DAC, Preamp, Headphone Amp: Corda Soul and Oppo HA-1 (3 of 8)

This is part 3 of an 8 part series comparing the Meier Corda Soul and Oppo HA-1. Click here for the introduction.

Subjective Listening Notes

Before we dive into my notes, I must say that these are my personal subjective observations. I reliably detected these differences in level matched blind tests, so they are real. But I don’t claim they relate to advantages or flaws in any measurable engineering sense. I do my best to describe these differences as a neutral observer without judging which is “better” or “worse”.

For example, even terms like “pure” and “dirty” aren’t necessarily praise or criticism. “Pure” can be good, meaning free of distortion. Pure can be bad, meaning the reproduction of a natural sound is more pure than it sounds in reality (such as its complex timbre sounding filtered or simplified).

The Soul and Oppo are both high quality well engineered DACs with no obvious measurable flaws, they both have a neutral solid state sound without obvious euphonics or colorations. So the differences are necessarily subtle. We’re splitting hairs here, but that’s what high end audio is all about!

Also: I mention the recordings used but I only rarely give CD catalog numbers. You can probably find the exact recordings from the descriptions, but if you can’t, contact me and I’ll be happy to provide them.

Sun 12/23; speakers; direct, no EQ

  • Level testing
    • Set by ear using music and white noise without emphasis (equal energy all freqs 20 Hz – 20 kHz).
    • Tested with SPL meter @ listening position: subjective level matching was about ½ dB off.
    • Soul 12:00 Yellow (click 31 from minimum) = Oppo -14.5 to -15.0 dB (unbalanced line output).
    • Soul clicks measured as SPL, average 0.5 dB per click around the center position
      • From 10:00 to 3:00 position, clicks 19 through 51.
      • Different from manual, which says 0.8 dB per click.
      • Perhaps the manual averages all clicks, which gives bigger number because the first few clicks are bigger jumps.
  • Brahms Clarinet Trio; Ax, Ma, Stoltzman; Sony; track 1:
    • The Soul resolves the instruments so you can hear slightly better what each is doing even during dynamic crescendos.
    • The clarinet and piano are voiced ever so slightly differently through the Soul, just a touch more pure to my ears.
  • The Elfin Knight; Frederiksen; track 3:
    • The Soul resolves the flute & string instruments slightly better especially when they’re in the background with other instruments playing.
  • Soul’s bottom octave (< 30 Hz) sounds weaker.
    • It’s there if you turn it up, but sounds attenuated relative to the Oppo at the same overall volume level.
    • This is perception, not measurement. Both Soul & Oppo have ruler flat frequency response, so this perception is probably related to something else going on in the sound.
  • Taheke; McGee/Krutzen; track 13: the harp’s lowest 25 Hz tones subtly push the air in the room from the Oppo, yet are less noticeable from the Soul.
  • Roots and Sprouts; Abou-Khalil; track 2: the double-bass solo is more audible from the Oppo, and the Soul portrays it with slightly less depth, but more subtle timbre.
  • Barley Moon; Ayreheart; 96/24; track 4: when the drum enters about 50 seconds into the track, it sounds slightly deeper and more compelling from the Oppo.
    • Soul’s mid-upper bass is slightly emphasized relative to the Oppo.
    • Soul’s midrange is slightly more pure than the Oppo.
  • Dowland First Booke of Songes; Grace Davidson, David Miller; Hyperion 96/24; all tracks: at first the Soul and Oppo sound identical, but deeper listening reveals that Soul renders Davidson’s voice as ever so slightly more pure, with sibilants just a hint softer.
  • Soul’s extreme HF (> 10 kHz) is slightly less than the Oppo.
    • ?? initial impression, more listening to confirm
    • Is it possible that this relative attenuation (however slight) contributes to the observed midrange purity?

Mon 12/24; speakers; direct, no EQ

  • Soul’s extreme HF (> 10 kHz) is slightly less than the Oppo.
    • Confirmed. The Soul isn’t lacking these frequencies, but they sound very slightly attenuated compared to the Oppo. Which sounds “best” depends on the recording.
  • Tarab; Abou-Khalil; tracks 2-4: the top overtones of the instruments are slightly more evident with the Oppo. The difference in tonality is so subtle, it’s like the difference in live listening just a few feet further away.
  • Eeg & Fonnesbaek; tracks 1, 3, 6: this great recording has a bit of edge on Eeg’s voice. This is more apparent on the Oppo than the Soul. The Soul sounds slightly more natural, yet still with more “edge” than reality. Which is more true to the slightly edgy original master is unknown.
  • Vivaldi Concerto for violin, flutes, oboes, bassoons; RV577; McGegan, Philharmonia Baroque; tracks 7-9: this fine recording is on the airy side of reality. The Oppo slightly accentuates this airiness while the Soul slightly de-emphasizes it. Unknown which is more true to original master but the Soul gives a more natural presentation for this excessively airy recording.
  • Soul’s bottom octave (< 30 Hz) is weaker.
    • Eeg & Fonnesbaek; tracks 1, 3, 6: the bass on the Soul sounds a tad tighter, perhaps just a hint more speed, grip & control, yet not quite as much depth and richness as the Oppo.
    • Saint-Seans Symphony 3; Stern, Kansas City; tracks 4, 6: about 15 seconds into track 4 the organ hits a deep soft 20-30 Hz tone that pushes the air in the room. Both Soul & Oppo portray this, but the Oppo has a touch more depth and energy.
  • Soul’s midrange is ever so slightly more pure than the Oppo.
  • The Elfin Knight; Frederiksen; several tracks: the Soul has a touch more midrange purity. This could be related to its relatively attenuated HF, but the impression is that it is slightly more damped, as if the brief pauses of silence in the music are quieter.
    • Note: usually, a perceived attenuation of HF (however slight) relates to less clarity, not more. The Soul’s character is enigmatic.
  • After a few hours of the above, listener fatigue set in… resume later

Same Day, Hours later…

  • Measured FR to see if it shows any hint of my above observations–probably not, buy why not check?
    • Recorded warble tones from Stereophile test CD #2, analog line-level balanced XLR outputs of each device (Soul, Oppo) to Tascam recorder.
    • Frequency response matches within 0.1 dB from 20 Hz to 20 kHz (1/3 octave spacing) except at extremes
      • Matched levels at 1 kHz.
      • 20 Hz: Soul is +0.05dB relative to Oppo (-1.35 vs. -1.4 recorded on Tascam)
      • 20 kHz: Soul is -0.25dB relative to Oppo (-1.35 vs. -1.1 recorded on Tascam)
    • These differences should be inaudible
    • NOTE: these levels are relative to each other, not absolute (the Tascam doesn’t have perfectly flat response).
    • HD unmeasurable; both below -90 dB
  • As expected.
  • The above subjective listening impressions are subtle.
    • Subtle changes near the threshold of hearing can be perceived differently from what they actually are (slight difference in loudness perceived not as loudness but as sounding “fuller” etc.).
  • In light of this, how to explain the differences I’m hearing?
  • They’re not psychosomatic; I can differentiate them blind.
  • It sounds as if the Oppo has a slight touch of extra frequency content in the upper mids to treble, and a hint more low bass energy.
  • Sometimes it sounds like a touch of extra detail, other times it sounds like a touch of glare or grain; depending on the music.
  • Could it be a slight difference in frequency response? Could it be harmonic or intermodulation distortion?
  • Unlikely, the measurements are so similar.
  • But subjectively, that describes what it sounds like.

Next, subjective listening notes part 4 (day 3)