Yes it makes a hum if I put my ear to it. The fan noise is louder than the hum. I would call the temperature cool, not warm. But, I have mine on tile and it's kind of cold and has good ventilation. If yours is warm, maybe you could move it to a better location. I don't notice any difference with the MH vs HPS light when it comes to the hum though.
I had an issue with the Agromax MH bulb they sent. I accidentally flickered the power off and then on quickly, and it was arcing like a welders torch inside the bulb until I cut power. Seemed like a fire hazard. It was very loud and sounded like bb's rolling in a glass. It blackened the inside of the bulb and the circuitry. I was worried about what would happen if I wasn't around and there was a brown out.
Anyway, HTG answered my emails right away at first. They had me ship the Agromax MH bulb back on their dime, and said when they could see the tracking info, they would send me a replacement. I currently have a Sunmaster cool deluxe running I bought from another company, so I'm not able to tell about the hum with the Agromax, and I don't remember it when it was running.
I emailed HTG about the fact it shipped back to them, and I didn't get a response. After not receiving a reply to two emails in a week to HTG telling them the bulb was on the way back, I decided to call. I conveyed my apprehesion about the Agromax bulb, and was told they would send a 6500K non-Agromax replacement. I had to call again because I didn't receive the tracking info as told I would.
I called the second time today, and was told they were packing up another Agromax and pulled it because I was promised a non-Agromax bulb. And that today I would get the tracking info on the replacement. I hope I don't get an even cheaper replacement then the Agromax, or have to call back again tomorrow. It's like my emails get flagged not to read now, and I have to call. I should have confirmed they aren't sending a conversion bulb or something cheap.
If I had to do it again, I would have gotten a Lumatek. Since a backup sounds good, I wanted to get a 400W Lumatek for when/if my Digital Greenhouse goes caput.
HTG has been a headache to deal with after I sent the bulb in for replacement. Up until then, they were great. I wonder what makes them ignore me like they are with my emails. I asked on the phone and was simply told they get 100 emails a day. I refrained from saying maybe you should get more help.
Ok, rant over, phew!