I am sorry for the delay but the transformers must have come from China!
See, having banged my drum saying an XLR DI out on an amp should be balanced and at mic level (shall we say -40dBV 10mV?) and really should be transformer isolated I thought I should put my money where my mouth is? A whole tenner! That tenner amazingly bought me TEN 1:1 transformers, wee things, 14x10x5mm pri and sec resistance around 140 Ohms (will do pikkies later)
I generated 1kHz at neg 6 in Samplitude (see wavgen) and you can see the harmonics are almost 100dB down for the third and falling and no second harmonics.
That signal was passed through a ZED10 mixer from the laptop and some 0.5V fed to a traff primary. The traff output was loaded with 6k8 being a little less kind than the normal 10k.
Sec' out was recorded via NI KA6 into a desktop and you can see the resultant spectrum
'Oribble innit! Well not really. Third is the highest harmonic and that is 60dB down on 1Khz. For such a cheap transformer I reckon that is not at all bad? Yes, distortion at 100Hz is going to be worse (my next test) but consider, if use to deliver a MIC level output the signal level will be a good 30dB below half a volts and thus distortion proportionately less. ANYWAY! Bit o second harmonic adds 'warmf!"
I hope to be able to do more tests. Distortion at lower frequencies at 'mic' levels and, if I find the time and energy some for of distortion device driven frm an amp dummy load.
If anyone this side of The Pond wants one to play with I can donate four* say. Just PM an address. No charge.
*I meant one EACH! (top pic is output)
Dave.