Output terminology 1:1 or 1:2 question

Yes, I think so.
I picked up a pair of the JENSEN JE123-s transformers for a pair of CAPI-GEAR 312 DI's.
Just need to figure out the wiring.
Probably need to contact Jeff.

Yes, you can double the output voltage, but the current will half.  You need to be careful about the impedance that the transformer will see on the secondary because while you increased the potential voltage, you might not actually get the full voltage if the load impedance is not high enough. 

Gain stays the same. The output operating level changes from lower voltage, lower impedance to a higher voltage and higher impedance.

t types will get you in the ballpark. but H -pad is the way to go for absolute precision and offers the lowest input noise because its the only attenuator circuit that offers impedance matching in its design. Its cousin the O type is a variation of the H-pad is good but only really applicable in transformer to transformer coupling.

Whats a DOA?

Of course it does. Gain is by definition a ratio, for audio we’re talking about voltage. For a preamp, the total gain is the output voltage divided by the input voltage. If you change the ratio of the output transformer from 1:1 to 1:2 your net gain goes up by 2x or 6 dB. Remember gain in voltage is out/in but in decibels it is 20*log (out/in). For your example of a 40 dB gain amplifier, 40 dB is close to a gain of 100. Adding a 1:2 turns that into a gain of 200, which is 46 dB.

It’s no different than gain changing if you change the ratio of the input transformer.

Most of what this guy is saying is addled nonsense.

see what i mean? nonsense.

doesn't matter what datasheet you have if you don't understand what it says.

the log of 2 is 0.3. 20 times 0.3 is 6 dB. a gain of 2 is 6 dB. you don't know what the fuck you're talking about.

sure, use more terms you vaguely understand. quit wasting people's time acting like an expert.

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I think you might have a bit of misunderstanding about input and output impedances.

Also, there is no reason to use a JT-11P as a line output. It is made to be an input transformer. Jensen also makes other mic inputs for a jfet input op amp - the 13k6 or 115 will not have the right ratio for lowest noise with a jfet input amp.

Modern designs are bridging - the output impedance is “much less” than the input impedance for maximum voltage transfer.

you want your output impedance low.

I’m sorry but again I think you’ve got some things mixed up.

Resistors have thermal noise that rises with resistance, sure. A 20k resistor at room temp is like -110 dBu or so just from its own self noise.

There’s always a noise floor in every circuit.

For lowest noise the amp should be coupled with a transformer to the mic that presents the optimum impedance. This is different for different amplifiers. Since BJT have lower impedance than JFET input amps, they have different current and voltage noise, and need different input transformers for lowest noise. That’s why jensen and others make so many different ones. Every circuit has an optimum source impedance for lowest noise.

Gapped vs non gapped is just whether or not a transformer can tolerate DC current flowing through its coils.

Matching is not better or worse. Matching gives optimum power transfer. In audio we don’t care about power, the voltage is the signal carrying medium. In fact, we want less current to flow, so we can drive higher voltages for a given voltage rail. There is a reason all modern audio devices are bridging. This is for maximum voltage transfer. Matching impedance also has an inherent 6 dB loss, which inevitably raises the noise floor.