Transformer Question (usability)

sr1200 · Mar 31, 2018

i "rescued" a pair of transformers from a busted up preamp that i cant fix (cant find pots for it anywhere). one side reads 27.5ohms the other side reads 275ohm (10:1)? question is: these impedances seem very low compared to what i've used in the past for mic/di applications. are they usable for anything (like maybe a pair of cheap di's?) or are they pretty much garbage?

AusTex64 · Apr 1, 2018

Photos please?

rackmonkey · Apr 1, 2018

How are you measuring them? Those values sound like DC resistance, not impedance.

rock soderstrom · Apr 1, 2018

I guess that your transformer has more of a 1: 3 transfer ratio. The impedance is in square with the transfer ratio. Rackmonkey is right, you are talking about DC resistance, so this is just a rough estimate, reality could be different. Only measuring with a signal generator and oscilloscope will show you the truth.

PRR · Apr 1, 2018

> one side reads 27.5ohms the other side reads 275ohm (10:1)? question is: these impedances seem very low compared to what i've used in the past

What readings have you seen in the past?

The DCR is normally about 1/10th of the intended audio impedance. So about 270 to 2.7K. This is well within the range of dynamic mike to BJT working around 100uA. Or '5532. Or for hi-level mike to a tube.

sr1200 · Apr 1, 2018

The DCR is normally about 1/10th of the intended audio impedance. So about 270 to 2.7K.

See, thats good to know. I was referring to what impedances are shown on the tx specs (like 150:1.5k)

Any suggestion for a quick and dirty project to use these on?