Comparing the NAD C298 and 1ET6525SA Purifi-based Buckeye build

[rjp]

What do mainstream amps such as NAD C298 offer that is different than what we can get with independent amp builders such as Buckeye?

To my understanding, they both use the Purify Eigentakt 1ET6525SA modules, though based on photos of the inside the NAD clearly has a lot more "stuff" in it. I realize the input boards are different in each, and the power supplies are different.

I assume they will sound pretty much identical in normal operation, but what, if anything, is in the NAD that makes it worth more than twice the price?

I am curious about the stuff that gets overlooked, like any differences in supporting circuitry such as the input stage, power supply capability, and how over-voltage protection is implemented.

I noticed NAD specs their amp as 185 watt into 8 ohms whereas Buckeye specs 230 watts. I do measure very close to 230 watts rms from the Buckeye into 8 ohms before distortion. Since they are the same power amp modules I am assuming the difference is related to how they are driven. The Buckeye seems to have zero headroom above the specified input level (2.3 vrms on high gain) which I understand is fairly typical for class D implementations. I noticed that if this level is exceeded, even slightly, jagged clipping at the sinusoid peaks begins immediately, followed by automatic shut down. Although the amp has a clipping indicator LED on the front panel, there seems to be no stage where clipping is indicated but shutdown does not yet happen. At least not that I have encountered. I am wondering if maybe NAD backed off on the gain a little bit to provide some headroom, or if they have developed a more sophisticated over-voltage protection circuit that is able to compress the peaks or limit them in a smoother, flatter manner rather than the jagged high frequency oscillations I observe on the Buckeye.

EDIT: I should point out that while this peak distortion looks bad on the scope, the amp sounds great. For all I know, this may just be the normal way class D limits itself. I would like to learn more about how this works, and would appreciate very much if someone could provide a link to better understand this technology.

Other than (potential) little details like this, I can't think of any good reason to spend more money for the top-tier name brands.

Are there other differences? It would be great to hear from anyone who has personally tried both.

 

[johnsen88]

The one thing I feel NAD does often is to spec their products modestly. I believe this one was pushed to its max and showed numbers slightly above what they published. I will be interested to know what the other esteemed members here have to say because I own one myself after Amir's assessment and later published measurements.

 

[rjp]

I’m struggling to understand how class D handles short peaks as in IHF peak power ratings, and if it is any different than class AB designs. It seems like there may be a single absolute output voltage achievable that may limit both the rms and brief (4% duty cycle) peaks. Still reading.

 

[jdbob]

I noticed NAD specs their amp as 185 watt into 8 ohms whereas Buckeye specs 230 watts.

It all depends on the distortion level the manufacturer uses, the 230 watts according to the 1ET6525SA datasheet is at 1%. NAD might be using 0.1%. In Amir's review of the 3 channel Buckeye using the same modules he uses the "knee" where the distortion starts to rise significantly, in this case 172 W for 8 ohms and 265 W for 4 ohms.

 

[rjp]

It all depends on the distortion level the manufacturer uses, the 230 watts according to the 1ET6525SA datasheet is at 1%. NAD might be using 0.1%. In Amir's review of the 3 channel Buckeye using the same modules he uses the "knee" where the distortion starts to rise significantly, in this case 172 W for 8 ohms and 265 W for 4 ohms.

I think the 3 Chan Amir reviewed was the first generation purifi. I assumed that was why it had lower power.

Buckeye 3 Channel Purifi Amplifier Review (2nd)

This is a second review of the Buckeye 3-Channel Purifi based balanced class D amplifier. First sample had an issue with its binding posts increasing distortion. It costs US US $1,595. Typical of Buckeye amplifiers, focus on what is inside rather the case which is utilitarian. An indicator...

www.audiosciencereview.com

 

[jdbob]

I think the 3 Chan Amir reviewed was the first generation purifi. I assumed that was why it had lower power.

Buckeye 3 Channel Purifi Amplifier Review (2nd)

This is a second review of the Buckeye 3-Channel Purifi based balanced class D amplifier. First sample had an issue with its binding posts increasing distortion. It costs US US $1,595. Typical of Buckeye amplifiers, focus on what is inside rather the case which is utilitarian. An indicator...

www.audiosciencereview.com

I don't see any evidence that there was a 1st generation 1ET6525SA board. Looking at the data sheet the 8 ohm knee looks like what Amir has, but the 4 ohm knee is over 300 watts, I don't know what to think. Maybe I should just stop trying.

 

[rjp]

I meant first gen Eigentakt module. I think it was 1ET400A. The second gen eigentakt (1ET6525SA) was released in late 2024, Since Amir’s review was in 2023 I figured it was first gen.

 

[jdbob]

I meant first gen Eigentakt module. I think it was 1ET400A. The second gen eigentakt (1ET6525SA) was released in late 2024, Since Amir’s review was in 2023 I figured it was first gen.

Makes sense now. That review never actually says what the module is and I incorrectly assumed it was the 1ET6525SA. The only thing left of my post that doesn't suck is the point that the manufacturers can pick whatever distortion value they want to advertise the power. They could even get really cheeky and use 0.069%

 

[Oniiz86]

To my understanding, they both use the Purify Eigentakt 1ET6525SA modules

@rjp I know you know this but you should correct the first post as the NAD C298 was released prior to the release of the 2nd Gen Purifi 1ET6525SA module in late 2024 & definitely utilises Purifi's 1st Gen 1ET400A module.

 

[Redacted]

The main things are paying for a badge and your preferred case.
You could argue that the big brands offer service and support, and many would say relibility, but that has been the opposite of my experience over the years. If I lived in the US, I'd be far more likely buy a Buckeye than a NAD, but then I am always looking to save money....

 

[-Matt-]

There are claims in the Nad C298 review thread that Nad use custom modules rather than directly using the Purifi 1ET400A modules...

https://www.audiosciencereview.com/...98-stereo-amplifier-review.47531/post-2109548

I recall that this was certainly the case for the Nad M27 which used a modified version of the Hypex NC400 module.

Original Hypex NC400 modules are round:

Whilst Nad NC400 OEM is rectangluar:

 

[Redacted]

I dunno about Purifi, but Hypex certainly offer slightly customized versions of their boards _ Cambridge Audio being an example.
The cynic in me says it is to prevent users swapping out otherwise identical modules for repairs or upgrades, plus being able to market "special sauce" - it's what I'd do a as big brand../..

 

[rjp]

@rjp I know you know this but you should correct the first post as the NAD C298 was released prior to the release of the 2nd Gen Purifi 1ET6525SA module in late 2024 & definitely utilises Purifi's 1st Gen 1ET400A module.

I did not know that! Thank you for pointing this out.

I just did a search and, yes, the C298 uses first gen Purifi. The NAD Masters M23 V2 is the one using the second gen Purifi. I will try to correct the title and my first post.

• NAD Masters M33 / M33 V2 (integrated streaming DAC/amplifier) — HybridDigital Purifi Eigentakt; 200W/ch into 8/4 Ω. The V2 uses the latest-generation Purifi Eigentakt modules plus updated ESS DAC.
• NAD Masters M23 / M23 V2 (stereo power amplifier) — Purifi Eigentakt; 200W/ch (8 Ω), 380W/ch (4 Ω); bridgeable to ~700W. V2 features second-generation Purifi Eigentakt modules.
• NAD Masters M28 (7-channel power amplifier) — Purifi Eigentakt; 200W/ch into 8 Ω (all channels driven). Shares similar amp boards with the C 298 in some implementations.
• NAD C 298 (stereo power amplifier) — Purifi Eigentakt; 185W/ch into 8 Ω, 340W/ch into 4 Ω; bridgeable to 620W.

 

[rjp]

It seems there is no way to edit my first post or the title to correct my mistake now.
I should have said NAD Masters M23 V2 instead of NAD C298.

So now the price difference is even greater (4x)

What does the NAD Masters M23 V2 offer that is better than the Buckeye using the same second gen Purifi Eigentakt technology?

 

[Kal Rubinson]

There are claims in the Nad C298 review thread that Nad use custom modules rather than directly using the Purifi 1ET400A modules...

NAD has often stated that they manufacture these boards under license but how "custom" they are remains undefined.

 

[-Matt-]

I know you know this but you should correct the first post as the NAD C298 was released prior to the release of the 2nd Gen Purifi 1ET6525SA module in late 2024 & definitely utilises Purifi's 1st Gen 1ET400A module.

I did not know that! Thank you for pointing this out.

I should have said NAD Masters M23 V2 instead of NAD C298.

So now the price difference is even greater (4x)

Another distinction that you should be aware of is that the C298 is part of Nad's Classic line, whilst the M23 is part of the Masters line.

The Masters line are Nad's premium range, whilst the Classic line is intentionally more basic/standard. (The case will be a lot more substantial for the Masters range).

This makes it even less reasonable to make a direct cost comparison with a no-frills option such as Buckeye.

 

[Redacted]

"Nad's Classic line, whilst the M23 is part of the Masters line"

Jeez, we're into marketing positioning again....

 

[rjp]

Is it known if the NAD M23 v2 has any performance/sound quality differences compared to the Buckeye?

 

[-Matt-]

Probably not so much difference in sound quality or audio/electronic performance (refer to @amirm 's reviews for measurements). Possibly Nad may score slightly lower on absolute values due to more conservative power supply design.

More meaningful differences would be in feature set (for example the Nad might include protection circuits and nicer casework not present on a more basic offering). If such things mean nothing to you, then there perhaps isn't much benefit in getting the Nad.

"Nad's Classic line, whilst the M23 is part of the Masters line"

Jeez, we're into marketing positioning again....

Masters vs Classic vs Buckeye would have an impact on potential resale value which should be factored into total cost of ownership.

 

[rjp]

Has Amir reviewed any Buckeye amps using the Purify 1ET6525SA modules?
I searched but could not find.