The Meier Audio Corda Soul is a great many things in a single box. It is also at the top of the line of headphone-related components designed and sold by Meier Audio.

Meier Audio Corda Soul DSP DAC and Headphone Amp Review

Highlights

Meier Audio Corda Soul DSP DAC and Headphone Amp

  • Exceptionally transparent sound output quality.
  • Extremely versatile and can be used in several applications.
  • Can be used to customize the sound output of your system to better match room acoustics.
  • Can be used as an equalizer to improve the sound of digital sources.
  • Can be used as a preamplifier.
  • Can be used to feed a different outboard DAC.
  • Six digital inputs and one USB input mean you can use quite a few sources.
  • Can be configured for either headphones or speakers.

Meier Audio Corda Soul DSP DAC and Headphone Amp

Introduction

The Meier Audio Corda Soul is a single device that acts as a headphone amplifier, DAC, digital signal processor (DSP), and preamp. It is designed and built by Dr. Jan Meier in Germany and sold by Power Holdings, Inc. in the United States.

It provides tone controls, balance controls, and crossfeed and notch filters all within the digital domain. These are all implemented in the digital domain with 64-bit resolution. And its DAC section uses two converter chips in dual-mono mode. Also, it has a utilitarian, no-frills appearance which belies its true capabilities. This thing is built for functionality, not fashion.

Back

Meier Audio Corda Soul SPECIFICATIONS
CONFIGURATION:

Headphone amplifier, a digital-to-analog converter (DAC), and a digital signal processor (DSP) combined into one single device.

INPUT IMPEDANCE:

40k Ohm balanced
20k Ohm unbalanced

OUTPUT IMPEDANCE:

0 / 120 Ohm (headphones)
120 Ohm balanced preamplifier outputs

POWER SUPPLY:

85V to 265V AC / 120V to 370V DC

FREQUENCY RANGE:

DC: 80 kHz analog inputs
DC: (14.5 kHz to 80 kHz) digital inputs
(Upper limit depending on the sampling rate and digital filter selected)

MAXIMAL AMPLIFICATION:

(1 kHz): -6 / +6 dB analog input

MAXIMUM OUTPUT CURRENT:

600 mA per channel

MAXIMUM EFFECTIVE OUTPUT VOLTAGE:

18 Vrms (9 Vrms analog input)
8 Vrms digital input

DIGITAL INPUTS:

Coaxial digital inputs, three
Optical digital inputs, three
USB-B input, one

ANALOG INPUTS:

XLR analog inputs, one pair
XLR analog outputs, one pair

DIGITAL OUTPUT:

Optical digital, one

ANALOG OUTPUT:

XLR analog, one pair

POWER UPTAKE:

20 watts

DIMENSIONS:

11.8” wide x 10” long x 3.6” tall (30.0 x 25.5 x 9.3 cm.)

WEIGHT:

5 pounds (2.7 kilograms)

MSRP:

$3,499.95USD

Website:

Company Site

SECRETS Tags:

Meier, DAC, digital audio converter, headphone, DSP, digital signal processing, DAC Reviews 2021

Design

Back in the year 2000, Jan Meier, Ph. D. founded Meier Audio. Dr. Meier’s company specializes in headphone audio and features a line of portable headphone amplifiers and DACs, and a standalone DAC (the Daccord). Also for sale are custom-made headphone cables, headphone accessories, and headphones built by Focal, Hifiman, and Sennheiser.

Secrets Sponsor

The Meier Audio Corda Soul is a headphone amplifier with two pairs of balanced headphone outputs, one with 120 Ohm output impedance and one with zero Ohm output impedance. It is a digital audio converter (DAC) with one USB, three coaxial, three optical inputs, and one optical digital output. And it is a digital signal processor (DSP), which enables you to do such things as electronically modify the soundstage of a recording or apply notch filters, all entirely within the digital domain with 64-bit resolution.

So, what can it play? The unit can process PCM signals with sampling frequencies of 32, 44.1, 48, 88.2, 96, and 192 kHz, with bit-resolutions up to 24-bit. It cannot process DSD or 384 kHz signals, however.

The USB input accepts signals up to 192 kHz/24-bit and uses the CM6631 from C-Media to receive data in asynchronous mode. These are then sent in SPDIF-format to a WM8804 SPDIF-receiver chip. High-quality temperature-compensated crystal oscillators, or TCXOs, are used to enable jitter-free operation. Then the digital audio signal is fed into an ADAU1451 DSP for all processing concerning the FF technique, crossfeed, channel balance, notch filter, and tone controls. After processing, the digital signal is converted to an analog signal using two WM8741 DAC chips in dual-mono-mode.

The amplifier of the Meier Audio Corda Soul has four separate switch-mode power supplies. One for the digital section, one for the USB section, and two for the positive and the negative supply lines of the analog amplification stage. The output of each supply is RC filtered and further down-regulated with the use of analog voltage regulators. There are separate regulators for the opamps and the buffers. This, together with a total of around 70,000 uF buffer capacity results in extremely stable supply voltages. Sound-critical capacitors are Nichicon Fine Gold.

Insides

Great care has been taken in the choice of the components used in the Meier Audio Corda Soul. Neutrik XLR-sockets, an ALPS potentiometer (although this potentiometer does not carry an audio signal) for smooth operation, LORLIN silver-plated rotary switches, sealed relays, and so on, all contribute to a high life expectancy. This thing is over-engineered and built to last.

On the face of the unit are eight rotary switches for input selection and sound manipulation. There are three two-position toggle switches. There are two balanced headphone outputs. And there are a number of LED lights that glow and change colors to indicate when settings are being changed. A nice touch is a series of blue LEDs which indicate the bitrate of the incoming signal.

On the rear of the unit, you will find a pair of balanced analog outputs, and the standard IEC power cord port. And there is a Toslink output if you want to send the digital output of the Meier Audio Corda Soul to a separate DAC. There is also an XLR analog input on the rear, which allows you to amplify and monitor the incoming signal, but it does not pass through the digital processing. You can use the pre-amp outputs to use the Meier Audio Corda Soul to drive amplifiers or powered speakers.

The entire unit is finished in a soft, matte black with white markings. Silver Allen bolts secure the body plates. It feels sturdy and substantial when carried, runs silently, and generates no heat.

Some lettering on the rear of the component indicates that it’s built by Lake People, which is a company that has been building digital and headphone components for recording studios since 1986. The appearance of the Lake People and Meier Audio components are identical, which leads me to believe the appearance of the Meier Audio Corda Soul lends itself more to life in a recording studio than in a rack of shiny audio jewelry. I rather like the simple styling and found no fault with it. Each selection potentiometer and toggle switch on the Meier Audio Corda Soul has a series of icons printed nearby, and they all made sense to me. So, in essence, the interface of the unit enabled me to interact with it very efficiently.

And, if you use a computer, phone, or tablet for sound, you can send its signal into the Meier Audio Corda Soul through its USB-B input. Worth noting is that if you use an Apple-sourced device, it’s not necessary to load drivers on the source computer. But if you’re using Windows, you’ll have to find and install the correct driver. The unit’s manual includes instructions for this procedure.

One of the knobs on the front of the Meier Audio Corda Soul is a discrete volume control with a typical step size of 0.8 dB in 63 steps. It has a nice sturdy feel to it when you adjust it by hand. Volume control is achieved by changing the feedback impedance in the output stage opamp. This keeps the signal-to-noise ratio high and minimizes background noise and distortion, even at low volume settings. And if you’d like to adjust the volume on the unit from a distance, you can pair an infrared remote control. Full instructions for that are also included in the manual.

And if the gain setting isn’t quite right after you’ve adjusted the volume control, there is a switch to the left of the volume control which enables you to change the gain factor of the amplifier by+/- 6 dB. So, the Meier Audio Corda Soul gives you plenty of parameters to get your sound output just right for your room.

Dr. Meier’s website provides an in-depth scientific explanation of what crossfeed is and how it is utilized in the Meier Audio Corda Soul. He also provides sound files which demonstrate how the crossfeed filter can be used to improve the positioning of instruments on the soundstage, particularly those on the far left or right. Overall, the Meier Audio Corda Soul’s crossfeed filter can greatly improve the timing of the sound arriving from different instruments or voices in the soundstage of the recording, greatly improving the overall coherence of the playback. And when this happens, you can better hear and understand what the people making the music were communicating. I found the web page and the sound files particularly instructive.

To achieve this capability, Meier has to use an extended crossfeed filter that can achieve frequencies above 1 kHz and can reduce frequency delay time from 320 to 160 microseconds. The crossfeed filter has three settings. In the upper (neutral) position the output is plain stereo. Turning the dial clockwise activates the headphone crossfeed (five levels), turning anti-clockwise activates the loudspeaker crossfeed (five levels). The latter widens the soundstage of loudspeakers and is especially useful when loudspeakers are placed relatively close together. In essence, the crossfeed filter allows you to adjust the sound output of the Meier Audio Corda Soul for either headphones or loudspeakers because your ears experience sound differently for both.

A switch to the right of the LEDs allows you to change the filter settings of the DAC chip used. You can choose between classic filtering (phase correct, brickwall) and a filter-mode without pre-ringing (with a slightly softer, more analog sound).

Setup and In Use

It took some time and reading to start understanding what the Meier Audio Corda Soul is capable of, and it was time well spent. And I’m still not sure I’ve experienced everything this component can do. It’s nice to have room to grow with a new component, isn’t it? Fortunately, an in-depth user manual is included; be sure to read through it several times before you put a Meier Audio Corda Soul into your system.

The unit has two outputs for balanced headphones. But in order to listen to single-ended headphones, it is necessary to use a DIN-to-RCA adapter. You can request one of these adapters when you purchase the unit. I had one sent to me with the review unit, in order to listen to my Shure SRH840 and Sennheiser HD6XX headphones. These headphones sell in the $200USD range, so they’re not exactly the caliber of headphones one would typically use the Soul with, but I couldn’t resist trying them out.

Secrets Sponsor

Using the headphone adapter is a bit awkward. You plug one female XLR plug into one of the XLR inputs in the front of the unit, then plug one or both of the other two XLR plugs into the preamplifier output or the analog outputs. This is necessary because the four-pin XLR connector on the front does not have a ground connection, which is necessary for listening to single-ended headphones. And then you plug your pair of single-ended headphones into the 0.25” plug on the adapter.

With all of that done, I listened to those two pairs of headphones with the Soul. And I was surprised at how much better both pairs sounded. They both gave me a sound quality I didn’t know they were capable of, especially with regard to imaging. Granted, I had only listened to these headphones with relatively inexpensive gear, such as a Schiit Fulla DAC/amp ($109USD) or an Audioquest Dragonfly Red ($250USD) with sound sourced from an Apple iPad or Apple computer. I feel like the sound output of the Soul controlled the drivers of the headphones in a much more authoritative way. I heard far greater high-frequency energy, wider soundstage, and tighter bass.

Insides closeup

As for sources, I fed my Oppo UDP-205 and Xbox Series X into the Meier Audio Corda Soul. Over the years, as I have tried new external DACs, I have found Oppo’s sound quality to be a bit cold; it can produce low-level details but does not excel at assembling those details cohesively into naturally flowing music. It was the Schiit Bifrost 2 DAC that first made me realize that using the Oppo as a transport feeding a DAC is the way to go. And using the Meier Audio Corda Soul with the UDP-205 confirmed my belief that the Oppo sounds better as a transport.

I put the Meier Audio Corda Soul into my system as a preamplifier feeding a Krell S5501 integrated amplifier, which then powered a pair of Polk Audio L600 speakers. I’m quite happy with this setup, as it covers the full spectrum of audible sound very well in my listening room, with imagining a particular strong suit. The Polk Audio L600 speakers’ ability to portray deep bass tones with excellent image presentation is something I don’t want to live without. But what has been fascinating for me as this system grows is how imaging has improved and having tight and controlled bass has a lot to do with it. To set a baseline, I listened with only the Oppo BDP-205 as a digital source, then I ran the Oppo through a Schiit Bifrost 2 DAC and that showed me what I had been missing for so long. But the Meier Audio Corda Soul brought the quality and imaging of the sound to a much higher level.

None more black

My most surprising epiphany brought about by the Meier Audio Corda Soul was that it taught me the difference between accuracy and transparency. I learned that accuracy isn’t enough to hear a fully fleshed-out representation of a recorded musical performance. Yes, it is important that a DAC can retrieve low-level detail from a digital recording and send it cleanly to an amplifier, but if the timing of the signals carrying that low-level information suffers in any way, the musical illusion is more difficult to maintain. And the transparency between my ears and the music requires an absence of extraneous sound or noise, and the Meier Audio Corda Soul’s pitch-black background made that possible.

The Schiit Bifrost 2 is an excellent DAC at $699USD, but for what you get in accuracy you trade-off in a slight smoothing of imaging. With the Meier Audio Corda Soul, it sounded like the music signal just flew effortlessly through the circuitry. The Soul was simply not there, but it still managed to open up the music in a way I didn’t think possible. There was no coloration, no warming or softening, or no romanticizing of the signal (unless, of course, you use the unit’s DSP functionality to change the sound).

I do a fair amount of videogaming through an Xbox Series X, and believe if you’re using a quality 4K TV to get the best video quality of a game, the least you can do is use quality playback gear to experience the work the sound designers put into the game. The only digital output the Xbox Series X has is HDMI, so I have to use a splitter to get the Xbox’s digital sound out via HDMI to Toslink into the Meier Audio Corda Soul. (Shame on you, Microsoft, for deleting the Toslink output on the Xbox!) Played through the Meier Audio Corda Soul, games like Borderlands 3 and Doom: Eternal took on a deeper and more immersive experience thanks to the transparency of the sound output. Being able to hear 3D spatial clues in particular actually made me better at the game.

Also, one of my 2020 pandemic projects was to build a streaming server out of a Raspberry Pi. I configured the Pi to run Qobuz via Roon and output digital signals through the Toslink output of a HiFiBerry Digi+ DAC card. That card supports 192 kHz/24-bit sample rates, and when I played music with that resolution through the Meier Audio Corda Soul it handled it with aplomb.

Yes, you can run a turntable through a DAC

One of the biggest surprises I had with the Meier Audio Corda Soul was when I connected my Parks Audio Puffin DSP preamplifier through its Toslink digital output. The Soul happily accepted the Puffin’s 96 kHz/24-bit output and gave the sound of my analog output a depth and energy I did not expect at all. I believe it’s the Soul’s crossfeed filter that did this because it does such a good job of improving how sound from different instruments in the soundstage arrive at your eardrums, and this was particularly and startlingly effective with vinyl playback. If there is such a thing as chemistry between two stereo components, well, these two had it in spades. The Meier Audio Corda Soul made the $489USD Puffin sound like a much, much more expensive phono preamplifier.

An equalizer? Yes, an equalizer!

I’ve heard, over the years and from quite a few people, that using an equalizer is a no-no in a quality sound system. And for the most part, I went along with that assumption. I remember the 24-band, mid-grade equalizers so popular in the 1980s, and I don’t remember one ever really improving sound quality all that much. But the Meier Audio Corda Soul’s four tone controls essentially comprise an equalizer, in that they enable you to optimize the sonic balance to your personal taste. And all of the sound modification happens in the digital domain with 64-bit resolution.

This was a feature I didn’t know I wanted until I used it. For years, I’ve tried to get the best sound quality I could from silver discs. I’ve tried quite a few of the formats: Blu-ray, Blu-spec, DVD-A, SACD, SHM-CD, and so forth. And I have learned that I don’t need a high-resolution format to get good sound quality out of my system. In fact, I find that SHM-CDs sound consistently better than any high-res SACD I’ve ever played in my system.

But that still doesn’t mean that the source material on the CD couldn’t use some improvement. This is especially true with CDs made in the 1980s or source material from the 1960s or later. Using the Meier Audio Corda Soul’s tone controls I was able to fine-tune the sound quality of the rather lackluster mastering of the songs on the David Bowie CD The Deram Anthology 1966 – 1968 (Deram 42284 4872-2, 1997). The instruments, and in particular the studio trickery and sound panning of the recording, exploded out of the sound stage when played through the Meier Audio Corda Soul and Polk Audio L600 speakers, which essentially disappeared. The panning in the song “Join The Gang” was something I had never fully experienced, and it had me laughing out loud. It’s great when a new component gives you sound quality so good that you can better understand the intention of everyone involved in making the music.

Albinoni: Adagio and Pachelbel: Canon

Herbert Von Karajan conducting the Berliner Philharmoniker, Albinoni: Adagio and Pachelbel: Canon (Deutsche Grammophon UCCG 51053, 2016)
Over the years, I have been collecting SHM-CDs from Japan. I find them to be the best sounding Redbook CDs I’ve ever heard. I actually think they deliver the sound quality SACD promised but never delivered. And also, over the years, I have been obsessed with recordings of stringed instruments in classical music. and Tomaso Albinoni’s Adagio In G Minor For Strings And Organ features passages of music played by stringed instruments in tones so pure that I am convinced the sound transcends the physical plane and transforms into pure light and color. The piece ebbs and flows from quiet to loud on numerous occasions, and I want to hear every possible detail and nuance the recording has to offer. Listening to this recording with the Meier Audio Corda Soul enabled me to not only hear each instrument that comprised the sound, but also each instrument’s place on the stage, and how the timing of the notes of each instrument varied according to the instruments’ place on the soundstage. That’s what I mean by transparency; the Soul was so fast it in no way slowed down the timing of any of the notes on the recording, and that added an organic correctness to the playback. It took me a few listens to understand what was going on, because I was hearing not only more low-level detail in the sound but also an overall coherence I had never heard. It did not hurt that the Krell S-550i amplifier had 550 watts of power on tap to take full control of the Polk L600s’ drivers when the music got loud, but then again, the amplifier and speakers wouldn’t have been able to perform that way without the sound quality the DAC was sending it. And now that I’ve heard it, I don’t want to live without it.

Subaqueous Silence

Ayumi Tanaka Trio, Subaqueous Silence (ECM Records ECM 2675, 2021) I listened to this in 48kHz/24bit in Qobuz.
This was one of those pleasant, unexpected surprises from the Qobuz algorithm that kept me mesmerized the first time I heard it. This is improvisational jazz played by three musicians in a profoundly slow and contemplative manner. Piano, bass, drums, and cymbals, whose sum is far greater than their parts. Listening to this music through the Meier Audio Corda Soul enabled me to hear the instruments’ full character burst from a black and empty background. Each musician plays his or her instrument in unexpected but extremely expressive ways. The screeches that bassist Christian Meaas Svendsen coaxes out of his bow and strings are both jarring and gentle at the same time, as he has a musical conversation with Ayumi Tanaka’s stately and foreboding piano. And just as the instruments stop and their vibrations evaporate into the ether, Per Oddvar Johansen will pierce the silence with a carefully pinged cymbal. This album is a tour-de-force for someone who enjoys hearing the marvelous arrays of tones and timbres master musicians can coax out of their instruments, and the Meier Audio Corda Soul enabled me to visualize each instrument clearly on the soundstage. This DAC gave made me feel like I was standing right next to the drum kit. I had never heard such black backgrounds in my home system before. The Meier Audio Corda Soul contributed so much musical information that it enabled the Krell amplifier and Polk L600 speakers to disappear and let just the music come out.

Conclusions

At a price of $3,499.95USD, the MEIER AUDIO CORDA SOUL provides a very wide range of functionality as both a DAC and a headphone amplifier, but it does much, much more.

Likes
  • So many digital inputs!
  • Can be used as a preamplifier with both analog and digital sources.
  • Very transparent sound quality.
  • Enables you to fine-tune the sound output for your room and other hardware in the system.
Would Like To See
  • A more elegant means to listen to single-ended headphones, but this is a very small concern, as it is unlikely the average customer for this unit will be using single-ended headphones.

It can drive essentially any type of headphone, and you can fine-tune the sound output of your system to accommodate everything from speaker size, room acoustics, to poor CD sound quality. You can attach one analog component to it, and use it as a preamplifier. You may think this is more functionality than you need, but it’s quite possible the Meier Audio Corda Soul will show you things you didn’t know you needed. Recommended.

The Meier Audio Corda Soul is expensive but extremely versatile. It gave me the most transparent sound I’ve ever had with a digital source in my system. I was unable to find another DAC/headphone amplifier combination component in its price range that packed as many features as the Meier Audio Corda Soul. It’s not going to be easy to send this one back.