NAD T973 Power Amp - Power Rating 7x145w or 2x200w

I haven't acually seen any product specifically mentioning it like that... Have you? Any other products actually state that?

This is from the NAD website;

Its feature list includes:
- 7 x 140W Minimum Continuous Power (8 / 4 Ohms); all channels driven simultaneously
- 2 x 200W Continuous Power (8 / 4 Ohms)
- 230W, 390W and 450W IHF Power into 8, 4 and 2 ohms, respectively
- Mono-block, Modular construction
- Differential, Class A input circuit topology
- High Current Holmgren™ Toroidal Power Transformer
- Input gain control for each individual channel
- Gold Plated RCA Inputs
- NAD Soft Clipping™
- 12V Trigger for automated ON/OFF operation

http://www.nadelectronics.com/ht_amplifiers/T973_shortform.htm

Eandylee,

I can't say that I have specifically seen specs mentioned "exactly" like this. However, I went deeper into the NAD website to understamd how the amplifier was designed so I could gain insight into what the specs meant. Please note that although the specs say it is of "Mono-block, Modular construction" they only mention a single Toroidal Power Transformer. Also, if you dig into the specs you will find mention of only one set of power supply capacitors. If this amp was of "true" monoblock design, there wold be separate input transformers and capacitor banks for each channel.

As far as other products are concerned, I am quoting the following statement from Aragon's website:

"In today's multi-channel theater and music systems, the power supply requirements are quite different. The dynamics of modern digital soundtracks can demand huge amounts of power from different channels at different times. One way to provide for that would be to use multiple large power supplies, but that results in additional cost, size and weight. The 2000 Series amplifiers feature a single power supply design that we call SmartPower™. In this configuration, a channel could provide substantially more than its rated output for short periods of time by getting more energy from the power supply while the other channels aren't demanding as much."

Though this quote only mentions "...short periods of time..." "...while the other channels aren't demanding as much." I know that if the other channels weren't used at all then a continous power rating could be assigned to only two channels of the amp, like with the NAD.

Please note that this is only one example of this type of design, and that many companies use this approach in the design of their multi-channel amplifiers. If you want to hear specifically from NAD, I would suggest that you email them directly.

I hope this helps :o)

Eandylee, mostly MCH amps in a single chassis using a single, large powersupply do the exact same thing. The available juice is shared between all of the channels. The idea is in home theather you rarely need all channels driven.

Most seem to design around the assumption that during peak demands (read helicopters, car chases, and explosions) most often only three channels are being driven to the max, the others are mostly idle. It can be any of the three channels, it doesn't really matter.

That way you have a bunch of shared juice on tap without having to overdesign the amp (separate large PSU for each channel, etc). This issue to cost and space savings. else you would just buy 5-7 Krell FPB monoblocs each in its own chassis.

Power ratings are sort of a funny business. Everyone rates them differently. And everyone interprets them differently. Maybe you would be better off comparing VA ratings of power supplies instead? That might give you a better picture of how much balls the amp has. Just a thought.

Thanks guys! very helpful.

Here is another multi-channel amp with similar spec, but it looks like it's not as good(effective) as NAD I guess

POWER OUTPUT (Anthem PVA 7)
# of Channels Driven --------- 1 ----- all(7) -------
Power rating ----------------- 125 --- 100 -------

http://www.anthemav.com/NewSitev2.0/AnthemProduct/PVASeries/PVASpecs/PVASeriesSpecs.html

It means
when listening to movie(5 or 7 channels) = 100W/ch
and when listening to music(2 channels) = little less than 125W/ch.

Only 25% increase, compare to 40% increase for NAD for 2 channel applicaton.

So, whatever their design method, I geuss that NAD amp is better deal in terms of 2 channel application?

I thought it's very natural to provide the 2 channel only power rating, but surprisingly not many provide it like NAD and Anthem.

NAD is known to be very conservative and honest in their power ratings, and I guess it fits my need well, so I'll probably get it after reading some more reveiws and auditioning.