NAD C298 Stereo Amplifier Review

[restorer-john]

And NAD continue to implement designs where each amplifer is running out of polarity with the other channel (since 1983/4), simply to improve power supply modulation to enable a cheaper PSU, but having little to no effect in the real world and causing a whole bunch of other problems .

 

[PJ 1]

I'm very pleased to see these results for the amplifier I own.

Congrats! It looks like a great product! I'm looking at their M17 V2i and M28 for my living/tv room and their M33 for 2 channel to pare with Perlisten R7ts.

 

[ahofer]

Have we figured out what NAD was trying to achieve with the custom mods? I’m curious what benefit they thought justified the slight deterioration in performance. Reliability? Speaker protection? The world wants to know.

 

[JDS]

That's disappointing, I'm sorry to hear it, good to make people aware of though.

Doing what I can. I would have thought that after Amir's devastating review of the T758 v3 AVR (which I deeply regret buying), NAD would devote some resources to repairing its own damaged reputation.

Not so much, apparently.

 

[Geert]

Have we figured out what NAD was trying to achieve with the custom mods? I’m curious what benefit they thought justified the slight deterioration in performance. Reliability? Speaker protection? The world wants to know.

Like I said, if you already produce your own electronics it's probably cheaper to produce some extra PCB's than to buy finished OEM modules from a supplier. Especially if you, like @restorer-john mentioned, can optimize the design to reduce cost, or if you plan to add some extra functionality anyway (e.g. 12V trigger).

 

[Deleted member 48726]

Looks like NAD has abandoned their "bang for buck" philosophy. Still a nice amp. but expensive.

 

[PuX]

I were you, I would cut back on eating out for a couple of years and save money to get the beautiful master series.

isn't it about twice the price of C298? which makes it more expensive than Benchmark AHB2, which measures better? unless one needs more power, I'd go for the Benchmark at that price

 

[ahofer]

Like I said, if you already produce your own electronics it's probably cheaper to produce some extra PCB's than to buy finished OEM modules from a supplier. Especially if you, like @restorer-john mentioned, can optimize the design to reduce cost, or if you plan to add some extra functionality anyway (e.g. 12V trigger).

So that stuff just supports the variable gain and trigger sensitivity? Seems like a lot.

 

[Kal Rubinson]

I was not a fan of the status LED. On power up, it turns orange. If you hit the power button, it initially goes red making you think there is a fault. But eventually switches to blue saying it is on.

Since I am red/green colorblind and the LED is small, I cannot discern the orange-to-red shift. For me, it is just orange -> blue.

 

[ahofer]

Since I am red/green colorblind and the LED is small, I cannot discern the orange-to-red shift. For me, it is just orange -> blue.

Mine is hidden in a cabinet in the corner of the room and turns on when my RME sends it a signal. So for me it is invisible, just the way I like it.

 

[amper42]

Mine is hidden in a cabinet in the corner of the room and turns on when my RME sends it a signal. So for me it is invisible, just the way I like it.

It would be interesting to use a Kill-a-watt on the C298 to determine how much power it uses while in standby mode waiting for your RME to turn it on. Some of these implementations are not very energy efficient.

 

[Geert]

So that stuff just supports the variable gain and trigger sensitivity? Seems like a lot.

And has a totally different power supply.

 

[dogmamann]

I’m a big fan of NAD amplification and this is a good example of why.

Did NAD in the past had this level of performance before purifi modules ? If yes which amps were those ?

 

[ahofer]

Did NAD in the past had this level of performance before purifi modules ? If yes which amps were those ?

There's an interesting review of the old "power envelope" amp they used to have.

 

[Deleted member 48726]

It would be interesting to use a Kill-a-watt on the C298 to determine how much power it uses while in standby mode waiting for your RME to turn it on. Some of these implementations are not very energy efficient.

Standby power must not be > 0.5 W (regulatory since 2013). NAD C298 Specs.-->

 

[nothingman]

Interesting to go through this review side by side with the M23. There are clear improvements in the design of the M23, but not to a great extent, and not in terms of power (C298 measures a hair higher at the knee in each case, actually).

@amirm I don’t suppose there’s still a chance to get the reactive load test on the C298 that you did for the M23 but which doesn’t appear here?

This was a long time coming. Thanks for testing, and to whomever sent it in!

 

[NTK]

Did NAD in the past had this level of performance before purifi modules ? If yes which amps were those ?

The NAD 2200 power amp from 35 years ago would be audibly indistinguishable, and can provide even a little bit more burst power (which is what counts for music reproduction) into 4 ohms.

 

[Deleted member 48726]

The NAD 2200 power amp from 35 years ago would be audibly indistinguishable, and can provide even a little bit more burst power (which is what counts for music reproduction) into 4 ohms.

And can be had for about 200 USD regularly where I live. Of course some of them may need some TLC.

 

[Jimmyblues1959]

This is a review and detailed measurements of NAD C298 stereo class D power amplifier based on Purifi Eigentakt modules. It is on kind loan from a member and costs US $2,399.
View attachment 308806
The unit is quite heavy for a class D amplifier. The front is plain as most power amps are. I was not a fan of the status LED. On power up, it turns orange. If you hit the power button, it initially goes red making you think there is a fault. But eventually switches to blue saying it is on. Back panel shows some nice features such as fixed and variable gain and selectable level for trigger input (auto power on):
View attachment 308807
I realize NAD reserves their exquisite casing for their "Master" series but if I am paying $2,400 for an amplifier, I expect something better than stamped sheet metal cover and utilitarian binding posts. FYI the vents on top are only on top of one amp heatsink and not the other. Seemingly they went for looks rather than usefulness there.

NAD C298 Amplifier Measurements
I started measuring with fixed gain and was pleased to see the gain close to our nominal 29 dB:
View attachment 308810
Distortion is vanishingly low at -120 dB and it is noise that brings it down to a very respectable 100 dB SINAD:
View attachment 308811

View attachment 308812

I was hoping to get even better performance by lowering the gain to 15 dB. That did not happen:
View attachment 308813

We actually have more distortion and some mains noise as well! So back to fixed gain for the rest of the tests. Here is RCA input:
View attachment 308814

Dynamic range is excellent:
View attachment 308815

View attachment 308816

Multitone distorting is very low but with some increase at higher frequencies:
View attachment 308817

Which is reflected in dual 19 and 20 kHz tones:
View attachment 308818

Frequency response is flat and load independent which is great:
View attachment 308819

Crosstalk is excellent:
View attachment 308820

Let's see how much power we have:
View attachment 308821
That's quite healthy and gets even better if we allow 1% THD:
View attachment 308822

No, I didn't test the bridge mode. Stereophile did and it does pump out a ton of power.

Here is the 8 ohm power:
View attachment 308823

Sweeping with different frequencies shows unhappiness only when frequencies go above 5 kHz:
View attachment 308824

Power on is silent although there is a pattern in the idle noise which should have been caught and eliminated:
View attachment 308825
My target here is 1 mv and it is exceeded when unit is powered off so that may cause a pop.

The amplifier is stable on power up but has the same strange variable pattern:
View attachment 308826

Conclusions
If you want an amplifier with state of the art class D module in it, your choices are usually from smaller independent companies. NAD is one of the exceptions in major brands to offer an amplifier with Purifi module in it. That comes at a premium in retail cost due to channel and brand overhead. The C298 delivers excellent performance with just some minor issues in variable gain and idle noise.

I am going to put the NAD C298 on my recommended list. But if I were you, I would cut back on eating out for a couple of years and save money to get the beautiful master series.

Manufacturers Specifications:​

ANALOG AUDIO INPUT/LINE OUT​

• THD (20 Hz – 20 kHz)
• <0.0005 % at 2V out
• Signal-to-Noise Ratio
• >120 dB (IHF; 20 Hz – 20 kHz, ref. 2V out)
• Channel separation
• >110 dB (1 kHz)
  >100 dB (10 kHz)
• Input impedance (R and C)
• Single-ended: 56 kohms + 280 pF
  Balanced: 56 kohms +280 pF
• Maximum input signal
• >7.0 Vrms (ref. 0.1 % THD)
• Output impedance
• 390 ohms
• Frequency response
• ±0.1 dB (20 Hz – 20 kHz)
• Maximum voltage output -IHF load
• ≥>7.0 V (ref. 0.1 % THD)

ANALOG AUDIO INPUT/SPEAKER OUT​

• Rated output power into 8 Ohms and 4 ohms (Stereo mode, ref. 20 Hz-20 kHz at
  rated THD, both channels driven)
• 185 W at 8 ohms
  340 W at 4 ohms
• Rated output power into 8 Ohms
  (Bridge mode, ref. 20 Hz-20 kHz
  at rated THD, both channels driven)
• 620 W at 8 ohms
• THD (20 Hz – 20 kHz)
• <0.005 % (1 W to 185 W, 8 ohms and 4 ohms)
• Signal-to-Noise Ratio
• >98 dB (A-weighted, 500 mV input, ref. 1 W out in 8 ohms)
  >120 dB (A-weighted, ref. 185 W out in 8 ohms)
• Clipping power (Stereo mode, at 1 kHz 0.1 % THD)
• >200 W
• Clipping power (Bridge mode, at 1 kHz 0.1 % THD)
• >690 W
• IHF dynamic power (Stereo mode, at 1 kHz 1 % THD)
• 8 ohms: 260 W
  4 ohms: 490 W
  2 ohms: 570 W
• IHF dynamic power (Bridge mode, at 1 kHz 1 % THD)
• 8 ohms: 1000 W
  4 ohms: 1100 W
• Peak output current
• >25 A (in 1 ohm, 1 ms)
• Damping factor
• >800 (ref. 8 ohms 20 Hz – 6.5 kHz)
• Frequency response
• ±0.2 dB (20 Hz – 20 kHz)
  -3 dB at 60 kHz
• Channel separation
• >100 dB (1 kHz)
  >80 dB (10 kHz)
• Stereo Mode input sensitivity (for 185 W in 8 ohms)
• Fixed Gain mode: 1.43 V
• Stereo Mode Gain
• Fixed Gain mode: 28.6 dB
• Line In – Balanced and Single-ended
• Variable Gain mode: 8.5 dB – 28.5 dB
• Bridge Mode Sensitivity
• Fixed Gain mode: 3.78 V for 620 W in 8 ohms
• Line In – Balanced and Single-ended
• Variable Gain mode at maximum: 1.41 V for 620 W in 8 ohms
• Bridge Mode Gain
• Fixed Gain mode: 25.4 dB
• Line In – Balanced and Single-ended
• Variable Gain mode: 14.5 dB – 34.5 dB
• Standby power
• <0.5 W

DIMENSION AND WEIGHT​

• Gross dimensions (W x H x D)
• 435 x 120 x 390 mm (17 1/8 x 4 3/4 x 15 3/8 inches)
• Net weight
• 11.2 kg (24.7 lbs)
• Shipping weight
• 13.6 kg (30 lbs)

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As always, questions, comments, recommendations, etc. are welcome.

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Nice review Amir! I still have my 1980's NAD 3130 Integrated amplifier. It's a workhorse with a very pleasant
sound.

 

[pogo]

Have we figured out what NAD was trying to achieve with the custom mods? I’m curious what benefit they thought justified the slight deterioration in performance. Reliability? Speaker protection? The world wants to know.

Performance/Headroom, which depends on physical implementation and system-level circuitry/configuration (thermal system, power supply section, ...).
Not without reason, the dynamic power is 750W into 2 ohms. The bridge mode also makes the custom mods necessary.


This could also apply to the C658/C298 combo:
NAD has added a gain stage to increase its headroom so that it works better with the DSP circuits of its room-correction software and tone controls. NAD concedes that this slightly decreases the M33’s signal/noise ratio, but with careful design and premium parts, and because the Eigentakt’s S/N is so low to begin with, the noise is still inaudible.
Source: soundstagehifi.com