Why do these Zyx Fuji and Airy 3 have such a dark sound?

Hi everybody.
I only have around 24 hours for this, so I’m posting this last minute. Sorry about this. I’ve also posted this on Vinyl Engine.
Before I go into details, this is my question:

To anybody who owns a Zyx R100 Fuji S or a R1000 Airy 3 X (or similar models), does your cartridge sound "dark" like I describe below (a big dip in the treble)? Sound clips are provided at the end.

Okay, here I go. This is long, so I hope you can cope with all the details, as they are necessary:

I have these two cartridges on loan (and I have to return them tomorrow) because I had previously downloaded vinyl rips done with these two carts, and I really, really liked the sound of those vinyl-rips. The carts seemed quite accurate and neutral and as if they had a fairly flat frequency response and without harshness, which is what I was looking for: Not a "typical" dark MM sound, nor a "typical" bright MC sound either.

So, this is where the trouble starts:
The downloads don’t sound like the recordings I’ve made myself with the same carts! Some people call Zyx carts too bright, but it’s as if the treble is missing on my recordings when I compare to the downloads. It’s possible that I just don’t like these carts after all, but it’s strange that the downloads all have the same sound signature even though they’re from different uploaders using different systems, which would indicate that nothing would have gone wrong in the recording or uploading process.

I think there are four possible explanations to what I describe below:
1: My recordings sound like these carts are supposed to sound like, and I just don’t like them.
2: Something has gone wrong in all of the downloads I mention.
3: None of the phono stages used for the vinyl-rips I mention follow the riaa curve, but are all top-heavy by several dB.
4: All three Zyx carts (yes, three, see further down) are faulty

So, I’m wondering if I’m doing anything wrong, or I can adjust some settings to achieve the same sound as the vinyl-rips I downloaded. I feel like I have literally tried EVERYTHING there is to try. I read that Zyx carts are very sensitive to setup, but no matter what I’ve done, the sound hasn’t changed, except for a slight change in channel balance. I’ll elaborate about this further down. One thing I did notice was that both the Fuji and the Airy were very loud when I stood next to the turntable and listened to them play "acoustically".
Yesterday, I took the Airy to an acquaintance’s place and tried it on his turntable, which was an old Thorens with a Mørch UP4 tonearm. He used PSB Imagine T2 Tower speakers. We both agreed that the recordings done on my setup were identical to how it sounded on his setup, except maybe that there was a slight speed discrepancy.

Here I can also interject that I’ve also been trying out a Goldring 2500 cart at the same time, and that was too bright for me, and even brighter than certain digital 16/44.1 kHz masters that the records had been cut from. So trying that cart, as well as trying the Zyx on my acquaintance’s setup, would rule out that there’s something wrong with my turntable or preamps.

And the last aspect that can rule out that my equipment is the problem is this: Before borrowing the carts, I went to the shop and made a recording (with my own phono preamp with its built-in convert) of the new Zyx Ultimate 100 on their setup, which I’m quite certain was an Acoustic Signature Wow XL or XXL turntable with an Acoustic Signature TA-1000 tonearm. That recording was even darker than the one done with the Fuji on my own setup. The shop also said that the Fuji was a bit brighter than the Ultimate 100.

I use my headphones and Foobar’s ABX plugin to compare my own recordings with the vinyl-rips I downloaded, so even if my headphones were broken, I would be able to hear the difference between my own recordings and the downloads (like I could at my acquaintance’s place yesterday).

Here’s my setup:
* Sennheiser HD650 headphones
* Rega RP3 with an RB-303 tonearm (2013 model)
* NAD PP-4 phono preamp
* Parasound Zphono preamp
* Also a Soundsmith MCP2 MC phono preamp with adjustable ohm loading that the shop lent me. I’ve ONLY used this on the Airy. When loaded with 100 ohm, like the NAD and the Parasound, the only difference I could hear between the Soundsmith and the NAD, was that the Soundsmith was a bit darker sounding. The Parasound is also a bit darker than the NAD. Feel free to read the excellent measurements of the NAD PP-3 on Stereophile’s website. The maximum deviation from the riaa curve is 0.25 dB. When increasing the ohm load to 1000 ohm on the Soundsmith, the treble became more prominent but still not to the same extent as on the downloads. After 1000 ohm it didn’t seem to change any further. At 10 ohm I didn’t hear any difference to 100 ohm. It just seemed strange to me that I had to increase the ohm load that much, when 100 ohm is the standard and when I read that people use less than that for Zyx. Also, the phono stages used in the downloads are not all able to even go to 1000 ohm (nor was it mentioned that the ohm load was that high). I am of course aware that comparing to a random download is not the perfect way to do it, but still… As mentioned, all the downloaded vinyl-rips have the same sound signature.
* Focusrite Scarlet 2i2 A/D converter
* Objective2 + ODAC headphone amp and DAC
I’ve recorded with both the Focusrite converter and the built-in converter in the NAD and I couldn’t tell them apart in an ABX test.

So, these are the settings I’ve been experimenting with:
* Protractors: I’ve printed three protractors: The Baerwald and Stevenson protractors from Vinyl Engine, as well as the Arc Template Generator that Conrad Hoffman made (I used Bearwald for that one as well). I couldn’t hear any difference on any of them, except for one recording with a slight difference. I’ve also tried pushing the cart 1 mm forward or 1 mm back, pushing it all the way forward into the headshell or pulling it all the way back, turning it a bit towards the spindle, or turning it away from the spindle. It didn’t make a difference except for a bit on the channel balance. With my Rega Exact cart I passed blind tests between a Baerwald adjustment and the "factory" setting with three screws (the Baerwald was brighter). In the shop, they adjusted the Ultimate 100 with a Dr. Feickert protractor.
* VTA: I could hear a small difference, but big enough to pass a blind test, between a recording where I raised the arm 6 mm, and one where I put two records beneath the mat, so it would be very much tail down. However, not much of a difference. I also heard the same difference with the Goldring (raised was brighter).
* Counterweight. I’ve tried going from 1,50 grams up to 2,50 grams. I’ve tried Art Salvatore’s recommended 1,85 grams, the recommendation of 1,95 grams from another, 1,79 grams, and pleeeeenty of other combinations, but I would mostly use 2,00 grams. No difference.
* I’ve tried to loosen the screws that bolt the cart to the arm a bit. No difference.
* I’ve used a bubble level to check azimuth (I then adjusted my arm a bit). No difference.

Lastly, you might think that the carts just need to break in. I thought so too, although I’ve always been a bit sceptical about break-in. Anyway, the Airy already had some play on it, and I was actually given another Fuji to try out, and it was well-used, but that one sounded even a bit darker (just worn, really). On top of this, the way I understand break-in is that before a cart is broken in, it will sound harsh and bright – the opposite of what is the case here. But if Zyx carts get a more prominent treble after breaking in, if breaking-in even exists, then this could be the explanation.

So, on to the sound clips:

I have uploaded the following clips recorded with the following equipment (all of my recordings are done with the Focusrite converter), and yes, the albums are all the same editions from the same countries (I always make sure of that):

1: AC/DC "Rock or bust", done with my Rega, the NAD preamp and the Zyx Airy, then the same setup but with the Soundsmith set to 1000 ohm, then the CD, which I believe is the same master used for cutting the record, then the vinyl-rip that I downloaded, which sounds quite close to the CD, done with the following equipment: Micro Seiki DD-8 + ZYX R100 Fuji S, PS Audio GCPH Phono Stage + Tube Preamp (Telefunken tubes 3xE88CC), TASCAM HS-P82. Lastly, a vinyl-rip download to compare, recorded with a Micro Seiki DDX-1000 / Micro Seiki MA-505L, Benz Micro Ruby Gullwing SHR, Past Audio C-7Super (Deluxe Edition), and M-Audio ProFire 610.

2: Marilyn Manson "Deep six" (from "The Pale Emperor"), my own recording with the Airy and NAD, then also with the Zyx Fuji and NAD, then done with my Rega Exact cartridge and NAD (I did, however, adjust the channel balance on my computer, as it was off, partly because the cart was made that way, and partly because the arm on my own turntable at the time was not mounted completely straight), then the recording from the shop done with the Zyx Ultimate 100 and NAD (detailed above). I had to adjust the channel balance here as well. And then lastly two vinyl-rips I downloaded, done with the following: 1: Pioneer PL-7L + ZYX R100 Fuji X, PS Audio GCPH Phono Stage + Tube preamp + Tascam HS-P82. 2: Garrard 401, ZYX Airy 3, Trilogy 907, Korg MR-1000. These two downloads sound quite similar.

3: Chris de Burgh "Take it to the top" (from "Man on the line"), my own recording with the Airy and NAD, then a vinyl-rip download done with a Garrard 401, ZYX Airy 3, Sentec/Nebula (A), and Korg MR-1000.

4: Queen "Self-titled" (re-release on Fame) my own recording with the Airy and NAD, and a vinyl-rip download done with Garrard 401, ZYX Airy 3, Sentec/Nebula (A), and Korg MR-1000.

5: Mastodon "Black tongue" (from "The Hunter") my own recording with both a Fuji and an Airy and the NAD, and then with an Airy and the Soundsmith set to 1 kOhm, and then a vinyl-rip download made with Micro Seiki DD-8+ZYX R100 Fuji SH, PS Audio GCPH Phono Stage + Tube Preamp (Telefunken).

LASTLY, since I figured that most of you wouldn’t have any of these albums, I have included recordings of two albums you might have, so you could compare:

Dire Straits "Brothers in arms" and "On every street" (both original EU prints).

I only have my own recordings of these, but I know that they’re both cut from digital 44.1 kHz masters, and my recordings are not very close to the CDs. The Goldring cart was brighter than the CDs, since it seemed to have a big spike in the treble.

So, here are the downloads:

I hope this doesn’t sound offensive, but I’ll just say this to avoid any potential arguments and that people waste their time writing a lot of things: As you might have noticed, I’m a no-nonsense guy, so please no suggestions like "digital is crap", "you’re deaf", "buy a different turntable", or "buy brand X phono stage" or "buy new interconnects" or "buy a Nordost power cord" or "these carts are not good for that type of music" or whatever, because it’s besides the point, I’m not going to buy any of that, and I’m not I even going to debate it.

Anyway, I appreciate any and all help :-).
Thanks, and thanks for reading through all this!
Post removed 
So, you've tried everything. Looks like it is a dark sounding cartridge. 
Try a 47K ohm load.  It's really impossible for a third party to make your diagnosis, because we don't know how your system ensemble sounds or what you really mean when you say "dark".  This is not your fault, necessarily.  It's just that none of us can be in your listening room with you.  As you say, ZYX cartridges are generally NOT "dark" sounding.

Please confirm or dispute my summary of the very long post:
(1) You are auditioning these cartridges based on the fact that you listened to vinyl rips made from them.  By "vinyl rips", I presume you mean digital copies.
(2) You are now comparing your own digital copies made from LPs played in your system, and the digital copies are dark sounding.

I really have not tried to read every word of your post, but by scanning it, I don't see that you have made any comment about how the cartridges sound when you actually listen to the analog output direct from your system.  One question would be, how does the direct analog sound compared to the original digital copies that caused you to want to audition the cartridges?  Why are you confining yourself to a comparison of digital to digital?  Or am I missing something?

Sometimes, even LOMC cartridges sound more open, more extended in the treble, when you reduce the resistive load, which is why I suggest that you listen at 47K ohms.  If you're using a SUT, you really cannot do that, I know, but you don't list a SUT among your components.
There was something that I had forgot to mention that I had already tried: Put it through the MM stage instead of MC. I tried it again now. No difference (except for the amplitude, obviously).
Also, I've (obviously) also tried the Parasound and Soundsmith phono preamps, which just make the sound a tad darker.

Yes, I’m comparing my recordings to recordings of the same albums done by other people who then uploaded them to the web.
As mentioned, the rest of my system is in storage, but the digitazation is not the problem: I listened through my acquaintance’s speakers, I’ve tried two different converters, the Goldring cart was much, much brighter, and lastly, a digital converter can’t change the sound in this way, unless you have a seriously faulty converter from 1972 or something.
Let’s simplify this quest a little bit. First, please tell us which cartridge is not dark in your system? I have owned Zyx Aity 3 Silver Coil and this it NOT DARK sounding cartridge at all for sure (compared to many cartridges). Such a low impedance cartridges are not sensitive to loading. You need some break-in time, but not too much (i’m also sceptical about break-in as the way to change the nature of sound much).

Let me ask you one thing:
Are you sure your ZYX is not a grey market samples?

Do yourself a favor, listen to the actual vinyl in your system, compare cartridges by playin the same favorite LPs (with different carts). Forget about your vinyl rips if you want to make sure about the actual sound of your cartridge.

Borrow some nice prono stages or SUT if you don’t like the sound with your own phono stages. I have some amazing headamp made by ZYX for their cartridges, if you could find a borrow it - try it. The model called ZYX CPP-1 active pre-preamp (connect it to MM phono stage, 47k).

Maybe you have a faulty samples of your ZYX models, they are old and out of production, discontinued models. Your distributor (company) name is the official ZYX distributor in your area or just a re-seller ? Beware of the old ZYX coming from grey market dealers on ebay! Do you have valid serial numbers on your samples that you can check with the real distributor?

ZYX may be not your type of sound even if the cartridge is fine, but they are definitely not dark souding cartridges, i’ve owned Airy III (Silver Coil) and Premium 4D (Copper Coil). The 4D is better than the Airy.

 I enjoyed a ZYX R100 Yatra for several years. I know its not an R1000 but they share many characteristics. I intermittently  experienced what the OP describes as rolled off high end.  Look no farther than your tonearm.  I could not get it to sound right in a Jelco 750 but it really opened up in an Audiomods and a Mørch DP-6. If I used too much weight in the head shell (like using brass Sound-Smith mounting screws) it became dull. These carts are also sensitive to VTA, VTF.  Hope you find the right combination!
Have you tried playing a test record? Because, if you are used to digital, a good analogue sound might seem lacking in treble.
Also, I would like to second Karl's comment. Setup is critical, down to matching the torques on the cartridge screws.
I know my original post was very long, but it’s still a bit sad that people couldn’t be bothered to read it and then instead started posting things that I had already mentioned in my original post.
It seems like no current owners of the cart has downloaded my soundclips and listened to them, which was what I had hoped for to begin with. Obviously, I know it’s unlikely that an owner of one of these carts happens to see this post and has time to listen to my sound clips since I had less than 24 hours before I had to return the carts.

So, just to repeat (all of this is in my original post):
* My system is in storage, so I can’t listen through my speakers, but I listened through my acquaintance’s PSB speakers.
* My acquaintance’s used a Mørch tonearm, and we both agreed that the Zyx sounded identical on his system to what it did on my recordings. Also, in the shop they had set up the Ultimate 100 on an Acoustic Signature tonearm, and that combo also had a dark sound.
* Digitization can’t change the sound that much, and I’ve tried two different converters as well. Please, no more digital bashing. This is not the issue.
* None of the adjustments I’ve made has changed the sound, except for a tiny bit with VTA (but still not enough).
* As I also said in my original post, I’m not going to buy or borrow another phono preamp. There’s no time for that, and it’s not the issue either, since I have already tried three different ones, including the Soundsmith MCP2 with adjustable ohm loading, which brought out the treble a bit more, but still didn’t fix the issue.
* A bright cart in my system was the Goldring 2500, which was brighter than the 16/44.1 masters that the records were cut from (the Zyx’s were darker than those masters). I also recorded the Goldring, and I had it at the same time as the Zyx's, so if the problem was digitizing or anything in my setup, the Goldring would also sound dark, and it was quite the contrary.

So, to respond to a new question: The seller is the official importer in my country, and the carts have serial numbers. We also looked at the Airy in a microscope before I took it home. The seller said he had looked at the first Fuji in a microscope before sending it to me as well (and he said it looked brand new).
And I don’t have any test records and can’t get a hold of any right now.

As for a "dark" sound, perhaps I just like it brighter than many other people, who prefer this treble dip, but these carts don’t sound like the vinyl-rips that I have downloaded, which all have the same sonic signature - not dark, but fairly neutral/accurate, but a bit colourized (but not much). And I don’t understand why my carts sound so different.
Fuji and Airy III are very old models, they have been discontinued many years ago, your distributor still have them. Grey market ZYX also have serial numbers, but the numbers are fake. I’m glad this is not the issue, but why don’t you just return your cartridges if they are so bad for your taste ?

For the price of ZYX, even if you paid 30% less, you can buy some amazing cartridges MM or MC. I don’t have my Airy III and premium 4D anymore, but i have more great cartridges and i don’t need that ZYX for another reason than yours, i think they are way too expensive, they have sealed body and aftermarket refurbishing is a pain in the ass, ZYX official exchange policy is not user friendly too (at least for normal people, who would not pay 80% of the brand new cartridge eachtime they need a retip after 2000 hrs of playtime).

However, could you answer one simple question:
Which cartridge do you like in your system ?

What was your favorite cartridge before your bad experience with those two old ZYX samples ?

If you need great vinyl-rips why don’t you use neutral MM cartridges loaded at 100k Ohm, something like Technics EPC-205c mk4, AT-ML170, Grace F14 LC-OFC with the most advanced styli/cabtilevers ? The best vintage MM loaded at 100k Ohm are equal or even better than very expenasive LOMC cartridges. Read more about it in this TAS article: http://www.regonaudio.com/Stanton881AudioTechnicaATML70.html
I read your post and came to the same conclusion that seems apparent to everyone.
Just an update: I've now returned the carts to the dealer. People are of course still welcome to download the clips and say if their Zyx carts sound the same as the ones I had on loan (it would be nice to have it cleared up).
"I read your post and came to the same conclusion that seems apparent to everyone."
That I just don't like these carts?
If so, then I concluded the same, but I'm still wondering why all the downloads then sound different, and why they all have the same sonic signature, since it would be strange if something had gone wrong in all those recordings + Zyx doesn't have a reputation of making dark sounding cartridges.
Do you always use this strange method to chose the cartridges ? 
It reminds me people who judge audio equimpent by youtube videos.

Cartridge in the actual system is not exactly what's on your digital recordings in the headphones. Maybe something wrong with your recordings, who knows, how could this be a reference?  Maybe you need a better headphones or better headphone amp, or it's about your hearing abilities or personal preferences and experience... or something else.  

Do you like digitaly remastered records? Maybe your LPs are not the best quality? Afterall everything depends on the LP first. The best souding LPs are mastered from the mastertapes or in real time with direct cut and this is where the magic begins!  Digitally recorded music must be better on digital source, i don't understand why people needs an LP cut from the digital master? 

If you had ZYX there in an article in the manual about analog reproduction. I'm sure the best way for you is to check your next cartridge in the actual system and not bother about all these perversion to make a digital copy of a digital master cut from vinyl to compare it to another digital copy made by someone else. 

I just don't get why not just play a perfect analog recording (with no digital in the chain of mastering process) with some nice cartridges in a good analog system with louspeakers (not headphones) in your actual listening room?     

But the more important is to compare new cartridge to some nice cartridge that you already know very well. Advantages or disadvantages must be obvious if you have no limits with phono stages/tonearm matching. 

Don't know any person who can say the ZYX cartridges are "Dark Sounding". 

Maybe you prefer digital to analog ? 
"Cartridge in the actual system is not exactly what's on your digital recordings in the headphones."

Yes, it is. Analogue to digital conversion is completely transparent within audibility. Although I use the Focusrite now, I've even run a long, cheap phono to mini-jack cable from the output of my CD player to the line-in on my old computer with a $50 soundcard, recorded a CD, then ripped the same CD on my CD-rom drive, adjusted the volume levels and done a blind test, but couldn't tell the recording apart from the original.
And similar tests have been done several times with the same results. Digitizing something doesn't change the sound of it.

And how many times do I have to repeat that my amp and speakers are in storage, so I can only listen through my headphones?!
To quote the late Christopher Hitchens: "It has made me think I could write a sequel called 'How some [audiophiles] apparently can't even read'".

And there's nothing wrong with my headphones. Even if there were, I could still hear the difference between my own recordings and the vinyl-rips, as I also stated earlier.

You don’t have to repeat that your system is away, but it is so strange and sounds like you’re looking for the cartridges for your CD rom.

Why do you need an expensive cartridge if you can’t hear the difference between your digital copy and true analog records ? Please find a nice original LP from the 70s or 80s mastered from the tapes, then buy a digitally remastered reissue of the same record pressed nowadays, then you can make your blind test, but with the vinyl. Then you can tell us what you like the most. Even at professional studios they can’t reach the quality of the original pressing if the original mastertape is missing or unavailable. But seems like you can, even with your cheap soundcard using CD-Rs. Now please tell me why a copy from the original pressing is not a good source for reissue, why people like Analogue Production always looking for an original mastertape to make a proper reissues? Why do they need super rare mastertape if they could just rip the original vinyl in mint condition for the reissue? According to your logic there is no difference between a digital copy and the original. This is the biggest mistake! Why musicians still using a mastertapes in the studios if the digital is much cheaper? Because this is analog and you can’t get same quality from digital. Why the best mastering engineers in the worls still use 100% analog mastering if they could simply convert everything in digital and use computers and waveforms on the screen? Becase this is analog and you loose something when it became digital. Doesn’t matter for you? OK, i think you will be happy with digital and it will save you a lot of money if you can’t hear the difference in your system or in your headphones.

Audiophile with a "system in the storage" should put the system in the listening room first and then look for a components for the system, but not vice-versa. You can’t chose a cartridge by youtube videos or vinyl rips.

I also use Sennheiser headphones, but the music in my system with full range drivers of 101db is another world, completely different experience when it comes to cartridges.

The prove of your wrong statement is that ZYX is not dark souding cartridge, it’s the opposite to the term "dark" or "warm". The bass and highs of ZYX are extended, plenty of details, great imagind and 3D soundstage, i know this for sure about the Airy III model. I’ve heard dark sounding cartridges, definitely not ZYX Airy III. As i said earlier, if you can't get the LOMC sounds right then it will be much easier to get MM sounds right. 
OK. So after listening to several different tracks that you made available for downloading I'll make a couple points.  First, Mastodon rules!!! Second, I think that the Airy and Fuji are sounding pretty close to the way they should.  This is not "dark" sounding to my ears compared to the CD rips.  It actually sounds a lot better to my ears than the CD. The ZYX cartridges have a house sound of "ultra-smooth", for the lack of a better term.  I hear this in your rips. So its not that they don't extend full frequency, but rather they don't emphasize the attack of the notes and they loose a bit of the dynamics you might like to have with rock music. I was focusing on the drum/cymbal sounds and guitar primarily. FWIW, ZYX cartridges truly shine in their 3D presentation and imaging and I don't think that one can appreciate this character as well in headphones.

I do think you would be able to coax out more dynamics and some attack by pairing them with the right tonearm and getting the VTA and VTF just right.  But, as @chakster has mentioned, you might have a better time with other LOMC (Lyra comes to mind) or a great vintage MM. 
The OP and all the responders, including me, are talking past each other. Typical of civil discourse in the age of the cell phone.
i feel sorry for all of us.
It’s too late to edit my post above, but, for example...
Chakster, The OP is not saying that the ZYX cartridges are dark sounding. He is asking WHY they sound dark to him, via his digital copies of LPs played through his headphones. He seems to recognize that something is "off", in order for the cartridges to sound as they do to his ears, in his set-up. The experience in his home system, such as it is, differs from his experience when he first auditioned the cartridges on some other rig. Or on his own rig but digitized by someone else. (I am not sure which.)

To anyone else, I don't see where the OP ever stated that "digital is better than analog". He is just telling us how he auditioned the two cartridges and that his method is constrained by the fact that part of his system is packed away.  I don't know whether he prefers digital to analog or vice-versa, just from reading his posts, except that he does say that he cannot distinguish any difference between his digital rips of LP content and signal derived direct from an LP, in his system.  There are many others who share that opinion, but most persons in that camp are digitizing with more expensive stuff, not to say better stuff.

To the OP, in all your ensuing responses, when you describe your listening experiences, were they ALL based on listening to digitized copies of one LP or another, regardless of all other variables? In other words, have you ever heard either cartridge directly via an all analog pathway?

Maybe the moral of the story is to simplify your question before posting.
Lew’s simplification comment is spot on.

One of the drawbacks of being so thorough is that the number of steps added to the process offers more opportunities to miss something.

I get that the OP is trying to be systematic and thorough, but going through (for example) multiple alignments is a waste of time in the context of what he’s trying to accomplish. When was the last time someone told you that Loefgren results in a deficient top end in comparison with Baerwaald or Stevenson?

Because of the number of steps and therefore, opportunities for errors to creep into the process (ask me how I know), I’ve stayed out of this conversation.

I’m waiting to hear back a year from now how the OP swapped out his highly capacitive tonearm cable for a lower capacitance one and this resolved the problem.

Sometimes, you can get too smart for your own good.

An example: a customer reported having one channel being much lower in level than the other. His conclusion was that I had miswired a step-up transformer. After a lengthy interrogation, I learned quite by accident that he was loading the channels differently - with one channel on his ZYX Universe seeing a 2 ohm load and the other one a load in the 30’s. When I asked him about this, he commented: "Well of course! One side of my room is "brighter" than the other ... words to that effect).

Folks do the darndest things.

The fact that the OP doesn’t hear any differences in a wide range of tracking force sets off a BIG alarm with me. It tells me that there’s something in his signal chain that needs addressing and it’s masking any other parameter changes he’s experimenting with.

A .02 to .03 gram change in tracking can make a huge difference in the dynamic presentation with these cartridges. My experience mirrors that of Salvatore. With the ZYX suspension, I’d start off in the 1.85 to 1.88 range.

Similarly, a heavy hand with too much anti-skate can kill dynamics. I’d set anti-skate to zero and add a tiny bit back over time, while being observant of the dynamic presentation.

I’d also play with mass tuning if the tonearm has multiple counterweights.

I realize that this conversation is about upper frequency response, but a compromised dynamic presentation can lend a perception of a lessened high frequency balance, since you’re killing the leading edge transients.

In short, this isn’t the sort of thing you can solve at a keyboard or by ripping files.

Thom @ Galibier Design
Well said @thom_mackris .
I admit that I should probably have shortened my original post to avoid confusion, so here are some answers and responses to the on-topic comments (some of this will be repetition), but first a question for karl_desch:

I included rips of my own recordings of Mastodon (Fuji and Airy), but also of the downloaded vinyl-rip (Fuji), and the downloads are much brighter. To me, the downloads is what I would expect a Zyx to sound like. Are my own "dark" rips or the "bright" downloaded rips more accurate in your estimations, meaning if you have a Zyx cart yourself and the Mastodon record, does the record in your system sound closer to my "dark" rips or the "bright" downloaded rip?
And thanks for taking the time to listen to them :-).

* The "other rig" that Lewm mentions are hi-res digital vinyl-rips that I've downloaded of several albums recorded by various people. They all have the same sonic signature, whether it's a Fuji or an Airy, which is what is so confusing to me. It would make sense that a rip from one person might sound different than my recording, but they ALL sound different than my recordings, and they ALL have the SAME sonic signature despite different turntables, tonearms, phono preamps, cables, etc.

* I listened almost exclusively to my digital recordings, but I also brought the Airy to an acquaintance's place both to make recordings and listen to the cart in his system. He was the one with a Thorens deck, a Mørch tonearm and PSB speakers. It sounded the same at his place.
I then also have recordings of the Ultimate 100 from the shop, where they set it up on their equipment. That one was even darker, so perhaps I just don't like these Zyx'es after all and something had gone wrong in the rips I downloaded (although it strikes me as odd that all the downloads had the same sonic signature, even though they were done by different people with different equipment, but ...)
Again, the Goldring was much brighter than the Zyx, and on the Dire Straits tracks it was brighter than the CD, even though the record was cut from a digital 44.1 kHz master. 

* About Baerwald/Stevenson, then I actually went from Stevenson to Baerwald with my previous Rega Exact cart, since with Baerwald the sound was a bit brighter (the Exact has a treble dip). But with the Zyx it didn't change anything.

* I fiddled with tracking force and didn't hear a change with the Zyx'es. With the Goldring 2500 and my previous Rega Exact I could hear a difference when changing the tracking force, and although I wouldn't call the difference enormous I passed blind tests. With the Goldring I also loaded recordings of light and heavy tracking forces into CurveEQ in Audacity (this plug-in let's you see the difference in EQ between two recordings), and it mirrored what I had heard: That one VTF setting was brighter than the other (the curve showed a decrease in high frequencies and a light bass boost on one VTF setting compared to the other).

* With the Zyx I heard a small difference when raising the VTA 6 mm and also with the Goldring, but the difference was very small (but I passed a blind-test). The difference with the Goldring might have been greater than with the Zyx.

* I also tried setting the anti-skating to zero instead of 1.5-2.0, and I think I also tried intermediate settings. I could see a small difference in the channel balance in the recordings, but that was all.

* It is of course possible that the capacitance on the cables in my arm is the culprit (it's the standard Rega cables), but it's then strange that the Ultimate 100 in the shop, on their turntable, also sounded "dark", and so did my acquaintance's Thorens/Mørch combo.

* In any case, I've returned the carts as mentioned. It would of course be lovely if we could figure out if the explanation was not that I just didn't like the Zyx'es, since those rips that I downloaded were some of the only ones that I had truly liked. But don't worry to much about it, guys :-).
I'm considering Hana, Shelter or Soundsmith instead, but I'll look into it.
And then just to deal with the off-topic points being made:

I also use Sennheiser headphones, but the music in my system with full range drivers of 101db is another world, completely different experience when it comes to cartridges.

Obviously, I also hear a difference between my speakers and my headphones, but you're still missing the point. The point is that there is a DIFFERENCE between the vinyl-rips I downloaded and my own recordings, and anybody would be able to hear that difference on both speakers and headphones.

Now please tell me why a copy from the original pressing is not a good source for reissue, why people like Analogue Production always looking for an original mastertape to make a proper reissues? Why do they need super rare mastertape if they could just rip the original vinyl in mint condition for the reissue?

This is where you're contradicting your own point.
The vinyl edition of the album is not the source, and often it's not even close to the source. Yes, some vinyl pressings would be audibly indistinguishable from the analogue master tape in a blind-test (save for ticks and pops), but often the two can fairly easily be told apart. Obviously, you would need/prefer the original source to make a reissue, whether on vinyl or CD. If they could get their hands on the master tape, no serious company would release a reissue of an album, which is just a rip of a vinyl record, since the vinyl edition doesn't sound like the master tape.

this is analog and you loose something when it became digital.

Not true. If you understand how digital audio works, such as what the Nyquist theorem states (and how many times it's been proven by various, independent people), what bit depth really is (it's not resolution), how sample rates really work, and what loop-back tests prove, then you know that you don't lose anything within audibility when digitizing a signal. On top of that, pro-digital people, for instance Stanley Lipshitz, acknowledge that early converters were poor quality, but from around the time that CD's were introduced and onwards, digitized copies of analogue signals could not be distinguished from the source, except for certain very specific cases done with poor early converters. The only reports of an audible difference with decent equipment are sighted tests done by analogue fanboys. As of yet, there are no properly conducted blind-tests that show that people can distinguish between an analogue source and the digitized copy, or even just the analogue source with an A/D/A loop inserted. And I would be perfectly happy to back this up (my sources range from recent years all the way back to 1984).

That said, almost all the CDs I have heard from the 80s sound poor: Screechy, shrill, cold and thin. But that's because they were mastered that way - it's NOT the fault of the medium, except maybe in certain very specific cases in the 80s, since certain A/D converters were less than stellar (as Stanley Lipshitz accepted).
If you understand how digital audio works, such as what the Nyquist theorem states (and how many times it’s been proven by various, independent people), what bit depth really is (it’s not resolution), how sample rates really work, and what loop-back tests prove, then you know that you don’t lose anything within audibility when digitizing a signal.

What i know for sure is that Digital Copies from the original mastertape of all well known Jazz LPs from the 60s, 70s (for example) are available and stored by the labels or copyright owners, but no one would like to use them when it comes to a proper reissue of some brilliant albums. If you don’t loose anything when you make a digital copy from the analog mastertape then could you explain why all the best people in business prefers original mastertape which is much harder to get, more expensive etc ? Analogue Productions runs by Chad Kassem, these people looking for the best possible quality and that’s why they do work with original master tapes, even if the tape is 50 years old. Nobody needs that digital copy from the tape, only original tape. Watch videos with Bernie Grundman who does mastering for Analogue Productions. If they do remastering they are doing it 100% analog, no digital crap (but it is much easier to work with digital). So i don’t believe in the fairy tales about digital copies that somehow equal to the original mastertapes.

Yes, i don’t want to discuss files or judge cartridges by vinyl rips, nobody knows how it was recorded and what is the reason why some files are better than others. I can’t imagine that some samples of ZYX are different that another samples of the same model, quality control will not allow this. I hope you find out what was the problem when you will find your next cartridge, something that you really like, still no answer what is your favorite cartridge or several cartridges that you really like?

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You certainly have things all figured out.  Glad we could help you.  Hope you enjoy those blind test listening sessions!
You certainly have things all figured out. Glad we could help you. Hope you enjoy those blind test listening sessions!
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haha, two post removed by moderator, i'm too lazy to post more in this thread 
Why was my comment deleted? Was it due to a swear word, or was it due to the content (and if so, can you elaborate)?