Here's a pair of German made Beyerdynamic TR/BV 351 015 006 input transformers. These transformers have a single (not split) primary, a single secondary and a shield. The step up ratio is about 1:15 which translates to 200 ohms to 45,000 ohms, perfect for a tube microphone input, or moving coil step up to normal 47K phono stage impedance. The secondaries can also be terminated with high resistance up to about 100K without significant degradation of audio quality. Ampex used these transformers in several of their products (including the MX-10 tube mixer and nuvistor based MR-70 mic preamps) and simply attached the secondary directly to the grid with no other terminating resistor.
I find that with typical microphone levels and source impedances (100-200 ohms) the low end is flat to 20 Hz with low distortion into secondary loads as low as about 40K. The transformers' physical size precludes them being used with line levels, but as mic or MC phono transformers they are very tame and well refined. The top end is excellent. Most high ratio input transformers (even expensive ones like UTC, Triad, Peerless) tend to have a sharp rise above their high frequency spec (20,000 Hz or whatever) which results in ultrasonic ringing that you usually want to damp with a capacitor (or network) across the secondary. These actually have a gradual rolloff around 20,000 Hz, which results in a sweet treble sound even without special termination with a very good 1K square wave response, with very little overshoot or ringing.
These transformers are removed from equipment, but are tested and working. They have approximately four inches of wire, so they're easy to get connected, and I'll also be sure to send you a pair with matching date codes.
The transformers have five wires, the red and black are the primary, the yellow and blue are secondary, the brown is the faraday shield. Red and blue are in phase with each other. If you need any additonal information, please don't hesitate to email. Thanks!
Questi trasformatori non sono in vendita. E solo una web personale dove pubblico un po di cose di audio. Sono cosė facile da collegare che no serve uno schema. 4 cavi, il beyer va collegato tra Denon DL103 e Preamp, sicuramente piu vicino possibile della Denon. Questo due volte, per due canali stereo.