Question MM / MC

Aug 1, 2019
Hello! I bought a Denon DRA 75VR amp and it has a MM/MC switch on it. I found out that if I turn it to MM, which by the way is the type of cartridge I have, an Ortofon 2M Red, the speakers hum more than on the old amp. I checked and the turntable is grounded. However when I switch it to MC, it’s quieter. My question is if I can use it in MC mode. Will it cause any problems with anything?
Try it without grounding the turntable. Sometimes it's quieter that way.
Depending on how much additional gain the MC setting has you may be able to overload the input causing distortion. This won't depend on how loud you are playing the record and can damage tweeters if the volume is high when it happens.
By raising the gain in the phone preamp you are reducing the gain needed in the line stage. If you get hum when playing line level inputs then the receiver will need to be repaired to replace aging parts and maybe bad circuit traces. Not cheap so replacement would make more sense.