I need to be able to connect an SM57 and/or and SM58 to a device with the following characteristics. I do not know how to translate from the microphone specs to these specs. I suspect I need a transformer, and I was hoping you could recommend an appropriate Shure transformer.
Nominal input level: +4dBu
Maximum input level: +18dBu
Input impedence: 10K
Connector: TRS (balanced)
(If it matters, the device is an Echo MIA sound card.)
You need more than a transformer. The output of the SM58 is only -54 dBu. A transformer would only boost the signal about 20 dB, so that would not boost the level up to +4 dBu. You need a mic to line amp. See the following links for more information.
Transformers - When do you need one?
How to connect an SM58 to a computer sound card.
Mic and Line Level - What do they mean?