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Review and Measurements of Meier Corda Jazz Amp

amirm

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#1
This is a review and detailed measurements of the Meier Audio Corda Jazz headphone amplifier. It is on kind loan from a member. The Corda Jazz costs USD $355 from the company direct.

Given the inclusion of an AC mains power supply, the Corda Jazz feels quite hefty for its size:

Meier Audio Corda Jazz Headphone Amplifier Audio Review.jpg

No, you are not seeing double. I actually received two identical units for testing!

I find the graphics preminative and unattractive.

Other than the usual low and high gain, there is a cross-feed button which I did not play with.

The headphone socket is a Neutrik and mates nicely with 1/4 inch headphone jacks.

The back panel is as simple as you can get with AC IEC connector and a pair of RCA jacks:

Meier Audio Corda Jazz Headphone Amplifier Back Panel Audio Review.jpg
I​
I am not one for detail as you can tell from my posts but come on: why is "designed" not capitalized?

Measurements
I started with my unity gain test of 2 volt in and 2 volt out:
Meier Audio Corda Jazz Headphone Amplifier Audio Measurements.png


The volume control is analog but is digitized using an ADC which in turn selects 32 steps in output gain. So I couldn't get it to 2 volt exactly.

Our SINAD (signal over noise and distortion) is a disappointing 87 dB or so. If we look, the third harmonic is the worst offender at -98 dB. So why is our SINAD 10 dB worse? It is because of massive mains spike at 60 Hz and its harmonics which are some of the worst I have seen. Curiously the spec says it has some kind of ground loop eliminator:

1554103163969.png


I played with input grounding but it made no difference whatsoever. Even though I usually don't play with headphone out grounding, I was warned to not attempt that in this case anyway due to the ground wire actually carrying a signal of its own. So we have what we have.

Updating our table of headphone amps with the Corda Jazz SINAD value we get:

Meier Audio Corda Jazz Headphone Amplifier SINAD Audio Measurements.png


Signal to noise ratio is limited by the mains noise as we could predict:
Meier Audio Corda Jazz Headphone Amplifier SNR Audio Measurements.png


Measuring the same with 50 millivolts gives us this:
Meier Audio Corda Jazz Headphone Amplifier SNR 50 mv Audio Measurements.png


I need to fill this table with our better performing amplifiers.

Frequency response was flat enough to 20 kHz but then took a dive above 30 kHz:
Meier Audio Corda Jazz Headphone Amplifier Frequency Response Audio Measurements.png

In the age of high resolution audio, I like to see flat response to 40 kHz and higher.

Intermodulation test was totally nutz with volume control at max as I normally test. Distortion skyrocketed early in both low and high gains. I dialed the volume control back to about 2:00 o'clock and that fixed most of that at the expense of slightly higher noise floor:

Meier Audio Corda Jazz Headphone Amplifier Intermodulation distortion Audio Measurements.png


Strangely, high gain did not do anything better than raise distortion level above .3 volt input (pink). There is some design error here.

Measuring power versus distortion and noise did not do much to make me happy:
Meier Audio Corda Jazz Headphone Amplifier Power at 300 Ohm Audio Measurements.png


These are dismal power output levels. That aside, what the heck is wrong with low gain mode? Why is it clipping? Low gain mode is supposed to stress the amp a lot less with lower voltage output so there is no reason for it to badly clip.

High gain has much elevated noise likely due to the mains noise shown in the dashboard. The gap to our reference $99 JDS Labs Atom is massive.

The same ugliness continues with 33 ohm load:

Meier Audio Corda Jazz Headphone Amplifier Power at 33 Ohm Audio Measurements.png


Output impedance was excellent at just 0.9 ohm:

Meier Audio Corda Jazz Headphone Amplifier Output Impedance Audio Measurements.png


Channel matching was perfect too due to digital control:
Meier Audio Corda Jazz Headphone Amplifier Channel Balance Audio Measurements.png


Listening Tests
I plugged in my Sennheiser HD-650 headphones into Corda Jazz expecting the outcome to disagree with the measurements. That was not to be the case. Up to 12:00 o'clock on the volume control all was OK. But going much past that caused severe distortion in both low and high gain modes. The latter was not remotely sufficient for this headphone. The distortion was not subtle at all. It reminded of my first car which would accelerate a bit and then the engine would stall due to improper ignition timing.

The situation did not improve at all with Hifiman HE-400i. Distortion was ready and present at any decently high level of playback.

Conclusions
I was so happy to have two of these amps as after seeing such disappointing measurements from a German audio company, I did a spot test on the second with the same performance. The Meier Audio Corda Jazz is a flawed design with multiple issues both objectively and subjectively. That it costs so much money simply adds insult to injury. The only way you can escape its very low limits of performance is to use very efficient headphones with it. In that case, you may be better off buying a $9 dongle instead of spending hundreds of dollars on this unit.

The fact that there is not a single measurement or specifications of any kind (not even power output!), should have been a give away that this device will likely have performance performance. I wonder if it was measured at all. Even if not, how did listeners not notice the lack of power and quick onset of distortion? I searched and the only reviews I found were the fluff kind with soundstage this, and detail that, missing the major weaknesses in this product.

Even if the design was performant, it simply is not competitive with what is in the market now in the form of JDS Labs Atom and Massdrop THX AAA 789. These two amps have completely changed the landscape of headphone amplifiers with exceptionally low noise and distortion while producing tons of power. To continue selling headphones amps with far less power and more distortion and noise for same or much higher price is like trying to sell flip phones for more money than smartphones. These people should buy an Atom and see what they are up against.

Needless to say, I see no reason to recommend Corda Jazz headphone amplifier.

------------
As always, questions, comments, recommendations, etc. are welcome.

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Dro

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#5
Very disappointing. Meier has a very good reputation. Looks like it might be undeserved.
 

graz_lag

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#7
It seems there is no Jan Meier signature sticker, are the above fake units ? ;)

IMG_20190401_140328.jpg
 

flipflop

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#8
I thought a DAC was necessary for a device to have digital volume control. Guess not.

Would you mind measuring the other unit? I'm interested in how large unit to unit variations in amps can be. When it comes to headphones, some models show drastic differences in performance between units.
 
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#10
I thought a DAC was necessary for a device to have digital volume control. Guess not.

Would you mind measuring the other unit? I'm interested in how large unit to unit variations in amps can be. When it comes to headphones, some models show drastic differences in performance between units.
It has a cheap carbon pot with a lot L/R deviation.
 

Veri

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#11
I thought a DAC was necessary for a device to have digital volume control. Guess not.

Would you mind measuring the other unit? I'm interested in how large unit to unit variations in amps can be. When it comes to headphones, some models show drastic differences in performance between units.
In the conclusion Amir says the other measured /w same performance.
 

MRC01

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#13
Even though this amp has an unbalanced output jack, the ground carries a signal similar to a balanced output. It operates with differential signalling that Meier calls "active balanced ground driving" http://www.meier-audio.homepage.t-online.de/grounds.htm

Thus it should be tested as if it were balanced. Is it possible the poor distortion performance was caused by the test rig ignoring or grounding the ground output? This would drop half the signal and overdrive the amp's output stage.
 

Nango

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#15
Even though this amp has an unbalanced output jack, the ground carries a signal similar to a balanced output. It operates with differential signalling that Meier calls "active balanced ground driving" http://www.meier-audio.homepage.t-online.de/grounds.htm

Thus it should be tested as if it were balanced. Is it possible the poor distortion performance was caused by the test rig ignoring or grounding the ground output? This would drop half the signal and overdrive the amp's output stage.
He says, "severe distortion passed 12' o clock" no matter if balanced or non-balanced or Jan Meier's balanced mode ......?
 

dreite

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#17
Even though this amp has an unbalanced output jack, the ground carries a signal similar to a balanced output. It operates with differential signalling that Meier calls "active balanced ground driving" http://www.meier-audio.homepage.t-online.de/grounds.htm

Thus it should be tested as if it were balanced. Is it possible the poor distortion performance was caused by the test rig ignoring or grounding the ground output? This would drop half the signal and overdrive the amp's output stage.
Why does the unit not have a balanced output jack then? This would seem an obvious design error.

Dave.
 

MRC01

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#18
Meier, the designer, says the goal is to provide some of the benefits of balanced without the expense of recabling your headphones.
If you measure this amp as if it were unbalanced, then:

1. You'll short the ground channel, overdriving it into distortion, possibly damaging it.

If you let the ground float, you may avoid damaging the ground channel driver. But even so:

2. You'll measure about 1/4 the actual power output, since the signal will be cut in half.
3. You'll measure a lot of distortion because the L + wire carries a mix of L with R out of phase (and vice versa), since the ground isn't there to difference it.

How do I know? I made this mistake myself a few years ago when measuring this same amp! I contacted Jan about the problems I measured and he told me how to do it right.
 

amirm

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#19
3. You'll measure a lot of distortion because the L + wire carries a mix of L with R out of phase (and vice versa), since the ground isn't there to difference it.
My issue is twofold:

1. He doesn't provide any measurements. If he had, then we could reference those and use similar fixture.

2. I listened to the headphone. It clearly lacks power and gets distorted precisely the way the measurements predict. There simply is not four times the amount of power available.

I did see that the output is 15 volts which I am NOT seeing. So I buy that there is some kind of inverse signal on ground but bottom line is that my analyzer in floating mode, is measuring what a headphone sees. Perhaps he is throwing away half the voltage to solve some problem unrelated to power delivery.
 
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