Meier-Audio Corda Soul - Reviews
Pros: Transparent SOTA sound quality
Useful DSP features
Cons: Expensive
Some functional limitations
I’ve used an Oppo HA-1 as my DAC, preamp and headphone amp for 4 years. I love its clean neutral sound, driving HD-580 and LCD-2 Headhpones, and my Magnepan 3.6/R speakers. Yet I wonder whether better sound could be had.

Jan Meier built 2 Soul prototypes, each of which resembles a science project but is solid, if not elegant, and electrically and sonically equivalent to the production unit. If you contact him you can arrange to borrow the prototype. Jan has a generous policy of not charging to borrow it (though you have to ship it back to him in Germany), and he has a 14-day return policy for the final product.

It may seem unfair to compare the Oppo with the Soul, as the Soul costs several times as much. But the Oppo is what I have, and I’ve always believed, based on comparison with other headphone amps and DACs, that it punches well above its weight class.

From a distance, the Soul & Oppo sound similar, which is expected for DACs that are well engineered with excellent measurements. Both are neutral and transparent. However, the degree of similarity surprised me. I had to listen carefully to specific recordings that I know well, to hear reliable differences. Even then, the differences were subtle--but real, as I confirmed with blind tests. The differences were easier for me to hear on speakers. I suspect this is because my speakers are more neutral and resolving than my headphones. Audeze LCD-2 are great headphones but not as resolving as Magnepan 3.6/R. Most people, especially those with revealing headphones that are harder to drive (like the HD-800), will hear differences more easily on headphones than on speakers.

To characterize the subjective differences is to overstate them. But to summarize:
  • Bass: the Oppo has deep, clean bass yet the Soul in comparison makes the Oppo sound just a touch wooly. With excellent recordings of bass drums and violins, the Soul reveals more of the percussive attack/decay and complex timbre.
  • Midrange: the Oppo is neutral and clear, yet the Soul in comparison makes the Oppo sound just a touch veiled. Excellent recordings of piano and acoustic instrument ensembles take on greater clarity and slightly more pure voicing.
  • Treble: the Oppo is extended and linear, yet the Soul is just a bit smoother and more natural, making the Oppo in comparison sound like it has a hint of grain.
I'm not a big fan of DSP, which is too often used as a gimmick. But I have come to use the Soul's DSP features under certain conditions.
  • Tone controls: anyone with a big enough music library inevitably has poor quality recordings. The problem is often unbalanced frequency response, in which case the Soul's tone controls can improve things. Implemented in DSP, I find them more transparent than conventional analog tone controls.
  • Headphone crossfeed: the Soul has Meier's crossfeed, which narrows L-R separation and is useful when listening on headphones to recordings having artificial hard L-R separation. It has 5 levels from subtle to obvious.
  • Speaker crossfeed: the Soul has a separate function to widen L-R separation for speakers, with adjustable levels to tune for different speaker distances & angles.
  • Headphone notch filter: many headphones have a narrow response peak. The Soul has an adjustable notch filter to tame these headphones. The filter is always -6 dB, Q=2, and the knob adjusts the frequency between 6 and 11 kHz. This is particularly effective with the HD-800.
  • Digital filter: the Soul has a switch to select the standard "sharp" (linear phase) versus "slow" (minimum phase) digital filter.
  • Redbook emphasis: the Soul implements this and provides a manual override. This is more of a historical curiosity since this obscure feature of the CD Redbook was so rarely used. But if you have old CDs from the 80s or 90s that used it, it's nice to have.
The Soul has excellent build quality, among the top tier in consumer & professional audio. It also has excellent support from Jan Meier, who stands behind his products and is willing to customize some aspects to suit individuals.

The Soul has some unusual engineering features that contribute to its excellent sound quality:
  • Volume control is a 64-step switched attenuator in the analog gain-feedback loop. When you turn down the volume it reduces the gain rather than attenuating a fixed gain ratio. This reduces noise and distortion, especially at the low to medium volumes we actually use when listening.
  • Switched power supplies - providing dead flat quiet stable DC to all internal components (digital and analog) without even a hint of 50/60 Hz ripple.
  • Frequency shaped feedback (FF), which "unloads" both digital and analog gain stages for cleaner more transparent sound.
  • The Soul uses dual DAC chips (Wolfson WM8741), one per channel (L and R), each in mono mode, in which this chip has slightly better performance.
The net effect of these engineering features makes the Soul the quietest (lowest noise) DAC or preamp I have heard or measured, especially at the low to medium volumes we actually use for listening. That lower noise contributes to absolute black musical background at all volume levels, accentuating low level subtle detail and transparency.

Now the Soul has some limitations:
  • Balanced only: no unbalanced inputs or outputs.
  • PCM only: no DSD. And sampling rates are limited to 32, 44, 48, 88.2, 96 and 192 kHz. No 176.4 or frequencies above 192k.
  • Analog output is max 8 Vrms for a full scale 0 dB digital signal. It has a gain switch, but it's digital so using high gain (+6 dB) risks digital clipping. It would be nice to have an analog high/low gain switch like Meier has in his other amps. This could match the output to a wider range of headphones, or to boost analog gain if you have DSP in front of the Soul attenuating the digital signal (for example, digital parametric EQ).
  • Appearance: the Soul looks and feels something like military signal processing equipment. Its build and part quality is impeccable, but no fancy displays, swanky enclosures or knobs. I enjoy this "black box" look and feel, but others might not, especially at this price point.
The Soul is the most transparent DAC and preamp that I have heard. It gets me closer to the music, making listening sessions more engaging. As an engineer, I like the non-nonsense industrial build quality that says "tools, not toys". I don't think more transparent, higher fidelity is possible at any price. For sound quality alone I would give it 5 stars (6, if I could!). But to be a realist I have to take it down 1/2 star due some of its limitations, which mean it won't be for everyone, and at its high price the field is wide open with so many other options to explore.
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Pros: Endgame DSP, DAC and headphone amp in one box, pure musical transperency, makes you existing headphones better with a notch filter to kill the strongest resonance frequencies
Cons: You might need to re-cable some of your favorite headphones

Sometimes the name of a product reveals so much more. This is the case with the “Soul”.

I have known Jan Meier now for quite a while. If I am not completely wrong since 2004/2005, when I ended up organizing the first Netherlands Headphone Meet. Over the years I had the chance to try out many of his headphone amps and DACs and also owned and own a few of them. I have observed Jan from the distance designing his new products and often had the chance to listen to the prototypes. But I have to be honest, never have I seen him work so long and with so much passion on a project comparable to the “Soul”. The “Soul” was one where he really took his time to get every detail right.

But one step after the other. In all the inventions Jan Meier made over time, the “ff” or “frequency-adaptive-feedback” technology was for sure one of the biggest ones, at least for me. I know many are raving about his perfect Crossfeed implementation, and while I see that it has its use, I did not realy need it. But his “frequency-adaptive-feedback” techology brought so much more transparency into my music listening that I am very thankful. Such a genius technology.

So when the Daccord DAC and the Classic became available with “ff” I ordered both and was in audio heaven. Honestly, after optimizing some digital and audio cables, I thought, this is it. It can not get better than this and I even started selling of my other headphone amps from other companies.

One day Jan showed up (I live conveniently on his travel route back home to the Netherlands, so he sometimes stops by to say hi) and he had hard wired connected the DAC output of his Daccord with the amp section of the Classic. So while they where still two units he just avoided a lot of inbetween pathway and circuits. He left this strange looking Siamese Gemini with me for 2 nights while he was in the Netherlands and wow, this was again a huge difference in blackness. Voice and music just appeared in the darkness of the night. It gave me chills.
I couldn’t believe what a difference the “melting” of the two units already meant.

This also as consequence was his switch to balanced because the signal from the DAC was balanced and to keep it is in its purest form, it meant to also go balanced in the output. I had many discussions with Jan over the years about this topic, and for a long time he was clear that with his “active balanced ground driving” technology there was no immediate need to ask headphone enthusiasts to get their cans recabled. But when he decided to create the best DSP/DAC/AMP unit he could, he switched to balanced without looking back.

But this was still just the start of his journey. Over the months and months whenever we talked about the “Soul” I was surprised that there was so much more he was building into this endgame machine. I guess the use of a DSP and programming of a DSP was also something new for Jan. But it allowed Jan to take one step of his “ff”-techology to the digital realms. Anothe important milestone to more transparency.

Under the hood:


Jan presented one of the new features of the Soul to me one day with his latest prototype, which looked already quite similar to the current layout of the switches etc. We all know that our headphones have a certain resonance frequency or spectrum, which some find very troublesome and others do not care so much about. Extremly famous is the Sennheiser HD 800 6kHz peak which drove Tyll Hertsens - former innerfidelity - nuts. Many mods were created by the community and finally Sennheiser created a 2.0 model - the HD 800s - which comes with Helmhotz resonator included.
Would we have had Jan’s Soul a bit earlier, this might have not been necessary. The built in 6 dB notch filter of the Soul allows you to dampen very effectively a very small frquency region without otherwise changing the sound.

Only when you are freed of a resonance you can value how much better the overall quality of the sound becomes. I have to be honest, I am no Tyll, I wouldn’t have figured out why the HD 800 was a headphone I found great but used very seldom at home, although it one of my most comfortable headphones. But suddenly with the peak gone, you have much more relaxed sound. Using the innerfidelity measurements one can do this too for other headphones and yes, the result is pretty astonishing.

Thanks to Jan I could test the Soul prototype also in his latest stages for over a week with different sources to drive the Soul. While the computer worked phantastic, my tries with iPad pro etc. via the apple camera adapter where not that promising. Seems that the Apple products doe not output bit perfect. Make sure you use the Soul with a device offering he digital signal unchanged. Quite important.

In the meantime I received my Soul which will stay with me.

With so much cleaness in the sound coming from the ff-techololgy being digital first, the notch-filter, the complete balanced design and so much more, you have to readjust your listening. Music does not sound like it sounded before. And the brain takes a while to re-adjust but this goes quickly and then the joy of having found a new level of listening will stay for a long time.

This DAC/equalizer/headphone amp offers clarity and precision in a never before heard quality. The acoustic room of the recording opens far and wide and you can kind of see the musicians playing.

Update March 2019: I asked Jan to re-cable two more of my headphones to XLR so I can use them with the Soul. Namely the Fostex Massdrop TH-X00 Ebony and the mitchell & johnson MJ2. I have to be honest, I was shocked how reveailing the Soul is when it comes to the audioquality of the headphones. I had used the mitchell & johnson MJ2 mainly with my pseudo-balanced Sony NW-ZX2 player and liked them so far. With the Soul you realy start to hear the original sound signature of the different headphones. Unfortunately without the gold glow of the Sony NW-ZX2 the mitchell & johnson sound quite trashy. So the extra cable will be unfortunately seldomly used.
The Fostex massdrop TH-X00 ebony sounds amazing, even if the fun tuning shows. After using the notch filter in the 10,4 kHz (-1 from the right side) the sound has improved strongly. Usualy the Fostex TH-X00 should have his hump at 11 kHz, but with my more comfortable, deeper Dekoni pads, there is more room and I guess by that the resonance frequency went a bit down.
I also used the 2nd tone control to decrease frequencies below 500 Hz. This makes the Fostex Massdrop TH-X00 a much more neutral headphone.
I am totally impressed how strongly the Soul can help to make a decent headphone to a great one.
Nice to see he's still making stuff! His site disappeared though, any ideas what's going on?
Richter Di
Richter Di
Having a blast with Qobuz streaming via SPDIF into the Soul. (A bit angry on Qobuz because I get pauses in some tracks, although I have the latest beta version from them for the FiiO M11)
Anyhow, Fostex massdrop TH-X00 ebony still my favorites. Had a fling with Nuraloops and Nuraphones, and while I have learnt something on the way, the Soul is just a true-full master. If you have the chance try it out.
I've been using the Soul daily for over a year now. It's proven reliable and sounds fantastic. Its transparency does full justice to the best modern high res recordings (especially classical music), and its crossfeed and tone controls have made some of my older and imperfectly recorded albums more enjoyable and musically engaging.

I occasionally listen to modern and electronic music which, sadly, are often poorly recorded with extreme dynamic compression. The Soul resolves these recordings quite well. I suspect it has something to do with the FF unloading the digital & analog stages, reducing the impact and distortion caused by recording flaws like intersample overs and clipping.