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Review of Meier Audio Corda JAZZ with ƒƒ-technology upgrade

Discussion in 'Headphone Amps (full-size)' started by shoggy, Oct 3, 2011.
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  1. Toad_of_Toad_Hall
    My non-expert understanding is that there can be real benefits to stepped attenuators.

    Volume control is usually achieved by reducing the voltage coming in to your amplifier from your DAC, pre-amplifier etc. This happens by running it through a resistor/network of resistors. Resistors come in all different shapes, sizes, materials, tolerances etc.

    Potentiometers ("pots") are generally much cheaper that stepped attenuators. The former is a variable resistor or voltage divider and often uses something cheaper like carbon to do the "resisting". Whether it's inherent in the technology or a function of material, I'm not sure, but cheap pots can often have poor channel balance at low volume levels: The left side might attenuate the voltage more than the right side. Result? The sound is louder in your right ear than in the left.

    Jan employs some trickery in the Jazz, using a continuously variable contact rotor thingy to control a network of discrete resistors. It feels smooth like a pot, but behaves like a stepped attenuator. Moreover, it uses a series of metal film resistors. Higher quality, better tolerances, no channel imbalance.

    You're the engineer, not me, so correct me if I'm wrong. What type of engineering work do you do? Me? I'm just an underemployed bum.

    btw, MRC001, I've looked at your profile and love your musical tastes. We will have to start an "early music lovers" thread.
    Last edited: Nov 10, 2017
    Wilashort and trellus like this.
  2. VRacer-111
    Understood, the JAZZ-ff has great features with the stepped attenuation circuit and crossfeed - I had very much enjoyed it for quite a while, but was never truly satisfied with the sound. While I would love to keep it for its crossfeed ability, the sound it produces with my selection of headphones just doesn't pair up with them anything like the H10 does. Would have never bought the two H10s if I didn't hear what my modded TH-X00PH sounded like when driven off a high current, massively overkill custom system. That led me to search out highly regarded warm leaning class A amps, and decided on H10 due to cost and wanting to tweak the sound through opamps. I will say that the Gustard equipment does have similar attention to detail like Meier Audio equipment; only high quality components used, very efficient layout with some interesting features, especially for the price, and the sound quality is nothing short of what you would expect ftom much higher end equipment (cost wise). And as good as the H10 amp is, the X20U DAC absolutely floored me over the Schiit Bifrost - very noticeable difference in detail, speed, dynamics, and bass impact/extension.

    I still think the JAZZ-ff is an excellent little amp, and I love the features it has, but it just couldn't meet my needs after finally discovering what kind of amp I needed for the sound I really desired. I really do like the engineering Jan puts into his gear, just wish there was a Meier amp with a warmer sound that could give absolutely MASSIVE, yet phenominal quality bass along with the smoother yet more dynamic and defined mids and highs, which I get with the H10 (modded) and TH-X00PHs (modded) - I would have bought such a Meier amp. My wish would be if he could make a stand alone crossfeed unit that could be placed between a DAC and amp - I would be on something like that in a heartbeat...
    trellus likes this.
  3. MRC001
    Meier licensed his xfeed circuit to Grace, it's in several of their DAC+amps, the m920 and similar models. I don't know if there are others.
  4. MRC001
    I designed and built my own stepped attenuators as part of a passive preamp I built years ago. With only a metal film resistor in the signal path, they're definitely superior to a potentiometer in design & measurements. I admit to being a big fan of stepped attenuators. They're expensive though. Each of the 2 Goldpoint 24-position attenuators I used cost over $100 each and that doesn't count the 96 metal film resistors I carefully soldered into them. But my point was that this doesn't necessarily make an audible difference. And it's possible that an amp that doesn't have one could still be superior to one that does, if that amp has other features to make up for it. Example: Oppo HA-1 versus Corda Jazz.

    That's why the stepped attenuator volume control in the Jazz speaks primarily to Jan Meier's engineering design philosophy and big value for the price, regardless of whether it makes any difference in sound quality (though it probably does).
    Last edited: Nov 13, 2017
  5. Toad_of_Toad_Hall
    @Jan Meier

    Hi Jan

    I'm about to order a pair of HE 560 headphones. On at least one occasion here I've read that the volume needs to be turned up quite high on the Corda Jazz when driving the HE560s and that it's even tolerable at 100% on high gain. While I'm a little skeptical about this claim, it has prompted me to carry out some investigations on the unit I received last week.

    On the high gain setting there is audible transformer hum between 2 o'clock and 6 o'clock on the knob. At least, I assume it's transformer hum. The pitch of the hum is about 50Hz, which is the mains power frequency here in Australia. I have tried the amplifier on a couple of different power circuits around the house and have found the hum to exist wherever the amp is placed, both with and without a source plugged in.

    Here's why I'm concerned about this issue:

    1. I'm quite sensitive to hum, which is one of the reasons why I moved away from tube amps and chose a Corda design in particular
    2. I listen to a large quantity of "classical" music, which can contain a noteworthy amount of quiet passages and even moments of silence (Mozart anyone?)
    3. The HE560s will need to be used on high gain, presumably at a high rotation on the pot.

    I've got a few question for you, Jan:

    1. Do you envisage that I will need to turn up the knob to or beyond 3 o'clock with the HE560s? (Guess this depends on the level of the recording's mastering and source output voltage, but please answer the question in relation to a worst-case scenario)
    2. Is it normal for the Jazz to have the hum I described?
    3. If not, do I have a defective unit?

    Thanks for your help!
    Last edited: Nov 13, 2017
  6. Toad_of_Toad_Hall
    I'm not disagreeing with you, but it seems pointless to a have a component in a piece of audio equipment that makes no difference to the sound (unless it relates to safety). I don't think Jan is the sort of designer who would throw something into his amps just because it looks good on the specs sheet. I'd rather spend my money where it matters and this is one of the reasons why I have chosen Meier Audio in the past.

    Do you think your volume-control design and implementation makes the Jazz sound better than if it used an average quality pot (eg. Alps Blue), @Jan Meier ? In what way? Is the difference barely discernible or relatively significant?
    Last edited: Nov 13, 2017
  7. MRC001
    Regarding your 1st question, this is a matter of degree. There are all kinds of engineering choices that may seem to be overkill, but people do them anyway because they might make an audible difference. For example some people believe all opamps that measure well enough are sonically indistinguishable, so using OPA627s or other fancy expensive ones makes no audible difference. I'm an engineer at heart but I've occasionally reliably detected sonic differences in DBT that were unexpected and had no explanation in measurements. So that makes me less dogmatic about it. If Jan or anyone else goes overboard with the engineering design it doesn't bother me one bit. With so much gear that is under-engineered, it's great to see some that is over-engineered.

    Benefits of stepped attenuators are (1) perfect channel balance at all settings, (2) single metal film resistor in the signal path, which has less noise than a potentiometer. These benefits are measurable.

    Regarding the noise you're picking up with the Jazz... a 50 or 60 Hz hum may come from insufficient stabilization of the power supply, but that's unlikely with the Jazz. It might also come from the inputs picking up interference with nearby power cables. My advice is to move the amp to a different location away from nearby cables or equipment. If the hum goes away or gets quieter, then you have your culprit.

    PS if you get those 560s anywhere near 2:00 at high gain on the Jazz, then you have a higher pain threshold than I do. My old HD580s are less efficient than my LCD-2, and I can't get them anywhere near that level. Of course, that assumes your source is putting out something like 2 Vrms at full scale.
    Last edited: Nov 13, 2017
  8. Toad_of_Toad_Hall

    Oh yes, I agree with you @MRC001 that, in general, stepped attenuators sound noticeably better than pots (although this needs to be tested on a case by case basis).

    I totally disagree with you that something should be added in just because it might make an audible difference. The designer should build, measure, listen, compare, repeating ad nauseum until he gets the sound either he or the market wants at the target price point. That's one of the purposes of prototypes, isn't it? Get in other pairs of ears to see whether they can tell differences between versions and which one they prefer.

    If the profit margin remains the same, "not over-engineering" results in less money spent on the build and a greater value proposition for the consumer. Everyone wins, with the possible exception of gullible people who choose an alternative piece of gear with "over-engineered" features simply because they have heard some random voice on the internet say that "it might sound better".

    Seriously, I say this as a result of unwise and wasteful spending. I've spent hundreds, no, thousands of dollars on film capacitors for amp builds simply because I've read someone's opinion that they might sound better. I'd have been better to spend the money on superior designs rather than on boutique parts of questionable benefit.

    Seriously, we need to talk music! Your tastes are very similar to mine based on your profile. What are some of your favourite renaissance composers? Any recordings you've bought lately that you can recommend?
    Last edited: Nov 13, 2017
  9. MRC001
    In my view, if you want to design top quality audio gear you must use BOTH your brain and your ears.

    : if you can measure an improvement, you should use that design even if you're not sure anybody can hear a difference. Why? Because there will always be more experienced critical listeners with good ears who can hear things you and all your test subjects missed. Or maybe there's a particular type of sound or recording that exacerbates this which you just didn't know about, so it wasn't in your listening trials. Best to be sure and design for the best objectively measurable performance possible. If you don't do this you're on a slippery slope. How much of an inferior engineering design will you tolerate, knowing it is adding noise or distortion just because you can't hear it?

    Ears: if you can hear an improvement, and you've validated you really are hearing it consistently with properly done level matched double blind testing, then use that design. To do otherwise because an engineering textbook, spec sheet, or measurements say what you hear shouldn't exist, puts theory above practice, which is the height of naive arrogance in engineering. We can measure a lot, and some measurements go beyond thresholds of human hearing. But we can't measure everything.

    In short, perfect measuring gear that doesn't sound good doesn't serve the music. And good sounding gear that measures poorly doesn't serve the truth.
    Last edited: Nov 13, 2017
  10. Toad_of_Toad_Hall

    I don't think that the measurements vs sound debate has much relevance in this discussion. I agree that the two are important and often, but not always, seem to correlate.

    There's no question that some people have better ears than others. Personally, I think I'm somehow related to that dude out of The Wizard of Oz, because I have tin ears!

    There's another slippery slope, though: How far do you go down the path of over-engineered audio design?

    Anyway, I'd like to hear what @Jan Meier has to say re the sound of his volume control.
    Last edited: Nov 13, 2017
  11. Toad_of_Toad_Hall
    Already done. Hum persists. Will wait for Jan to respond, but thanks for trying. Or are you really Jan using a secret alias? :wink:

    What do you mean by stabilization of the power supply? Voltage regulation? Sorry, I'm not an electrical engineer (or even anything remotely similar) and am not very good with many of these terms.

    Again, I'll wait to hear from Jan re the HE560 issue, but thanks for chiming in. I'm guessing you haven't heard the HE560 / Jazz combination. The claim I'm referring to was made by someone who professes to have done so.
    Last edited: Nov 13, 2017
  12. MRC001
    I'm not Jan, just a guy who has owned a Jazz for a few years and think it's a great amp. You can email Jan from his web site.
  13. Toad_of_Toad_Hall
    Thanks! Emailed Jan earlier today. Will post Jan's answers here as others might be interested/affected/influenced as well.
    Last edited: Nov 14, 2017
  14. Jan Meier Contributor
    Dear headfellows,

    please be aware that any amplifier will produce hum and other background noises. It simply can not be prevented.

    Important is not the presence of these noises but the signal to noise ratior. Are these background noises audible at normal listening levels.

    With a high sensitive headphone and volume set to high levels hum becomes audible. However, with less sensitive headphones it will not be heard.

    Also important is, whether the test has been done with the inputs of the amp open (capacitive pick-up of net-frequency) or short-circuited.

    With the JAZZ at normal listening levels with any headphone noise is not an issue, promised!


    trellus likes this.
  15. Toad_of_Toad_Hall
    Jan, you are a legend! Thank you. I really appreciate it that you have answered the question both here and directly via email. I can buy the HE560s now with confidence. Communication, as always, is impeccable, fast and extremely helpful. The problem is with my lack of understanding, not the amp. Why doesn't that surprise me?

    I'll go back to enjoying some Frank Sinatra through my W1000Z driven by that Corda Jazz magic. Thanks again!
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