There is absolutely no danger of a nuclear meltdown or any other untoward incident, if you insist upon trying the 100-ohm load option. At 100 ohms, using a cartridge with a 30-ohm internal resistance, a good fraction of the voltage output of the cartridge will be diverted to ground and never make it into the phono stage. In other words, there will be an apparent loss of total gain, compared to using a load of 475 ohms or anything above that. If the gain of your phono stage is marginal for the output of your cartridge, you will not like that. In addition, the response of the cartridge will not be perfectly linear at very high frequencies; there will be a roll-off that may or may not occur within the audio frequency range. Whether you will hear that or not is a matter of your hearing acuity and etc. Some folks deliberately "cure" a cartridge or the system of excessive brightness by deliberately selecting a relatively heavy load (low input resistor value). I personally would not ever do that; I'd try to start out with components that don't irritate. In my already stated opinion, you would be best off with the 475, 1000, or 47K ohm options.
