I posted it elsewhere as I did this experiment back in May 2021.
I agree with Paul’s observation on amplifier sound quality so I also want share my experience.
I owned these 3 amplifiers and am curious how they compare in the same room/equipment/speakers in my environment.
CD/SACD player: Oppo BD105
Stereophile’s Test CD2 , Track 15 pink noise, , for sound pressure level matching the three amplifiers during listening
Volume set to 72dBC on track 15 before playing songs B - F
Volume set to 82dBC on track 15 before playing songs G-H
Pop Songs :
- 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
Classical Recording Songs:
- 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 Disc contents used for comparison:
- 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:
- Streaming Apple music (various pop songs Taylor Swift, Marron 5, etc)
- YouTube podcast (for center channel compare)
- HBO Max Movies (for center channel compare)
Pre-Pro Anthem AVM50v, XLR audio input from oppo BD105 during SACD/CD playback.
B&W 802D3 Speakers (Front) , HTM1D3 (Center) , old DM640i (Surround back)
Amplifiers under test:
- Mark Levinson No 333
- Benchmark AHB2
- 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 song E) Time , the ring sounds the clearest. On vocal on AHB2 sounds a little bit less weight (Andrea Bocelli voice sounds less vibrato) compare to the rest. 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 life -like 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 amp to drive center channel)
- Playing with K-M, AHB2 (mono bridge mode) and 333 sounds the same.
- Playing with K-M, even when we level match (per SPL meter) using AVM50v built-in level calibration, 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). If we have not heard the other, it sounds “neutral”/normal when listening to it without any comparison. The dialog sounds more narrow band/focus (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:
- Class D amplifiers have improved a lot of the years but Class D Amps are still no match to good design (low feedback) Class AB Amp.in term of sound quality and dynamic handling
- Benchmark AHB2 is more versatile (good for all music) and more dynamic than the Class D Purifi Eigentakt
- 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.
- 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
- Just like food, one can measure calories, salt level, etc in analytical lab but the tasting experience has to be done. We have yet to develop new scientific metrics (beyond simple sinewave or square waveforms measurement 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.