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Output transformers from China: understanding the market

you seeem to think the chinese are living in the stone age.
Not at all.
They are living in the capitalist age.
Buy low, sell high. Write romantic advertising copy, sell higher.

A fool and his money are soon parted.
And most importantly
The majority of the customers do not have the ability to test or verify anything so if you post up some BS specs most everyone will believe it.
I think that if you have the resources to devote to a full test bench, then you probably have the resources to source quality transformers from a western manufacturer. One that prints guaranteed electrical performance in English.
 
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I can confirm, as a person who travels often to China, and works for a chinese company, that they are not living in the stone age.
They do interleaving, some suppliers even advertise that, show coils etc. But it is true that many do not supply the minimum information required, and sometimes you have to use pliers to extract meaningful info out of the seller.
I bought a while ago a pair of 15W 3.3K SE transformers, at around £25 each, they worked pretty well. I'm sure that established manufacturers like Edcor, Hammond and the likes can do better, but hey, it was a very good value for money. Below the bandwidth measured at 9Vrms/8ohms output in a very simple PSE setup, bang-on -3db @20Khz, as the seller advertised. That's good value in my book:
View attachment 1416776
That may seem like great performance from the listening chair, but a decent American made push pull transformer from the 1950s will give you much flatter response and about 5 additional octaves of frequency response before your -3db point. You may need a test bench to tell the difference but facts are facts.
 
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These cheap 5 watt transformers have a crazy series parallel winding on the primary with a single tapped secondary. I bought one and took it apart just to see if they were better than tie p-t31's from AES. (tubesandmore). they do have more iron.
 
That may seem like great performance from the listening chair, but a decent American made push pull transformer from the 1950s will give you much flatter response and about 5 additional octaves of frequency response before your -3db point. You may need a test bench to tell the difference but facts are facts.
The thread is not about SE vs PP, this is about SE 3.3K OPTs from China (Aliexpress). What has push-pull to do with it?
And you are comparing an SE with no negative feedback, with a typical PP that has plenty of it. NFB flattens the response.
 
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My bad, yes, the transformers were bought from China, via Aliexpress, used in a PSE prototype, no negative feedback. Here is the schematic (including my lazyness for not showing the output winding connections)
SE_2x6P41S_6N1P_InputStage_v2.png
 
An experienced transformer designer will look for clues. One of them is core size. For example, a claim of 10W in SE for a core with an Afe of 3sq.cm, even for HiB is already a red flag. Or a compromise somewhere, like Rdc, little primary inductance giving lower bottom end bandwidth, etc.

For such cost I wouldn't expect layer winding, but more scatter winding with plenty of crossed turns, so a limited lifespan. Core qualities will also be doubtful.
 
Thanks for the hints.
Regarding primary inductance : I noticed that many DIYers tend to overdo things. Bigger is not better if SE-necessary gap not tailored to just what’s needed by output tube current actually needed. Excessive gap (say for 200mA whereas tube set for 60-70mA) means more winding and bigger OT to achieve primary inductance and bass extension = waste of material + more high frequency winding losses or construction challenge and costs.

That’s why I find the Chinese / Asian OT interesting as they’re not excessively large but apparently tailored to tube specificity and actual class A current.

Anyone feel free to correct or confirm this assumption 🧐
 
That’s why I find the Chinese / Asian OT interesting as they’re not excessively large but apparently tailored to tube specificity and actual class A current.

Anyone feel free to correct or confirm this assumption 🧐
If there is complete honesty within the quoted measured parameters, I see no ethical damage. The transformer could be any size possible and tailored by its user's realistic, hopefully, expectation.

But some manufacturers tend to gaslight, and publish incomplete data. It's easy for example to mention the max power output, but at frequency? And at what flux density? And what is the core material?

This is a minimum.
 
Anyone: please list links to interesting SE OT, whether tested or just spotted on vendor sites.
Sorry, I don’t have a link. Look for brand name “Laidys”. Include “Z11” as a search term. I grabbed a pair of 5k into 4/8ohm from eBay for a great price. Just a roll of the dice. The listed weight was encouraging, so I went for it.

For testing, I pulled the Transcendars (worth several times the $) out of my Tubelab SSE and wired up the “Laidys”.

The “Laidys” are now permanently installed in the SSE and the Transcendars will be going in my next amp (TSE-II). No regrets. They are certainly not “junk”, that’s for sure.

P.S. They are ugly. I have covers for mine that I need to install. For now, the shock warning stickers will have to do. Also note, they are larger than they look. They are being dwarfed by the massive 374BX.

IMG_0505.jpeg
 
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