AK Audio Labs T-20 Step-up transformer SUT

Bought new from AK Audio Labs. They are located in Brooklyn, NY. I used this successfully with two great low-output MC cartridges, the Shelter 5000 and the Zyx R-1000 Airy. Dynamic sense and detail increases nicely with this step-up, with considerably decreased background noise. My setup has recently changed, hence the sale. Nice thick aluminum box. Hi output switch is for >15 Ohm OR >0.4mV. It has a ground connection as well. There are several favorable reviews of their stepups, from Audio Karma, Dagogo, etc.
From the manufacturers online ads:
T-20 Transformers are using Nickle Core and 99.9999% copper wire finished, and potted in the can for the best result. New designed Solid Aluminum chassis. Both of transformers installed in a 13cm (W)x15cm (H)x 20cm (D) case.
"HI" is for impedance(3--15 OHM), or output (0.2mV--0.4mV) MC cartridge.
"LO" is for impedance >15 OHM), or output>0.4 mV MC cartridge.
Specifications
•Power ratio: 1:20 (About 20dB gain, depending on the impedance on the input and output loading)
•Transformer designed: 1+1:10+10
•Input impedance: >3 ohm – 40 ohm
•Output impedance: 47K ohm
•Channel balance: ＜0.5dB
•Frequency: 10Hz-85kHz (-1dB)