adnick
Addicted Member
Like many I’ve enjoyed reading the Korf blog and find their new headshell and tonearm intriguing.
Each can be found here (no affiliation). http://korfaudio.com/#popup:timed
Thought this was a very interesting reply to questions about the new Korf tonearm that were asked over at Lencoheaven, many points made should generate lively discussion.
“Hello gentlemen,
I'm here to try and answer your questions about all things Korf. Please understand I can't do that daily, but I will be popping in every couple of weeks or so. I've been on Lencoheaven for more than a decade. It was and is an amazing source of information and support. Great to "see some familiar faces" too!
To summarize what has been asked so far:
1) Flexure pivots. Yes, they are kind of like 2 crossed leaf springs. They are made by precision etching and electron beam welding in such a way that the center of the pivot doesn't move when its outer sleeve rotates. The pivots are indeed eye-wateringly expensive, and there's virtually no price break if you order more of them. But once you experience a tonearm that uses flexure pivots, it's hard to go back.
To counter the flexure's tendency to self-center, we use the bearing in a "quasi zero stiffness" (QZS) configuration. It works a bit like "negative K" lab isolation platforms.
For the vertical axis, we use hybrid ceramic rolling bearings. The starting torque is less critical in "yaw". We did build a prototype with a vertical flexure and then a dampened rolling bearing to integrate the movement (kind of like the Naim Aro). The sonic benefit achieved was not commensurate with the extra expense.
2) Why do we use Stevenson and not the supposedly more "advanced" alignment?
We chose the simplest alignment because it does not matter that much. If anyone thinks that longer tonearms or linear trackers sound better because of lower tracking error—make an easy experiment. Mount the cartridge in your linear tracker 2 degrees askew. Or move it forward 5mm. Come on, be bold. Introduce a large permanent tracking error. Will this make a linear tracker sound like a 9" pivoting arm? Will it introduce IGD?
To get even a hint of measureable distortion, the planar alignment has to be way off. 15-20 mm or so. People obsess over planar alignment because it's an easy change that gives an illusion of control. In reality, things like torsional forces on the cantilever, bearing stickiness or arm tube resonances matter orders of magnitude more. And I'm not even mentioning the cartridge assembly errors.
3) Why are the Korf tonearms so heavy?
It turned out, our tonearms aren't heavy enough! We had to produce an extra headshell weight for the stiffer MCs and modern DS (optical) cartridges. These sound best with an extra 6g on the headshell.
As you probably know, we did quite a large study of low frequency arm behaviour (https://korfaudio.com/blog67 and onwards). Our decisions regarding the moving mass are informed by the results of this study, and by our research into bearings. As a result, our tonearm works great with most moving coil and moving magnet (MI, fluxvalve etc) cartridges, no matter how high the compliance. I personally daily use the TA-SF9R+HS-A02 headshell with Shure V15V/JICO SAS and Grace F-9 (Soundsmith stylus). There are no problems, and the woofers on my JBL Array 1400s are dead still (unless the music calls for them to move!)
There's another side to this question: for many modern tonearms, the published effective mass number has no basis in reality. One manufacturer insisted it's 14 gram. When somebody pointed out their headshell weighs 14 gram, they quickly changed it to "above 30 gram"
“
Each can be found here (no affiliation). http://korfaudio.com/#popup:timed
Thought this was a very interesting reply to questions about the new Korf tonearm that were asked over at Lencoheaven, many points made should generate lively discussion.
“Hello gentlemen,
I'm here to try and answer your questions about all things Korf. Please understand I can't do that daily, but I will be popping in every couple of weeks or so. I've been on Lencoheaven for more than a decade. It was and is an amazing source of information and support. Great to "see some familiar faces" too!
To summarize what has been asked so far:
1) Flexure pivots. Yes, they are kind of like 2 crossed leaf springs. They are made by precision etching and electron beam welding in such a way that the center of the pivot doesn't move when its outer sleeve rotates. The pivots are indeed eye-wateringly expensive, and there's virtually no price break if you order more of them. But once you experience a tonearm that uses flexure pivots, it's hard to go back.
To counter the flexure's tendency to self-center, we use the bearing in a "quasi zero stiffness" (QZS) configuration. It works a bit like "negative K" lab isolation platforms.
For the vertical axis, we use hybrid ceramic rolling bearings. The starting torque is less critical in "yaw". We did build a prototype with a vertical flexure and then a dampened rolling bearing to integrate the movement (kind of like the Naim Aro). The sonic benefit achieved was not commensurate with the extra expense.
2) Why do we use Stevenson and not the supposedly more "advanced" alignment?
We chose the simplest alignment because it does not matter that much. If anyone thinks that longer tonearms or linear trackers sound better because of lower tracking error—make an easy experiment. Mount the cartridge in your linear tracker 2 degrees askew. Or move it forward 5mm. Come on, be bold. Introduce a large permanent tracking error. Will this make a linear tracker sound like a 9" pivoting arm? Will it introduce IGD?
To get even a hint of measureable distortion, the planar alignment has to be way off. 15-20 mm or so. People obsess over planar alignment because it's an easy change that gives an illusion of control. In reality, things like torsional forces on the cantilever, bearing stickiness or arm tube resonances matter orders of magnitude more. And I'm not even mentioning the cartridge assembly errors.
3) Why are the Korf tonearms so heavy?
It turned out, our tonearms aren't heavy enough! We had to produce an extra headshell weight for the stiffer MCs and modern DS (optical) cartridges. These sound best with an extra 6g on the headshell.
As you probably know, we did quite a large study of low frequency arm behaviour (https://korfaudio.com/blog67 and onwards). Our decisions regarding the moving mass are informed by the results of this study, and by our research into bearings. As a result, our tonearm works great with most moving coil and moving magnet (MI, fluxvalve etc) cartridges, no matter how high the compliance. I personally daily use the TA-SF9R+HS-A02 headshell with Shure V15V/JICO SAS and Grace F-9 (Soundsmith stylus). There are no problems, and the woofers on my JBL Array 1400s are dead still (unless the music calls for them to move!)
There's another side to this question: for many modern tonearms, the published effective mass number has no basis in reality. One manufacturer insisted it's 14 gram. When somebody pointed out their headshell weighs 14 gram, they quickly changed it to "above 30 gram"
