don't have answer but the same problem here with 26c . my input signal is very weak and when i turn the knobs open past 2o'clock i get a lot of noise , also when using the headphones.
I checked impedance of microphone an adio-interface: 310 ohm for shure SM57 and 1.6K ohm fore the presonus studio 26C, that shouldnt be the problem.
any tips ?

greets!

Are both of you using microphone cables (xlr on both ends)?

Also note that those mics are close-proximity microphones. They’re even less sensitive than an SM58 so the sound source (instrument or vocal) should be well within a foot from the mic.

Hope that helps

thanks for the quick help!!!
i am using an balanced xlr to jack cable for the mic. maybe this is the fault ?( i just ordered a cable with xlr on two ends.)
i am recording a saxophone. so to here myself back trough the headphones, i need a lot of gain ,i tested a bit with the distance and as you stated a small food away from the mic is the best result.
still the level of the signal is relatively low not enough for recording... and still a lot of noise.

thanks already!!