Has anyone compared the EMT 139st phonostage to others ?

There is an Audiogon listing of the TPM-1000 transformers.

One one picture the explanation is given.

I can't upload pictures here a simple explanation:

- both 100% identical transformers are connected in series. (which means input impedance is doubled but this has no effect on soundquality at all)

- the core of both transformers are oriented 90 degrees to each other (hum elimination, once can even do it by ear and hear the difference)

So if they’re in series, then the net voltage gain is a multiple of the individual voltage gain of each SUT? For example, a 1:10 ratio will increase gain 10X at the secondary of the first SUT. Then that voltage would be again increased by 10X across the second SUT, for a total V gain of 100X? Why would that ever be needed? I must misunderstand the hookup.

What would that result in an increase gain of 10x ?

It is a normal series connection, it increases the input impedance!