> half the power rating (1.25w)
Actually says 0.25, one quarter Watt, which is indeed half the rating of their higher-price line.
0.25W or 250mW is +24dBm. On the face of it, a respectable rating. 12VRMS in 600Ω, which is more than most op-amp chips can touch.
But audio power ratings can be funny. It depends a LOT on what low frequency you need full power at. Look at their "budget-price 10 Watt" 25V/70V speaker line-match transformer. It is the same size (a hair smaller) as the 0.25W line transformer. This actually makes sense. The 70V speaker-tranny racket is large and competitive. The low-price model, any maker, for the last 70 years, will get pretty soggy below 150Hz. For speech and low-fi music below the maximum power, the amplifier must strain to drive all that weak inductance on the line, but it does work well enough to get paid for the job (wiring dozens or thousands of cheap small ceiling speakers in a large office or factory).
So if this core is good for 10W at 150Hz, it is probably good for 0.1W at 15Hz, and the 0.25W rating may really be valid near 20Hz.
To my eye, this looks OK for a mike-amp output nominally delivering +18dBm peaks, normal level below 0dBm. It looks small for a Board Out transformer, rated to run at +8dBm with peaks well over +20dBm and all at lowest distortion.
Also as ed says: for $5, you don't get the magic-alloy core. Distortion would be lower with fancier iron-stuff cut with nickel and other costly metals. But since half the uses of trannies around here are for "iron sound", this "lacking" may be exactly what you want. The plain core will give a bend in the bass at modest levels, and the small core may add extra bentness at some level that you might be able to get from a hot chip or discrete output.
One thing: if the transformer could have zero primary resistance, and you drive it with a zero-impedance source, distortion is nearly zero. And these trannies have very low insertion loss, suggesting quite low primary resistance. To a point, driving them with an op-amp (zero ohm source) gives very low distortion. Problem there is that the low inductance gives a falling impedance in the bass, so at some frequency and voltage the transformer sucks more than the 40mA or so limit of the op-amp. Distortion will be gross. (It may be musically useful.) For attempted low-distortion operation, you could need 100mA peak drive. For funky higher distortion, you should pad-out the op-amp with 100-600Ω before the transformer, so the amp does not try to force the nonlinearity out of the core.
The 600:10K 0.25W, used backward, might make a usable 1:4 mike-input transformer. It has zero shielding so it will suck up all the humm and buzz in the room. You might get away with this plus a power transformer at opposite ends of a 17" rack case, assuming the boxes above and below don't have their power transformers on the mike-tranny end of the box. FWIW: I have an unshielded mike transformer, on a dynamic mike 20 feet above the stage, up in the rafters of the concert hall, laying among power lines and dimmer-lamp cables. I put it in a $1 iron junction box I got in the electrical section of the hardware store (get a cover-plate to enclose the box). This is our backstage monitor system, so the talent knows when their act/piece is coming up and they should get ready. I don't hear a lot of hum or buzz in it.
None of their audio trannies are rated for DC current in the winding. Being plain iron interleaved, they can take a small amount of DC, like the offset voltage of an op-amp. But they won't work as Neve single-ended 2N3055 outputs. You might be able to "do it" with one of their power transformers, but that is all wrong for Neve-style thinking.
