Meier-Audio Corda Rock Budget Headphone Amplifier Page 2

Sonics
So...is it possible to make a small, inexpensive headphone amp that sounds good? As long as you don't ask it to do things it wasn't designed to do, the Rock's answer is yes, definitely. With my two sets of efficient headphones, the Audio-Technica ATH-W3000ANV and the Ultrasone Edition 8 LE, the Rock, well, rocked! (Sorry, couldn't help it, and I'm sure you knew it was coming at some point.)

Taking it in isolation, the sound from the Rock was essentially neutral, with just a very small amount of added warmth, and just a very slightly soft high end. This was not bothersome or intrusive to the music, and is probably the right way to "voice" an inexpensive headphone amp, which is likely to be paired with inexpensive digital sources. Indeed, when comparing the headphone out of my iPad to the iPad's line out connected to the Rock, the latter was significantly better, and this was immediately obvious in a much less strained sound, a generally cleaner and clearer presentation, and noticeably tighter and better defined bass. From that perspective, the Rock succeeds where it should--it's an affordable way to upgrade from the headphone out of something like an iPad. In fact, I also used a Pure i20 digital dock to pull the digital signal off the iPad, and fed its built-in DAC to the Rock, and this was even better sounding, and could be a nice, fairly inexpensive way to get an entry level home headphone set-up.

Used from my expensive sources, though, the Rock sounded even better. When fed the best, the little Rock provided a clean, smooth sound that wasn't audibly flawed in any one dimension. Detail retrieval was admirable, and soundstage was reasonably deep and wide, if somewhat lacking in definition. Bass had good weight, though the very deep bass seemed truncated. Treble was smooth and clean, and the mids were also smooth and essentially transparent. Yes, I have heard better in just about every dimension--but for the relatively low price of admission, the show put on by the Rock was really very satisfying.

All this was using the AT and Ultrasone cans. I tried the Audeze LCD-3, too, and I got acceptable sound, but I really didn't feel that the Rock was swinging enough juice to make the LCD-3 sound at ease. So that is not a combination I recommend. Note that Meier Audio itself sells the highly efficient Sennheiser, Beyerdynamic, and Ultrasone headphones. I don't currently own any Senns or Beyers, but I did very much enjoy the Rock with the Ultrasone Ed 8. The two were more synergistic than the Rock was with the ATs, although that pairing was still remarkably good. But the Ed 8, which are a bit hot on top and fat on the bottom, were well controlled and rendered via the Rock. That was the pairing I came back to most often and found myself really engaged with the music. On occasion I even noticed some things in favorite music I hadn't before--like a very cool keyboard part in a live version of Porcupine Tree's "Trains" that I had somehow missed before. That's always a good sign.

MeierAudio_CordaRock_Photo_InsideTop

Comparatively Speaking
In comparing it to the 4-times-the-price Burson Audio Soloist, it was immediate obvious that these products are in very different classes. The Soloist was better in every conceivable way, and in meaningful and noticeable ways. But the Rock is not intended to compete with something like the Soloist--that would be the domain of Meier's "Corda Classic." Still, it shows that while you get satisfying sound from the affordable Rock, what the little Meier allows is a taste of the good stuff, but not any sort of reference performance.

That said, the Rock's main competition is going to be the fairly large number of combo USB DAC/Headphone amps that are on the market today. The only one of these I had on hand was the much less expensive, USB powered NuForce uDAC. And the Meier is clearly better sounding than the headphone amp section of the uDAC. I connected the uDAC's analog DAC output to the Rock, and the Rock, not surprisingly, drove full-sized headphones better than the uDAC. I think the Rock would appeal to a much broader market if it had a USB DAC built into it. Then again, it would obviously cost more, and where a USB DAC isn't really needed the Rock provides very good headphone sound for its relatively small asking price.

Summary
Reviewing "budget" gear has become hard for me. I listen to headphones that START at $1,200, and with amps that start at $1,000. That is my daily diet of headphone listening. When something like the Rock comes along I have to put it into context. Does it give the user a satisfying listening experience? Absolutely. Is it money well spent? To me, it sure is. Can you get better performance? Of course you can...if you are willing and able to pay for it. But not everyone can, and in the current economic environment it's nice to see that there are affordable choices. Meier Audio comes with a 14-day return policy, so trying one is a fairly low-risk proposition. But I doubt you would be disappointed. I wasn't. I applaud Meier for designing such a capable product at this price point.

Resources
Meier-Audio home page and Corda Rock page.
Short Rock thread on Head-Fi.

COMPANY INFO
Meier-Audio
Am Tennenbach 20
91080 Spardorf
Germany
meier-audio@t-online.de
+49 9131 532418
ARTICLE CONTENTS

COMMENTS
Eric_C's picture

Hi Tyll, one very slight correction: the Rock has 2 inputs (non-switchable). There's the obvious pair of RCA jacks, but also an unlabelled 1/8" next to the RCA.

I understand that gain can also be tweaked via jumpers at the bottom, though for the life of me I haven't figured out how.

Skylab's picture

You're right about both - I didn't mention these because I didn't use the 1/8" jack, and the amp to me sounded universally better in Hi-Gain mode.

Eric_C's picture

Oops, sorry Skylab! Didn't mean to address you as Tyll.

The Rock is set on hi-gain by default, right?

Skylab's picture

No worries :). And yes, comes on hi gain mode, and jumpers on the bottom are used to change.  

Jazz Casual's picture

Hi Tyll,

What do you think of the W3000ANV and will you be measuring it?

Tyll Hertsens's picture

Haven't heard it. Wonder if HeadRoom has one. I'll check.

Jazz Casual's picture

I've not seen it listed on the HeadRoom site but hope that you can get your hands on one. People who cannot tolerate the W5000 are enamored with the W3000ANV. 

Isawelvis's picture

Any comments on how it compares to something in the same price range lets say, the Schiit Asgard?

Skylab's picture

Thanks! Unfortunately I don't have anything else on hand in that price range to compare it to, currently.

Jazz Casual's picture

Sorry Skylab, I should have looked more closely. No need to ask what you think of the W3000ANV. ;-)

donunus's picture

Any impressions against the jdslabs O2?

Skylab's picture

I will be getting an O2 from Tyll to review, so I will have an opinion on that at some point in the near future.

donunus's picture

Thats great to hear. Thanks

Skyline's picture

At this price, can it really compete with something like the Asgard which sells for about the same amount?

FLAudioGuy's picture

Meh, I'll keep my O2.  For the money, I see a lot of things I don't like in the Corda Rock. To start with, those two Myrra 47155's. They may look like trafos but they aren't. Those are actually SWITCHING MODE POWER SUPPLIES! This means they work at much higher switching frequencies. This also means that you will need very careful PCB routing and Low ESR capacitors. The "For Audio" caps will not perform very well here. They can not effectively suppress the high frequency ripple caused by the PSU switching elements. You can see all the noise in the plots. Additionally, they are quite expensive (USD12ea from USA distributor Newark) even in bulk, even in China they are not cheap in the quantities Meier must be purchasing at. So, around $24 just in the PS? IMO, waste.

What about that big blue Alps RK27 volume pot? Even with this highly-touted pot it has higher channel imbalance than the O2. 100KΩ = higher Johnson noise than the O2's 10KΩ RK097 pot. IMO, more waste.

The TDA2030 used in the Rock is a LF power amplifier with output stage running in class B or AB. This one has a low quiescent current of about 40mA, hence the lack of heatsink except the front plate. Since Meier is using it to power headphones, not speakers, the Myrra "electronic transformers" may be just fine except for the noise.

With a 4Ω+ output impedance the Rock is 8X higher than the O2. That means on an 80Ω headphone the Rock has a damping factor of 20, while the O2 has 160. For 300Ω cans, it would be 75 versus 600. IMO, meh.

Overlay the graphs for yourself, there isn't any substantial area where the Rock performs better than the O2. 

In comparison to the rest of the Meier lineup, this unit isn't particularly handsome either. The O2 can get away with some "ugliness" at it's price point and the fact it was designed as proof-of-concept and to be DIY friendly. But Meier sells the Corda Rock as a finished consumer-ready unnit at $240.00. IMO, just plain not good enough.

Jan Meier's picture

" For the money, I see a lot of things I don't like in the Corda Rock. "

Beauty is in the eye of the beholder!  :-)

" those two Myrra 47155's. They may look like trafos but they aren't. Those are actually SWITCHING MODE POWER SUPPLIES! This means they work at much higher switching frequencies. This also means that you will need very careful PCB routing and Low ESR capacitors. "

Within a small enclosure switching mode supplies have big advantages. The magnetic fields of the trafo are much smaller and at frequencies outside the audio-band. Therefore induced hummmmmmmm is much lower.

Of course one has to take care that the high-frequency noise doesn't reach to the powerlines. But that's well possible using inductors between powersupply and buffer-capacitors.

" Additionally, they are quite expensive (USD12ea "

And what do a toroidal transformer, fuse, 110/220V switch, buffer capacitors, rectifiers, voltage regulators, ... cost? They are all replaced by these two power-units!

" big blue Alps RK27 volume pot? Even with this highly-touted pot it has higher channel imbalance than the O2. 100KΩ = higher Johnson noise than the O2's 10KΩ RK097 pot."

The RK27 over most of its range has better channel balance than the RK09 series. Read your specs!

The potentiometer on the ROCK has 10 kOhm!

" The TDA2030 used in the Rock is a LF power amplifier"

Yep, that's why it has so little distortion at high output levels and such a high voltage swing! Actually it's the TDA2030AV, which is better sounding than the TDA2030.

" with output stage running in class B or AB. This one has a low quiescent current of about 40mA"

The quiescent current of the output stage of your beloved O2 is much lower.

Let's say the TDA2030AV runs into class A upto around 30 mA. That means upto 8V with a headphone like the HD800. And even with a 30 Ohm headphone this implies class-A performance upto around 1V. Enough to make your ears bleed!

" hence the lack of heatsink except the front plate."

Without this heatsink the TDA2030 would not survive.

Does the O2 have a heatsink this size, if any at all?

" With a 4Ω+ output impedance the Rock is 8X higher than the O2. "

Can you give me values for some tube-amplifiers?

" there isn't any substantial area where the Rock performs better than the O2. "

Voltage swing!?

Compare Tyll's measurements for the ROCK to those of very well respected amplifiers like the HA160D, the G109, and the EF6 and I think the ROCK does very well, especially considering its size and price.

" this unit isn't particularly handsome either."

Again, beauty is in the eye of the beholder. I know of many people who like the looks of this amp. It's all very personal.

Cheers

Jan

Jazz Casual's picture

I love reading rebuttals like this. :)

Theogenes's picture

...but it was worth it to read such an informed reply from the source himself. 

And for the record, I think it's sharp-looking. Dressing it up to look like D'Agostino amp would've looked great, but completely defeated the purpose of a low-cost amp like this. 

thaddeus's picture

Cool reply from Jan but where are the measurements to compare to the O2?

thaddeus's picture

I found it thanks to someone's help!

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