Review and Measurements of Meier Corda Jazz Amp

[MRC01]

The above graph suggests the ground channel is still alive. Yay!
The key is: did the AP difference the Jazz + and - outputs against each other? Or did it leave the Jazz ground output floating, ignore it, and difference the Jazz + output to earth ground?
This depends on how the adapter is wired.

However, after reading Meier's page and doing a little algebra, if the test signal was the same in both channels, then ignoring the ground would not induce any distortion. It would cut the output by 6 dB (half the voltage, 1/4 the power).

 

[amirm]

The key is: did the AP difference the Jazz + and - outputs against each other? Or did it leave the Jazz ground output floating, ignore it, and difference the Jazz + output to earth ground?

The earth ground is not connected to the input of the AP so it is not in play. It is possible the AP's input stage can't handle the negative swings on the common line. Let me see if I can try the balanced input using another connection....

 

[Jimster480]

But so many positive reviews on the other hand? That's what I don't understand. I don't see conspiracy behind that but I certainly see a huge hype on his stuff, with no evidence for quality, until today, when I realized just the opposite.

And how is it never ever someone noticed or reported the distortion at 12 o"click the pot? It doesn't make sense. Some thing is weird here.

I mean just look at the Schiit products... They sounded pretty horrible to me and yet there were great reviews left and right...
When I got my units and didn't like them people told me they were defective... Had them replaced and had the same experiences.

They just sounded worse than the other gear that I had, and at the time I was pretty noob in this scene aswell.

 

[Jimster480]

So much for "German engineering".

Looking at where Benz/BMW/Audi/VW are going, I can't say I'm surprised...

Those brands are all in the toilet aswell. Making vehicles designed to be thrown in the garbage after a couple of years.
Basically "lease only" vehicles... just like Samsung and Apple are both buildings phones for "lease only" as this creates a constant flow of sales.

 

[DuxServit]

So much for "German engineering".

Looking at where Benz/BMW/Audi/VW are going, I can't say I'm surprised...

Well, I don’t think it’s fair to generalize across a nation-wide industry/sector. We’ve had good reviews for RME, for example.

Looking at the Schiit products “Made in the USA” other people could also generalize that the entire US audio sector is going down the shiits— which is simply not true

 

[Jimster480]

Well, I don’t think it’s fair to generalize across a nation-wide industry/sector. We’ve had good reviews for RME, for example.

Looking at the Schiit products “Made in the USA” other people could also generalize that the entire US audio sector is going down the shiits— which is simply not true

There are a few good companies left per country I think... the "majority" have gone to crap I think in almost every sector at this point in time.

I really wish I had the time to open up a "computer science review" website where I could test real performance on computers these days.
There is far too much nonsense in the market (although there is atleast testing going on in some form) and far too much bias from many review sites/channels.

 

[MRC01]

The earth ground is not connected to the input of the AP so it is not in play. It is possible the AP's input stage can't handle the negative swings on the common line. Let me see if I can try the balanced input using another connection....

I'm curious whether that works. However, it seems the best case scenario is a 6 dB improvement to output level and S/N. Overall, that would move this amp up a bit from the low end of performance, but it's not going to challenge the Atom, 789 or Element.

 

[trl]

The transformer is simply too close to the PCB signal input traces and the RCA plugs. Removing it from the PCB and connecting it with wires (at least 2 inches away from the PCB) will solve the mains noise issue. Although, maybe is inaudible...only someone that owns Jazz can let us know that.

I don't see a ground switch to remove the mains ground, so I guess the ground loop eliminator is something similar with Arietta headamp: http://borisgermanov.blogspot.com/2012/05/meier-audio-corda-arietta-headphone.html

​

The active-ground circuit was probably created by 2xBUF634 buffers; something similar here: https://www.head-fi.org/threads/pseudo-balanced-amplifier-pba.553236/. A closer look to the PCB might clear things up, but by looking to https://www.audiosciencereview.com/forum/index.php?attachments/meier-corda-jazz-inside-jpg.24385/ I can spot 4 x BUF634 (2 for left/right channels and 2 for their grounds).

 

[gvl]

I suspect the lack of capitalization in word "designed" is not accidental given the performance.

 

[trl]

Well, I'd really love to see the schematic, I'm sure the design is pretty good, but the increased THD might be caused by the active ground circuitry, while the mains hum is caused by the transformer being placed in the proximity of the audio PCB traces:

"In some low cost Power Transformer designs, a circumferential copper shield (commonly known as a flux band) is applied around the entire transformer boundary. This thin copper flux band reduces ‘eddie’ currents and serves as a radiation shield. Often times it is floating with acceptable attenuation results although it could be connected to the output ground for greater effectiveness", source: https://belfuse.com/resources/white...-ST-Controlling-EMI-in-Power-Transformers.pdf

Talema uses G.O.S.S. band across some transformers: https://www.nuvotem.com/en/products/gossband.shtml, such a transformer might be considered an upgrade in JAZZ's case.

Just my 2-cents guessing: I don't think all the designers & manufacturers have access to at least basic measurement tools to get a proper image of the final product. They probably use the scope for basic electronic tests, then use their ears to evaluate audio quality, which could be fine...in most cases. Maybe it's not the case here, just saying.

P.S.: Some DIY tricks can be applied "locally" to decrease the EMI field generated by the transofrmer, a hint here: https://www.head-fi.org/threads/asu...-dac-cebit-2011.542563/page-211#post-11643158, similar with what Talema did. I learned that trick from a design-engineer from ELECTRA toroid, who actually offered me 0.5m of G.O.S.S. band.

 

[Shaman]

Well this was fun....

I sent this to Amirm knowing things would be interesting. I agree with his assessment that at high volume there is audible distortion and the power is thus limited. At normal volumes it is not noticeable at least for me.

This unit was purchased from Jan directly, it is not his -ff version.

Jan has been at this for a very long time, I think I first was introduced to his porta corda back when most of us where building head phone amps in Altoids tins and chatting with Chu Moy on the forums... Jan is well known and respected, I would be curious about his thoughts on this.

 

[Nango]

Audio-GD also used to place it's transformer right beside the Alps pots which in turn diminish the SQ according to what Amir wrote. Maybe it is here the same flaw.

 

[graz_lag]

... Jan has been at this for a very long time, I think I first was introduced to his porta corda back when most of us where building head phone amps in Altoids tins and chatting with Chu Moy on the forums... Jan is well known and respected, I would be curious about his thoughts on this.

That adds even more frustration, you expect something MUCH better from someone of his caliber in terms of experience and reputation ...

Strange, huh ?

 

[MRC01]

Well this was fun....
I sent this to Amirm knowing things would be interesting. I agree with his assessment that at high volume there is audible distortion and the power is thus limited. At normal volumes it is not noticeable at least for me.
...

Same here. With a standard 2Vrms analog source, and my LCD-2 headphones, I find this amp quite loud at 12:00 on low gain. The distortion Amir measured is audible when you crank the knob past the 2:00 position, but my ears can't take anything approaching that level. Below that level I find it a nice sounding amp.
If Amir gets a connector to his AP that wires in the ground, he'll measure 6 dB better output and S/N, which is at least decent if not spectacular. Just goes to show, ears (even well trained ones) are not always a reliable guide to how something measures.

 

[dudewithcans]

thank you amir for the review. im still waiting for this to come out as an aprils 1st joke (please? pretty please?) or production failure (can exist in multiple devices aswell?) before i complain, especially the output power into 300Ohm on high gain... 30mW? wth? i dont own a meier audio (even though i thought about buying the jazz), but how could noone using it recognize or mention such a low power output on high gain, i dont get this... this CANT be right, right? there MUST be something wrong...

Cant await @amirm testing all that Lake People/Violectric stuff ..............

for reference, theres measurements for the meier audio corda rock and the lake people G109 from innerfidelity, can be downloaded as pdf here:
https://www.innerfidelity.com/images/130219_AmpMeasurements_allamps.pdf

id say the corda rock looks just fine? besides, donno whats right or wrong with the channel crosstalk measurements at all... burson HA160-d -50dB@10k? wut? thats an 1000$ amp from 2010 and the measurement for the G109 says -78dB@15k... lake people specifies -100dB@15k... im uncertain whether to believe that those measurements are correct, or not.

 

[amirm]

thank you amir for the review. im still waiting for this to come out as an aprils 1st joke (please? pretty please?) or production failure (can exist in multiple devices aswell?) before i complain, especially the output power into 300Ohm on high gain... 30mW? wth? i dont own a meier audio (even though i thought about buying the jazz), but how could noone using it recognize or mention such a low power output on high gain, i dont get this... this CANT be right, right? there MUST be something wrong...

I thought about making this an April 1st joke but my funny bone wasn't working so I wrote it seriously.

I am going to return the one unit to his owner and he can verify if it is functional as he gave it to me.

For now, my subjective testing is more stressful than others. I have critical test clips for headphone amps which pushes them to the limit, have two headphones which likewise push voltage and current delivery limits, and I listen (for testing) at pretty high levels. On the latter, I want my reviews to represent the full suite of headphones and tastes (for volume) that people throw at these things. I could hook up my AKG K92 and every headphone would be powerful enough but that is not representative of real world. For these kind of prices, headphone amps need to do it all.

 

[flipflop]

id say the corda rock looks just fine?

Bad frequency response, suspicious channel matching, high output impedance. Doesn't look fine to me.

 

[MRC01]

The Jazz actually has some nice features: perfectly flat FR in audible spectrum, low output impedance, a stepped attenuator volume with perfect channel balance. And if its output is 6 dB louder and cleaner than Amir meausured (due to ignoring the differential ground channel), it's not bad. This would have put it in "Class A" territory 20 years ago, similar to Tyll Hersten's old Headroom amps.
But headphones and amps have improved significantly since then. JDS Labs and the THX 789 really raised the bar, you can get a lot more for your money these days.

 

[dudewithcans]

id say the corda rock looks just fine?
-> Bad frequency response, suspicious channel matching, high output impedance. Doesn't look fine to me.

hmmyes, i agree on the channel matching... but srsly 0.2db will never be heard. ppl tend to forget, what the actual frequency reproduction channel deviation on their headphones! is like (were talking 0.x to multiple dB), right?
frequency response might be "bad" as for measurements, but 0.5dB drop @15k max will not be audible aswell... if you do a blind test and proof to hear a difference between a filter according this FQR and no filter on an actual recording, id hire you for a studio
but i agree, its questionable whether a 250euro hpa should have a better FQR (at least perfectly flat in the audible range) or not... output impedance is 4Ohm and i would not call 4Ohm"high" at all... thats perfectly ok for 32Ohm headphones id say?

The Jazz actually has some nice features: perfectly flat FR in audible spectrum, low output impedance, a stepped attenuator volume with perfect channel balance. And if its output is 6 dB louder and cleaner than Amir meausured (due to ignoring the differential ground channel), it's not bad. This would have put it in "Class A" territory 20 years ago, similar to Tyll Hersten's old Headroom amps.

that is EXACTLY what i think... not mentioned the crossfeed. i use meiers crossfeed filter as VST plugin and i would NEVER ever want to loose it, many recordings sound so much better with it... if your using a CDP f.e. you need a DAC with DSP (and crossfeed function) otherwise, wich will be seriously expensive (question btw: are there any which do not cost a fortune?), or have that option build in with the meier audio amps (though, not variable, only on/off). the ifi audio hpas do some crossfeed aswell on the "3D" setting, right? in the end, the similarly priced micro iCAN does 400mW into 32Ohm, not 300mW like the jazz... well uhmm...

but honestly, the output power on jazz IS really subpar... 30mW into 300Ohm, i still cant believe that. i would not want to pair this with an average sensitive high impedance headphone... maybe a focal utopia would do just fine? j/k

 

[MRC01]

...
but honestly, the output power on jazz IS really subpar... 30mW into 300Ohm, i still cant believe that. i would not want to pair this with an average sensitive high impedance headphone... maybe a focal utopia would do just fine? j/k

You don't have to believe it; the differential ground signal likely wasn't connected when taking the measurement. If so, actual output is twice the voltage and 4x the power, which would make about 240 mW into 300 Ohm, 1.2 W into 30 Ohm, and SINAD about 93 dB.
Still not the best, but not as bad as the initial measurement suggests.

that is EXACTLY what i think... not mentioned the crossfeed. i use meiers crossfeed filter as VST plugin and i would NEVER ever want to loose it, many recordings sound so much better with it...

The worst offenders are some jazz recordings from the 1960s that have absolute L-R separation, like bass in one channel, piano in the other. Some of Pierre Sprey's Mapleshades with his unique triangle PZM boundary mics also have this. On headphones this artificial stereo separation is really annoying. Meier's crossfeed is the best I have heard, and he has licensed it to others (like Grace M902/920 ). I normally don't use it, but for these kind of recordings it is nice to have.