NAD C 298 Power Amplifier With Purifi Eigentakt Amplification

[Kal Rubinson]

Anyone know if this amp is rack mountable. Seems it should be but there is no mention of it on NADs site that I can find.

The present chassis does not seem to be suitable in design for that.

 

[mSpot]

Anyone know if this amp is rack mountable. Seems it should be but there is no mention of it on NADs site that I can find.

I would say no. NAD is consumer, not pro oriented and I see only a single product across their entire range that has a rackmount option (a modular amp for custom home installations).

 

[crbdrb]

I would say no. NAD is consumer, not pro oriented and I see only a single product across their entire range that has a rackmount option (a modular amp for custom home installations).

I have asked my dealer, but I am sure you are correct.

 

[crbdrb]

The present chassis does not seem to be suitable in design for that.

I just saw the photos of the internal chassis. You are absolutely correct.

 

[crbdrb]

What does the 80 W mean in this context from the spec sheet?

Rated output power into 8 Ohms and
4 ohms(Stereo mode) 80 W (ref. 20 Hz-20 kHz
at rated THD, both channels driven)

 

[Kal Rubinson]

What does the 80 W mean in this context from the spec sheet?

Rated output power into 8 Ohms and
4 ohms(Stereo mode) 80 W (ref. 20 Hz-20 kHz
at rated THD, both channels driven)

Typo?

 

[ebslo]

What does the 80 W mean in this context from the spec sheet

Rated output power into 8 Ohms and
4 ohms(Stereo mode) 80 W (ref. 20 Hz-20 kHz
at rated THD, both channels driven)

Look at the NAD C 268 datasheet. The exact same verbage is there but formatted such that "80 W" is the specification instead of a qualifier for the actual value. It's a copy-paste error from that datasheet and is nonsensical in the context of the C 298 datasheet.

Edit: although that does raise the question of exactly how much of it is copy-paste error. Is the "(ref. 20 Hz-20 kHz at rated THD, both channels driven)" part copy-paste error too? I hope not, but who can say?

Edit 2: Post #332 below clears up the above potential for confusion, the specification in question is properly stated in the owners manual.

 

[Moto]

Different question on the C298 here. There are a hundred threads about amplifier power, input sensitivity, etc. but I can’t seem to synthesize a good answer to my issue from them. I hope for some help from all of you.
I bought a C298 to use with some ATC SCM40’s(85db) and an SMSL SU9 dac. According to the measurements here, that puts out 5.3vrms at max/fixed volume and that’s the way I run it directly into the C298 using balanced inputs.
I only listen to Qobuz through roon and control volume using the 64bit dsp volume control there.
So the question is, what do I set the variable gain control on the C298 vs the roon volume control? The variable gain goes from 8.5-28.5db on the C298.

 

[Moto]

Sorry accidentally posted without finishing. Fixed gain(28.5db) input is 1.43v for the rated 185w. I assume running it at the lowest gain possible(8.5db) is the best noise scenario. At 0 db in roon and using the minimum 8.5db gain, this gives me 75-80db at my listening position according to REW and a calibrated mic. And I don’t listen louder than this. what effect is the 5.3vrms output of the SU9 having relative to the 1.43vrms sensitivity of the amp at 28.5db fixed gain? This fixed gain is 20db or 10x higher than the minimum gain I am using. Does that therefore mean that the sensitivity of the C298 is 10 x 1.43=14.3vrms for the rated 185w if using that minimum gain setting? If so then the SU9 can never drive the amp to 185w.
I’m very confused on this and hope you can straighten things out for me. Thx much

 

[ebslo]

I’m very confused on this and hope you can straighten things out for me.

If your preamp can put out 5.3V RMS and you want to be able to drive the full 185W into 8Ohms then the power amp needs 20 * log10(sqrt(185W * 8Ohms) / 5.3V) = 17.2dB gain.

 

[Moto]

Ok that makes sense. So the fact that I only need to set the variable gain of the C298 at its lowest, 8.5db, means I don’t need 185w for my listening level, room, etc.
1. Am I better off distortion wise leaving the amp gain setting at 8.5db or turning amp gain up and then turning my roon dsp volume down?
2. The following is from the NAD spec sheet

• Maximum input signal
• >7.0 Vrms (ref. 0.1 % THD)
  
  I don’t know how to interpret that regarding clipping etc. Any ideas?
  
  There isn’t a clipping spec there. How do I determine what it is and if I wanted to give myself say 20db of headroom before clipping, what the output level from my SMSL dac should be?

 

[Kal Rubinson]

Look at the NAD C 268 datasheet. The exact same verbage is there but formatted such that "80 W" is the specification instead of a qualifier for the actual value. It's a copy-paste error from that datasheet and is nonsensical in the context of the C 298 datasheet.

That insertion "80 W" does not appear on the specs in the Owner's Manual.

 

[Jukebox]

So finally we have a good set of measurements

https://www.soundstagenetwork.com/i...ts&catid=97:amplifier-measurements&Itemid=154

 

[KarVi71]

Measurements look very good.

And they are from the future it seems

 

[Matias]

So finally we have a good set of measurements

https://www.soundstagenetwork.com/i...ts&catid=97:amplifier-measurements&Itemid=154

Thanks, added to the listing. That is THD+N at 0.009% SINAD 81 at 5W 4 ohms.

 

[Joaquinín]

Thanks, added to the listing. That is THD+N at 0.009% SINAD 81 at 5W 4 ohms.

SINAD 81 at 5W 4ohms is state of the art amplification? Am I misinterpreting something?
What´s the difference between this SINAD measurement and the ones from Amir? May be Amir´s is measured with a 1 Khz input and this one is at the amps most distorted frequency (15+ khz?)? Shouldnt the "Amplifier SINAD listing" use a comparable measurement?

 

[Matias]

SINAD 81 at 5W 4ohms is state of the art amplification? Am I misinterpreting something?
What´s the difference between this SINAD measurement and the ones from Amir? May be Amir´s is measured with a 1 Khz input and this one is at the amps most distorted frequency (15+ khz?)? Shouldnt the "Amplifier SINAD listing" use a comparable measurement?

The ranking that Amir compiles used SINAD of 1 kHz at 5W into 4 ohms. I read these values (THD+N at 0.009% SINAD 81) in SoundStage! measurements.

This is not so great, as we can see from the list I compile below. This means that the amplifier modules are higher performing than the buffers used by NAD's implementation.

https://docs.google.com/spreadsheets/d/1ZlTOYxmPs938gqHjtDABkWS-MApu7uJjzIGnJ2Elm6Y/edit?usp=sharing

 

[ebslo]

Thanks, added to the listing. That is THD+N at 0.009% SINAD 81 at 5W 4 ohms.

This doesn't add up. I read the graph the same as you, but where does it come from? Both the distortion and noise are much lower, so how is noise + distortion this high. The FFT just below the THD+N graph gives a clue; it goes to 100kHz with noise rising sharply above 20kHz. I think the high THD+N is due to out-of-band noise above 20kHz, and they didn't limit the bandwidth for that graph. Looks to me like a Class-D amp's noise shaper doing it's job.

 

[ebslo]

So finally we have a good set of measurements

https://www.soundstagenetwork.com/i...ts&catid=97:amplifier-measurements&Itemid=154

Awesome, bang on the specification. I won't make comparisons with the Purifi reference design, but highly spec'd kit meeting it's spec this dead on makes me very happy.

 

[Matias]

This doesn't add up. I read the graph the same as you, but where does it come from? Both the distortion and noise are much lower, so how is noise + distortion this high. The FFT just below the THD+N graph gives a clue; it goes to 100kHz with noise rising sharply above 20kHz. I think the high THD+N is due to out-of-band noise above 20kHz, and they didn't limit the bandwidth for that graph. Looks to me like a Class-D amp's noise shaper doing it's job.

You are right: SoundStage! uses 90 kHz bandwidth, while ASR uses 22 kHz.
@pozz I think we have another problem....