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Japanese tube amps?
Surely, you mean Chinese? Japanese amps usually are SET (Single Ended
Triode), tend to use extremely obscure and insanely expensive parts
like hand-winded silverwire output transformers, capacitors with a
dielectric of moonlight (or a derivative), and resistors with
unpronouncable names, that tend to change their value when soldered.
But an intended change, you will note ;-)

The Japanese have many factory built and kit amps to choose from but
most are low power, very expensive, and a challenge to order from
outside Japan. Most Japanese vendors DO NOT speak any other language
and are not overly interested in dealing with foreign buyers. There are
exceptions.


And more to the point: most Japanese amps I know of, never leave
Japan, are mostly made by fanatic DIY-ers, and more often than not, a
one-of-a-kind job.

That's not a judgement of their sonic qualities, BTW.


But the Chinese.........ah!
They churn out millions of affordable tube amps, just to satisfy the
unsuspecting Western customer, mostly without any regard to quality
control.

Not all, but most. And don't be surprised when "your" company vanishes
without a trace within the warranty period.............


I happened to own the ES11 as well, and it is an excellent speaker to
drive with a high quality tube amp.
To separate the wheat from the chaff wrt. Chinese tube amps is a
mission impossible, there are simply too many of them, and rumours go
that quality varies within the same model, sometimes even complete
different circuits and tube types are used with the same name and
model #.

The Chinese are terrible vendors in terms of QC and consistency.

So, get yourself a nice KT88PP trioded amplifier, or, even better,
build one yourself, so you know what quality you have.

For the power he will need several pairs of them if trioded.

Key are the output transformers, and triode strapping of the KT88s.
All the rest can and may vary, but those 2 are most important to get
the most out of your speakers IMHO.

I can't tell which country you're from, but if you can lay your hands
on a pair of Amplimo/Plitron output transformers, you're halfway
there.


The transformers you mention are toroids. Toroid transformers are not
a good choice for tube amplifiers, at least as they are normally built.
They are not new, GenRad made them in the 50s. The problem then was the
problem now: saturation of the core by any hint of DC offset. A split
core is not the answer either, as they then get large and even more
expensive. Either EI or C-core is far better in most cases.

First rate push pull output transformers should be capable of
sustaining their rated power output and THD with a 10% quiescent
current mismatch at 20 Hz. Decent ones will tolerate 5% at 30 or so Hz.
Now that Partridge and Harrison are long dead, decent is the most to
hope for.

If you can't or won't build a tube amp yourself, find a knowledgeable
hobbyist to do it for you.
There are still many of them out there, and most build amps just to
put them on the shelf with all the others.
They're probably very happy to sell you one, or to build one for
actual use by anyone other than themselves ;-)


Most service organizations will not look at homebuilt equipment. If
you are a nonbuilder and want a tube amp, I would buy a new one from a
manufacturer or a restored vintage one of good make from a dealer with
a good reputation and some warranty. Used DIY equipment has no value to
dealers and can't be insured.