This is a review and detailed measurements of a refurbished and upgraded NAD 2200 stereo amplifier. It was bought by a member, sent to
QuirkAudio to be fully updated and then loaned to me. The work that Peter has done is exemplary. The inside looks brand new! I have repaired hundreds of amplifiers but never seen one this clean! So not only have the inside components been updated/replaced, but a lot of care has gone to cosmetically clean the unit. Peter sent me a long list of parts he has upgraded including reservoir capacitors and such. As a result, I don't know how representative of measurements are of stock units although probably not too far off. Used 2200 go for about US $530 on ebay.
The front panel is nice with an informative clipping indicator:
As you see, you can put the amp in bridge mode (which I did not test) and select whether you want soft clipping on. I left it off as you see in the picture.
During use the protection circuit came on when appropriate and nicely reset as if nothing had happened.
The NAD 2200 uses a dual voltage rail to keep power consumption and heat dissipation low when producing lower power and then upping the voltage for peak power. This is a common technique but usually applied to low baseline power level. Here, 100+ watts of power is provided using the low voltage power supply rail and it is only for power above that where the higher voltage is used. Technique worked quite well as you see later and kept the amplifier cool and happy during my testing.
Amplifier Audio Measurements
As usual, we start with our dashboard view of 1 kHz tone into 4 ohm load at 5 watts:
View attachment 68042
Not bad! Distortion is at or below -100 dB. With noise, SINAD degrades to about 93 dB putting the 2200 well above average of nearly 100 amplifiers tested to date:
View attachment 68043
Notice that the gain is quite high at 32 dB. Common range is 25 to 29 dB with the latter being a "THX" standard. The higher gain increases noise so despite that, performance is as good as seen. High gain makes it a good fit for AVRs for example that produce distorted output well below nominal 2 volts.
Frequency response has a sharp roll off which seems to indicate the output is not direct coupled (DC) as is common today:
View attachment 68044
Or maybe it is on purpose, I don't know.
Crosstalk is very good:
View attachment 68045
As is dynamic range:
View attachment 68046
It is power measurements where the magic of this amplifier comes to life so let's look at that with 4 ohm load first:
View attachment 68047
We can see a kink in distortion when we hit 200 watts as the unit sails past that to produce whopping 337 watts per channel, both driven! Per design characteristics, you can have much more during momentary peaks:
View attachment 68048
Wow, we have one kilowatt of power coming out of this amp in short duration!
Switching to 8 ohm we see similar results as 4 ohm:
View attachment 68050
Sweeping the power test at 4 ohm with different frequencies shows a well-behaved amplifier:
View attachment 68052
You do loose power in higher frequencies but that is fine since music spectrum has lower energy there anyway.
Due to the long duration of this test, the protection circuit likely backed off the high voltage rail, producing lower output levels.
EDIT: adding Lab Input Measurements
Lab Input Measurements
I was surprised that the frequency response was flat and was relieved to see later in the thread that this is due to insertion of low and high pass filters. So here is the frequency response with Lab input that doesn't have such a filter:
View attachment 68105
Response now (in green) as it should be, ruler flat to below 10 Hz, and well extending past the 40 kHz limit of this measurement.
I figured the filters may be adding some noise/distortion so re-ran the dashboard again:
View attachment 68106
Distortion doesn't change but if you look at the noise floor at 20 Hz, it is down by some 10 dB. That improves SINAD a couple of dBs, making the amplifier stand out even more!
View attachment 68107
Zoomed:
View attachment 68109
And signal to noise ratio:
View attachment 68108
Conclusions
Nice to see innovation like this from equipment that is over 30 years old! Shame on manufacturers that produce amplifiers for much less power, more distortion and higher prices these days. No, you don't get a fancy case here and sheet metal is strictly budget category. But you are not going to sit on the amp. The guts are where it matters and NAD 2200 delivers.
NOTE: the output relay on stock 2200 gets corroded and fails over time. There are videos and DIY threads on how to upgrade the relay there to fix the problem. The unit tested here has that fix. Other than that, there are not reports of many other reliability issues even though NAD products are often said to be less reliable than other brands.
Overall,
I am happy to recommend the NAD 2200. I almost gave it the highest honors but given the upgraded nature of the test unit, and the fact that used amps may have issues, I avoided that. But you could have easily pushed me to give it the golfing panther.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Look folks: I need to stay healthy so I can do these reviews for as long as I possibly can. And that means eating the best food there is and that cost money. So
donate what you can using
: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
I bought mine for 369,99 EUR 
