In my, what is beginning to seam like a never ending, simple decision to which amp to buy, I asked NAD a question regarding their wattage rating on their C272 power amp. Now I’m even more confused. Before sending them a responce, I was hopeing one of you guru’s could help me tailor it better. I’ve found that while directing a technical question via email, I need to be specific. Tech’s like to keep it short and simple.

Their response has me baffled. What do you think?


Submitted Category: Power Amplifiers

2005-04-27
11:23 pm C272 wattage rating
Good day,

I am confused with regards to your watt rating on the C272 power amp. You’re description states 150 watts per channel at 8/4 ohm. I do not understand this. I do not understand why the wattage rating stays the same with less resistance. I read the section regarding your power drive technology, but still, this is contrary to basic electrical theory. With a reduced resistance, wattage should increase.

The reason I am asking, is I have a set of 4 ohm speakers that are rated at 400 watts at 4 ohm continuous power. I want to purchase a new amp / pre amp combination for these speakers, and would like to give NAD a try, but the 4 ohm rating concerns me. I also understand that NAD is very conservative with their power ratings and has a respectable amount of head room and current, but again, please educate me regarding your wattage rating.


2005-04-29
9:09 am re: C272 wattage rating
Thank you for your recent request via the NAD Electronics web-site. I spoke with technical services regarding your questions, and here is their input:

Power Drive works like this:

Power Drive works by constantly monitoring the following conditions
1.Load impedance
2.Power being delivered to the load
3.The heat sink and ambient temperature.

This information is fed to a simple “Analog computer” which controls the power supply between a high voltage and low voltage level.
Switching of the power supply is done on the following basis:

• Load impedance is <4 ohms then switch to low supply. Load is 8 ohms then switch to high supply.

• Heat sink temperature is high switch to low supply.

• Ambient and heat sink temperature is high then switch to low supply.
The switching between two supplies is done when the above conditions are true over a number of cycles of the signal.

Thus you can see that the power is the same for both resistances 4 and 8 because the power rails are switched.

Best regards,