are available?
Thanks.
Page 3 and no mention of this wonderful piece of software? http://www.dissident-audio.com/OPT_da/Page.html
I could even get a station or two using pencil lead or a safety pin on a sandpapered razor blade. Of course, a real Galena crystal worked better, but they were scarce even in the 60's.
Someone who visits these forums might have been seen running around the Motorola plant in bare feet quite often. The weird behavior including swapping out the loud rock tunes for stuff like Crosby Stills and Nash or Firefall usually occurred when laying out complex PC boards though.
When laying out complex PCBs, studying another Language, refreshing my rusty Calculus or learning new software, I can´t stand Music with "words", including my beloved Rock or Blues, so my background music becomes Classical/smooth Jazz/ "chill-lounge" type, all instrumental of course, to avoid unfocusing.
At the other end, when doing simple boring repetitive work such as cutting wood, Tolexing, punching chassis, drilling PCBs, assembling speakers or winding transformers, "something" must fill my brain to avoid boredom or stretch my 10 minute attention span, so I actively listen to something with more content, typically Audiobooks, either human read or generated with text-to-speech converters.
Lately into Michael Connelly´s Harry Bosch police mysteries, go figure.
At the other end, when doing simple boring repetitive work such as cutting wood, Tolexing, punching chassis, drilling PCBs, assembling speakers or winding transformers, "something" must fill my brain to avoid boredom or stretch my 10 minute attention span, so I actively listen to something with more content, typically Audiobooks, either human read or generated with text-to-speech converters.
Lately into Michael Connelly´s Harry Bosch police mysteries, go figure.
I often get severe anxiety when transformer work has to happen, especially a new prototype. Any audio background with human voices help. Rhythmic music is a no-no. But what helps me most is another soul being present in the same room and working on a project. I love enthusiasm especially from young people, but it's getting scarce these days.
I never managed to find a supplier of core laminates that would sell in small quantities for EI core types. Did you solve that?
Not sure how reliable these are, but to be fair, I've not had a bad experience yet with Chinese orders.
https://www.alibaba.com/product-det...433.html?spm=a2700.details.0.0.40eb26e56TbaII
Well, I am in Argentina,so my suppliers can´t help you. :🙁
Yes, of course.
I am quite certain there must be UK equivalents to what I use:
* shops catering to transformer winders (duh!) who might have "small orders" available, maybe a few kilograms, which is acceptable to hobby winders.
They will also have wire and bobbins available, plus spare stuff such as insulating papers,varnish, terminals, etc.
* it is customary here for Technical/"trade/vocational" to have pupils wind at least one transformer, say a 12V 1 or 2 A one or some type which is "useful", who need wire and laminations, if you find and approach one of them they might suggest supplier or attach what you need to one of their next orders.
* there are many shops around rewinding burnt motors, power tools, etc. ; they constantly need wire and might know some supplier who also sells laminations
* you must have some modern equivalent of Yellow Pages or Industrial supplier guides,
My point being, and speaking from experience,"not everything is in the Net", by far, specially old established Industrial suppliers who don´t care much about it for various reasons:
- "everybody knows us"
- "we don´t sell to general public, only Industry"
- "InterneWHAT? .... we use telephone and just incorporated (in 1972 😉 ) that wonderful new Invention: FAX .... what else?"
Meaning: they are out there, but you´ll have to FIND them 😉
If you want to wind your own transformers why you want low grade EI laminations? Buy C-cores. Plenty suppliers in China and all kinds of quality is available there.
Ofc you can find European or USA made cores but they are not so interesting (higher prices, less posebilitlies for high quality cores, more difficult to buy)
I would suggest you start with rebuilding transformers obtained from old equipment.
Then as you gain confidence, modify them.
Finally, new builds.
The lamination quality in the market can be terrible, particularly if the seller knows you are a novice, and it is a small order.
You have a source of winding wire and varnish / similar materials?
Then as you gain confidence, modify them.
Finally, new builds.
The lamination quality in the market can be terrible, particularly if the seller knows you are a novice, and it is a small order.
You have a source of winding wire and varnish / similar materials?
Thanks!
My wife is Argentinian. I know it quite well 😀
Well I’m not really seriously considering winding my own anymore. I just decided to pay up to get them made.
I am struggling with a Spice simulation of transformers at the moment which I might post at some point to as for help.
Yeah that sounds like a better option. It seemed an easy way to start and it’s the kind I’m most familiar with.
I had an old Audionote EI transformer. This is the winding diagram. Because of the vacuum impregnation i am not 100% sure if the isolation between layers and the airgap is 100% correct but it
will be close. The same for the wires, i am 95% sure.
Btw, the 25W is completely nonsens.
Btw, the 25W is completely nonsens.
Last edited:
Hi Popa
Can you give me some winding details?
I would like to make a 5K OPT, 60mA 5W for PL36. SM85c core
It´s mostly right, and close to what I wind for my 50W 2x6L6/EL34 Guitar OTs, but there are a couple "typos"
* Primaries are shown as 900+900 turns on drawing but 1900 total on the wire list. "Pick one" 😉
* 8 ohm winding, 3 x 0.42 mm diameter wires in parallel is "possible"
* 4 ohm winding made out of a single 0.53 mm diameter wire is impossibly thin.
I might believe three such wires in parallel.
* "0.3 mm paper" is most probably Presspahn, not any random paper.
* interleaving shown: primary split in two and secondaries in 3, just to separate primaries, is about the minimum acceptable for Hi Fi, nothing to write home about; is this considered a high end OT?
EDIT: rereading I see it´s not a PP transformer (although by sheer chance turns match what I use for PP, hence the confusion) but apparently a SE one.
They also used the worst handwritten symbol for "8" , now I guess primary halves are 980 turns each, and total is 1960 turns (that "6" is also weird).
Oh well.
Still maintain my comments abut interleaving shown: not bad, at all, but nothing exceptional.
Not even comparable to Mr Turner´s Australian ones.
Just curious: is this one of those silver wire magical transformers?
Last edited: