This is a review and detailed measurements of the NAD C268 power amplifier with balanced inputs. It is kindly sent to me by a member and costs US $900 at NAD dealers (not Amazon, etc.). The C268 is built on Hypex UcD Class D amplifier modules so in testing it we will get coverage on that as well. Then again NAD says it is a custom version for them.
The front panel looks good and substantial:
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The unit is nice and light to move around and inside has fair amount of space. Back panel is nice in the way it provides both balanced XLR and unbalanced RCA input together with gain control:
For my testing I used the fixed gain mode to get around any channel differential the potentiometers may introduce.
Speaker terminals are nice and easy to use and naturally the unit is properly certified for safety and emissions. Keep the later in mind as you compare it with any DIY version of the same amplifier modules. With anything with mains input, I highly recommend sticking with products with safety certifications.
In use, the amplifier runs completely cool to touch. Not even above room temperature it seems. It never, ever shut down no matter what I did to it. This is one of the reasons you buy a separate amplifier by the way. These power amplifiers are far more robust than any in any home theater AVR.
Stereo Amplifier Measurements
Here is our usual dashboard where we feed the amplifier a simple 1 kHz sine wave/tone and ask it to produce 5 watts into 4 ohm load (typical for many speakers). This is what we get:
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For some reason the channel in blue has much more second harmonic causing its SINAD -- which is a sum of distortion and noise -- to suffer by 5 dB. There is always some differential between stereo channels but this is a bit much. This aside, performance is above average with a SINAD of 87 dB once averaged (click on graph for larger size):
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Covering the basics, frequency response is very good:
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Crosstalk (one channel bleeding from one to the other) shape is unusual but fortunately it gives is near state-of-the-art performance where our hearing (more or less) is most sensitive:
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Noise performance is very good (much better than its distortion metric):
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You easily clear the CD/streaming content's 16 bit dynamic range at almost any listening level.
Getting fancy and using 32-tones to test for distortion/intermodulation we get what we already seen from the dashboard which is good:
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A power amplifier's job is well, to produce power so let's measure that starting with 4 ohm load:
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NAD rates the amplifier at 80 watts for both 4 and 8 ohm loads which is unusual. Fortunately we are beating that with our 4 ohm load, getting 96 watts.
As noted earlier, noise performance is very good as indicated by how low the red graphs are until distortion sets in and the graph starts to flatten and rise. But then we hit a very hard wall at the end. This is an amp that will sound good until it doesn't. You will instantly know its power limit for good or bad.
There is some hidden good news here though. Let's measure power at 1% distortion+noise both continuous (like above) and burst:
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Wow, many switching amplifiers don't produce much more power in burst mode. Here, we are getting more than double the power to the tune of 230 watts while both channels driven! This means for momentary musical peaks, you have much more power available than our standard non-burst tests show.
Switching to 8 ohms we get what the company advertises:
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All of these power tests are at just one frequency: 1 kHz. Let's now run the same power sweep into 4 ohm load but vary the frequency:
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With class D amps, I expect these lines to have many different shapes and be all of the place. Instead, they land right on top of each other which is an ideal response. If you look to the right before clipping occurs though, you see that at the two ends of the spectrum -- 20 and 20,000 Hz -- power does get limited. 20 kHz doesn't need much power as music spectrum is quite low. But 20 Hz does and loss of power is unfortunate but very common. The peaks at low frequencies last a while due to their slow "speed" (rate of change) which taxes the power supply causing it to run out of juice at lower power levels.
Amplifier Bridged Mode Performance
I usually don't test bridged mode but knowing you rascals, you will immediately ask for it since NAD emphasizes this a lot. So let's reconfigure the amp into a single channel and see what we get:
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Company advertises 300 watts but that is likely at higher distortion than what I use in the above graph. To approximate their performance, let's use the 1% THD+N threshold again and measure again:
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Now we get the 300 watts continuous. And better yet, we get close to half a kilowatt of power for peaks! Nicely done.
Conclusions
The value proposition of the NAD C268 amplifier doesn't look very good at first blush. Just 80 watts per channel for $900? Testing shows while that is more or less the continuous power level, for short duration the amplifier can provide far more power. Combined with the nice and safe build quality, the C268 won my heart.
As such,
I am going to put the NAD C268 on my recommended list.
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As always, questions, comments, recommendations, etc. are welcome.
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