STC 66122X input transformer with Shure Unidyne III (SM57)

Signal path:


Male singing or speaking voice at 2in - STC transformer - Sony TC-D5 Pro with new batteries - Sennheiser HD580


(A phase reversal ie x(-1) XLR adaptor is also used as the particular TC-D5 used phase reverses from mic in to headphones out)


Without the Standard Telephones and Cables transformer the sound is bass heavy and there is hiss due to low signal level driving of the TC-D5 preamp.


By just connecting in parallel to Unidyne III out the 620mH inductance of the transformer primary bass heaviness disappears together with rumble and other low frequency noise. Signal is still low under modulating the following Sony preamp. But mic can be approached closer so signal to noise ratio is actually better.


Then the transformer was connected as 1:2 and then as 1:4. Signal become much hotter with a bit more bass. A big sound. Much improvement in signal to noise ratio.