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Benchmark AHB2 / Class D Purifi Eigentakt / Mark Levinson 333 - Listening impression & Conclusion

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#1
I have these 3 amplifiers and am curious how they compare in my environment.

Equipment setup:

CD/SACD player: Oppo BD105
Stereophile’s Test CD2 , Track 15 pink noise, , for level matching the three amplifiers​
Volume set 72dBC on track 15 before playing songs B - F​
Volume set to 82dBC on track 15 before playing songs G-H​
Standard Music :​

  • B - SACD Norah Jones, Come away with me
  • C -SACD Andrea Bocelli, Melodramma
  • D -SACD Dire Straits, Walk of Life
  • E -SACD Pink Flyod, Time
  • F -CD Ultimate Demonstration Disc: Chesky Records’ Guide to Critical Listening, Track 3 Spanish Harlem
Life Classical Recording Music:​

  • G - SACD Telarc Tchaikovsky 1812 overture, Track 7 Cossack Dance from Mazeppa
  • H -SACD Telarc , Donald Runnicles , ORFF Carmina Burana , track 10 were diu werlt alle min
Blu-Ray Movies:​

  • I -John Williams Live in Vienna, Track 19 Imperial March , watching in 2ch mode
  • J -Patriot, Uncompressed LPCM Audio track, Scene 6
Apple TV 4k:
    1. Streaming Apple music (various pop songs Taylor Swift, Marron 5, etc)
    2. YouTube podcast (for center channel compare)
    3. HBO Max Movies (for center channel compare)

Pre-Pro Anthem AVM50v, XLR audio input from oppo.
802D3 Speakers (Front) , HTM1D3 (Center) , old DM640i (Surround back)
Amplifiers under test:
  1. Mark Levinson No 333
  2. Benchmark AHB2
  3. VTV Purifi Eigentakt EVAL-1


Listening Impression (Stereo 2ch mode):
  • For songs B-F , level match volume based on Track 15 pink noise (A1 above) , resulting in typical music volume swings around 80dB-86dB. They all sound good. The Benchmark and Levinson sounds very similar in tonal balance, my son (blind test) could not tell them apart. The Benchmark AHB2 sounds very clean on E) Time , the ring sounds the clearest. On v vocal on AHB2 sounds a little bit less weight (Andrea Bocelli voice sounds less vibrato) compare to others. Levinson sounds very similar to AHB2 but the vocal is is more full and the bass has more weight. The Class D Purifi Eigentakt tonal balance has stronger mid-bass/low midrange so the vocal sounds more forward and closer but the upper treble is rolled off. The sound of cymbals are not as clear and not as distinct compare to levinson 333 or benchmark. AHB2.
  • For songs G-I, volume knob has to increase by 10dB (A2 above) to compensate for the recording sound level. The Class D Purifi Eigentakt sounds compressed (lack impact), at loud level, the sounds of each instruments are not as delineated, and the high frequency triangle and cymbals are not very clear in comparison to benchmark AHB2 or levinson 333. Both levinson 333 and benchmark AHB2 sounds very similar, but when the dynamic sound peak at 94dB, the 333 sounds more at ease and each individual instruments details are more distinct (more details of cello vibration and triangle resonance) than the AHB2.
  • It is hard to tell apart AHB2 vs 333 but easy to identify the Class D Purifi once we have heard all three on the same or specific songs. The Class D Purifi has rolled off treble and forward midrange that is its strong signature (by comparison, it sounds neutral/normal on its own when there is nothing to compare). This roll off treble reminds me on my previous Krell KSA-200s sonic signature.
  • The life recording song G-H has very wide dynamic (55dB – 94dB swing). Since my son played at the orchestra, I know what orchestra sounds like sitting in front rows. In my observation, to reproduce this life-like sounds of life orchestra is probably the most demanding for high resolution speakers and amplifiers. When playing loud level , songs G-I , the old Levinson still sounds the best.
  • When playing loud dynamic music song G-I, we heard changes in Class D Purifi tonal balance, the peak sounds certain instruments are level off compare to AHB2 or 333. Could the Class D PWM sampling be manipulated so the peak musical waveform dynamic is lost to bias for more midrange clarity ? Or is there soft clip mode where certain peak music waveform is “clipped” so they sound “compressed” . I don’t know but what we heard is a more compressed dynamic relative to AHB2 or 333 on song G-I.

Listening impression (Movie, using it to drive center channel)
  • Playing with K-M, AHB2 (mono bridge mode) and 333 sounds the same.
  • Playing with K-M, even level matching with AVM50v built-in level calibration (per SPL meter), the dialogue still sounds louder with the Class D Purifi. It correlates with our stereo experience where purify midrange is more forward sounding but less treble.
  • This Class D Purifi amp is good match for center channel or a PA system, it accentuates midrange voice (in comparison, sounds "neutral"/normal when listening to it without any comparison). So the dialog is more clear (e.g. comparison on streaming podcast from apple TV).
  • Try watching the Blu-ray Patriot movie Scene 6; It has both uncompressed 5.1 PCM and standard Dolby Digital 5.1. The dialogue on Dolby Digital 5.1 is more clear due to compression (special effects, music, weapons sounds are compressed) . However, if one has dedicated room , speakers and amps, one would want to watch it in uncompressed PCM for more immersive and open sound.

My personal conclusion:
  1. Class D amplifiers have improved a lot of the years but Class D Amps are still no match to good design Class AB Amp.in term of sound quality and dynamic handling
  2. Benchmark AHB2 is more versatile (good for all music) and more dynamic than the Class D Purifi Eigentakt
  3. Class D Purifi Eigentakt is suitable for center channel, its slight compression and unnatural bias toward midrange makes dialogue more clear It is not an ideal amp for life classical music reproduction.
  4. Mark Levinson 333 is the best despite its old age. It is the most life-like, with more weight on vocal , and more at ease when playing life recording classical orchestra at higher volume level
  5. There needs to additional scientific measurements that can explain why the benchmark AHB2 sounds better than Purifi Eigentakt in my environment and why the levinson sounds more dynamic and detailed on loud classical music. Traditional SINAD, THD , IMD measurement using sinewave do not have the musical waverform complexity and can not explain the contrast of what we heard among these amplifiers in our environment. What we heard can not be explained with just THD measurement as they all sound good (not distorted) but different. As below certain THD, the delta is not audible.
 

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#2
Thanks for the nice write-up, as I am about to pull the trigger on a VTV. The results/ conclusions you have are based on the Anthem and your speakers. Is it possible one (or both) is shelved down in the treble? For me it's hard to draw conclusions when trying out a piece of equipment other than how it works with whatever else is in the chain, versus a generic 'this (amp, preamp, etc.) is better than that (amp, preamp, etc.)' that will apply to everyone in all systems.

In my limited experience with equipment over the last 40+ years the preamp and speakers have the most influence on the sound, as long as the amp is not pushed out of its comfort zone. Speakers are rarely (never?) neutral. What you hear (and like/ dislike) is not due to a single component but to several of them.

This is actually why I started following ASR a few weeks ago. I ultimately want everything to be as neutral as possible, and use processing to dial in 'more pleasing' voicing as needed for specific recordings, etc. Component matching is time consuming and expensive when you are trying to get components that work with the faults of one's speakers.
 

audio2design

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#3
How much of your listening was blind?

There is little reason for the Purifi to roll off the highs. Literally none with your speakers. The AHB2 on the other hand would a small bit. Not enough data out there on the ML to say either way.

Sound meters are poor for level matching. Just being in the room using it screws up the measurement. Assuming flat amplifiers, you level match typically at 1KHz with a volt meter. That ensures accurate more accurate matching in most cases. There are better spectrums for volume matching but you need a remote reading meter so you don't impact the measurement.

Pink noise is poor for level matching. It significantly emphasizes the bass which actually punishes the amp with the best bass performance by making it quieter in other frequencies (perhaps your perceived roll off).
 
OP
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Thread Starter #4
How much of your listening was blind?

There is little reason for the Purifi to roll off the highs. Literally none with your speakers. The AHB2 on the other hand would a small bit. Not enough data out there on the ML to say either way.
Most of the test was blind. Especially when we want to confirm the differences on what we heard.
Agree. we can not explain the differences based on published measurement of frequency response with dummy load (not real speaker with varying impedance over frequency).

They all sound good and "neutral" on their own. I have them all for different setup.

I was sharing and emphasizing the contrast ; if you were here with us, and have listened to the same songs a few times, you would notice it for sure,.
The contrast that we heard needs a new metric of measurement to explain, it is beyond basic
The contrast is more obvious with life recording classical songs.
 
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OP
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Thread Starter #5
Thanks for the nice write-up, as I am about to pull the trigger on a VTV. The results/ conclusions you have are based on the Anthem and your speakers. Is it possible one (or both) is shelved down in the treble? .
I don't know. The only thing I changed in the compare was the amp.
They all sound good and "neutral" on their own.
I think VTV Purifi is a fine amplifier , definitely a step up from receiver built-in amp.
I was increasing the contrast....AHB2 cost more and Mark Levinson 333 is a heavy amp and not suitable for all environment.
 

boXem | audio

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#6
How much of your listening was blind?

There is little reason for the Purifi to roll off the highs. Literally none with your speakers. The AHB2 on the other hand would a small bit. Not enough data out there on the ML to say either way.

Sound meters are poor for level matching. Just being in the room using it screws up the measurement. Assuming flat amplifiers, you level match typically at 1KHz with a volt meter. That ensures accurate more accurate matching in most cases. There are better spectrums for volume matching but you need a remote reading meter so you don't impact the measurement.

Pink noise is poor for level matching. It significantly emphasizes the bass which actually punishes the amp with the best bass performance by making it quieter in other frequencies (perhaps your perceived roll off).
Indeed. The ultra low output impedance from the Purifi modules make their bass level significantly higher compared to more classical amplifiers (I have seen 1.5 dB below 100 Hz).
Another solution than voltmeter for level matching is recording the peaks from a given song and level match at 1 kHz.

Another point to take into account is that some implementations of the 1ET400A have significant DC at the output, potentially causing the speakers to distort.
 

boXem | audio

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#7
Something not clear in your report is what were the levels from the OPPO for each tested amplifier. I had a report similar to yours from a customer and after some investigation it appeared that he was experimenting digital clipping. Using a higher gain setting and lower digital volume solved everything.
 

Matias

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#8
Interesting report.

I didn't know the Mark Levinson No.333 but I found its measurements below. 700W in 4 ohms it's quite a powerful amplifier.
https://www.stereophile.com/content/mark-levinson-no333-power-amplifier-measurements

Also, if I understand correctly, the AHB2 was run in mono mode, so the Purifi was the lowest powered of the 3? If so that would explain the lower dynamics, especially the infamous canons on 1812.

Looking at the power x THD+N graphs in 4 ohms of each amp, on the knee before shooting up, we have:
Mark Levinson No.333: 650 W
Benchmark AHB2 (mono): 500 W
Purifi EVAL-1: 250 W

Also Purifi has the lowest output impedance and lowest distortion (IMD) on the treble. This probably correlates with the perceived rolled off treble.
 
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Matias

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#10
we're talking past 100 dB SINAD here.
In 1 kHz, sure. I was talking about high frequency. Look at the 333 THD+N graph below from Stereophile. This distortion in the treble say 7 kHz rises in 2W in 4 ohms to -70 dB, let alone in some 10 to 50 W should be even higher.

1296ML-FIG3.jpg
 

abdo123

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#11
In 1 kHz, sure. I was talking about high frequency. Look at the 333 THD+N graph below from Stereophile. This distortion in the treble say 7 kHz rises in 2W in 4 ohms to -70 dB, let alone in some 10 to 50 W should be even higher.

View attachment 133114
a newly born baby would have ~90 dB SINAD of sensitivity between 10K and 20KHz, even at worst case scenario at 4 ohm it's 60 dB SINAD.

I'm 23 and i barely have 20-30 SINAD sensitivity below 16KHz above 10KHz, with test tones. everything above 16KHz is just inaudible.

not to mention that the Speaker's IMD and THD would probably surpass any thing produced by electronics anyway.

It's theoretically possible, but i seriously doubt this is the answer.
 

Matias

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#12
I agree that above 10 kHz is more difficult to hear, and usually people don't complain of more or less "air" up there. What usually people hear and find differences is more around 5 to 7 kHz, where sibilances are (S's and F's in the vocals). And the hearing threshold in this range is still quite sensitive.

Fletcher–Munson.jpg

Other than the amplifiers the rest of the system was the same, so it is not a variable, only the amps are causing the perceived differences.
 

abdo123

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#13
Other than the amplifiers the rest of the system was the same, so it is not a variable, only the amps are causing the perceived differences.
I don't think you understood what i meant, lets assume that the speakers have a IMD and THD of 1% at that particular volume (the majority of high end speakers are tweeter limited so that's not a very shoddy estimate).

the addition of a -60 dB signal would mean absolutely nothing.

1622546613258.png
 

Matias

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#14
I understand that. In theory speakers have so much more distortion that all electronics should sound the same and be buried under the speaker's distortion. But somehow this does not happen, as we can see from this report, still the differences in amps are perceivable.
 

Matias

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#16
Agreed! It is only a theory. I am open for ideas that correlate the measurements we have and what was reported.
 

Gorganzola

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#17
Congrats to @MasterApex for undertaking and documenting his amp comparison effort, (which I offered without necessarily agreeing with his conclusions).

To address the blind listening issue, apparently it was all sighted listening. Personally I believe that some people can hear differences some of the time depending on the specific amps being directly compared, (assuming the same system, same volume, etc). FINE: this isn't a belief confirmed by science.

I have personally compared my Pass Labs X150.5 with my VTV Purifi stereo amp in my system. They have comparably power and I listen at relatively low volume, average about 68 dB, albeit mainly with highly dynamic Classical music. My conclusion is that the Pass amp is smoother and more forgiving of poor recordings but that the Purifi is ultimately more dynamic, transparent, and has much crisper dynamics as well as very solid bass. I sold the Pass and kept the Purifi.

Bottom line I don't agree that the Purifi "emphasizes the mid-range" nor that it isn't ideal for Classical music. But as I mentioned, the Purifi is less forgiving of not-so-great recordings; on the better recordings, it is superb for Classical or any music.
 
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Gorganzola

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#18
you have zero conclusive proof that this the actual reason though.
"Proof"? No, I hope MasterApex will agree that he isn't offering proof, only his impressions. Accordingly you can take them or leave them.

I have offered some impressions already, above, regarding the Purifi and an amp more like the Mark Levinson. Take 'em or leave 'em.:p FWIW, my conclusions are a bit different than the OP's based mainly on personal preference.
 
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Tokyo_John

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#19
This would be a good opportunity for some in-room high quality recordings at the listening position in order to show some objective data. The relative differences between the amps should be resolvable by a high quality recorder/mic that has more sensitivity than human hearing.
 
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Thread Starter #20
I have personally compared my Pass Labs X150.5 with my VTV Purifi stereo amp in my system. They have comparably power and I listen at relatively low volume, average about 68 dB, albeit mainly with highly dynamic Classical music. .
Thanks for sharing.
Curious if you could try playing or streaming SACD Telarc Tchaikovsky 1812 overture and share your experience?
Level match or crank them louder so the contrast is more audible.
 
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