Blue Jinn
Well-known member
Hello,
I have perused most of the transformer impedance/gain postings here and am hopefully on the right track. I have a Shure M68 mixer want to use parts from and the case for another project. Want to re-use the transformers which is only listed in schematic by part number.
Schematic located here:
http://www.freeinfosociety.com/electronics/schematics/audio/shurem68.pdf
There are voltage measurements on the schematic. At the XLR connector .74mV (which seems consistent with a nominal dynamic mike output) and just after C1 9.1mV. If this is correct, my math would say there is a 12.3 voltage gain, for ~1:12 winding ratio? The input impedance for the unit is stated at 300 ohms, so taking the voltage ratio, and squaring it I come up with 300:43k or so for the impedance ratio.
This seems to be a decent step up ratio for a mic pre. Don't know how they will sound, but want to try it out. Thoughts?
Thanks
I have perused most of the transformer impedance/gain postings here and am hopefully on the right track. I have a Shure M68 mixer want to use parts from and the case for another project. Want to re-use the transformers which is only listed in schematic by part number.
Schematic located here:
http://www.freeinfosociety.com/electronics/schematics/audio/shurem68.pdf
There are voltage measurements on the schematic. At the XLR connector .74mV (which seems consistent with a nominal dynamic mike output) and just after C1 9.1mV. If this is correct, my math would say there is a 12.3 voltage gain, for ~1:12 winding ratio? The input impedance for the unit is stated at 300 ohms, so taking the voltage ratio, and squaring it I come up with 300:43k or so for the impedance ratio.
This seems to be a decent step up ratio for a mic pre. Don't know how they will sound, but want to try it out. Thoughts?
Thanks