Hi Frogman and Ct0517, I have been running in a NOS 420STR for just a few hours and am similarly impressed. Amazing performance from what could be mistaken as a missing gray plastic piece from a Revel model. |
Listening to the M420 last night put a smile on my face while reading Mike Fremer's comparison of the $9K H&S Ice Blue to Ortofon A90 and Lyra Atlas. I felt no more than a slight tingle of penis envy for these MCs.
It's interesting how much smaller Acutex's tri-pole induced magnet assembly is in the 420 series as compared to the prior 320 series. The 320 marketing literature talks about the advantage of oversized magnets. Accordingly the 320 has a much larger and heavier 6.2gm 320 body. The cantilever armature of the 320 is also more complicated, with tabs that project radially to the induction poles inside the cartridge body. In contrast the 420 is a svelte 4gm. The 420 looks cheaply build in comparison to the 320. But maybe looks are deceiving. Unfortunately one of the armature tabs on my 320 is bent and in need of repair, so a comparison will have to wait. |
It might be useful to agree on a few tracks that reveal stubborn sibilance problems-- perhaps a female voice. These can be revealing of subtle problems in all but the most optimal phono set-ups. I'll ponder which albums may be helpful. |
Funny, Acman3: with the same cartridge and tonearm I have been cycling through the entire Who catalog. The 420's tremendous sock, clarity, and separation play well with the power trio's delineated guitar, bass, and drum lines. |
Slaw, to resolve the clearance problem with M420 I added a graphite shim. In the past I've fabricated shims from hardwood for this purpose. I can't imagine why Acutex made this cartridge body so short with angled pins. |
Frogman/Dover, I wonder if this is about adding a small and constant skating force to help propel the carriage toward the spindle in a more controlled manner. Similarly, when leveling the carriage, optimal set-up may call for a very slight tilt of the manifold toward the spindle to gain assistance from gravity. I tend to find level empirically-- by watching the behavior of the stylus in the lead-in and run-out sections, observing cantilever deflection, and listening for tracking problems and distortion. I suppose I should add a leveling bubble to the air manifold for a more precise assessment. |
Slaw, That's a good idea. A bond between similar materials couldn't hurt. |
Frogman, I have been thinking of trying that AN tonearm wire. Do you use it in a long uninterrupted run from cartridge to phono stage, or in a short run to a connector block on the tonearm? The AN wire is lighter gauge than the screened silver wire that I currently use from cartridge to phono stage. In a four-wire balanced arrangement this screened silver wire has excellent noise rejection, but must be dressed very carefully(perhaps impossibly so) to avoid interference with free movement of the arm wand. This wire has 4 ohm resistance over a 160 cm span. Any idea what resistance the AN wire presents per foot or meter? |
Thanks, Frogman, I'll give it a try. I only asked for its resistance over length to get a general sense of whether such fine filament wire makes sense for a long run. Obviously typical phono applications enlist tonearm wire for the short run from cartridge to RCA or XLR connector block. |
Slaw, IME on Trans-Fi linear tonearm the M420 STR's sibilance gradually resolves over 50-75 hrs. What little remains of it thereafter is an acceptable compromise, considering the eyes-wide-open performance that communicates everything that's great about vinyl. |
Ct0517, on my TransFi the "loom problem" is compounded by slightly thicker discretely shielded wires, and by the extra wires required for a balanced circuit. The feather-lite short wand is particularly vulnerable to fouling.
http://cgim.audiogon.com/i/vs/i/f/1284313864.jpg
The gantry grommet is about half way across the LP. The loom is dressed like an egg-beater. It expands and contracts as it moves, with the force vectors of the discrete wires approximately cancelling. |
Nandric, Absent direct experience with Terminator, your remark would seem to be a good example of what psychologists call the false consensus effect. |
Dover, can you clarify a few points concerning the effective horizontal mass of ET? The manual states that it is 25-35gms. Is this the mass of the wand plus manifold tube, which is then increased by addition of up to 40gms in counterweights?
I understand that the mass of hanging decoupled counterweights behaves differently than fixed counterweights. It would be interesting to have the math on this horizontal pendulum effect. In any case, while the design may lower horizontal inertia to an extent, it will also contribute to horizontal inertia to an extent. I would imagine that the effective horizontal mass of the entire moving system is quite a bit higher than 35gm.
In the course of developing the predecessor of the Trans-Fi tonearm, Poul Ladegaard experimented with a pendulum counterweight. For whatever reason that feature was abandoned.
BTW, with a custom lightened CF slider and wand the horizontal mass of my Terminator totals 35gm. This includes custom front and rear wand counterweights designed to vary the wand's vertical effective mass. On my full-range system with a sub to 18Hz, the lighter horizontal assembly sounds better than the heavy one. Also, variations in vertical effective mass are more impactful than relatively large variations in horizontal mass.
Lots of variables. |
Ct0517, At CES Franc K. mentioned a horizontal mass of around 100gm for Airline. He said that this worries some pivot arm guys, though in practice is "no big deal" w/r to LF performance. The Airline interests me as well-- incredible fit n' finish. I've read that one of its key advantages is very tight bearing clearance. At the high pressure necessary to float a "hard" captured air bearing of small surface area, this implies a low rate of airflow and thus relatively low turbulence and vibration.
Terminator can be mounted on pretty much any turnable. Porting the arm across turntables requires pedestals of varying heights to match the varying distance from a particular arm board to the top of the turntable mat. The pedestal can be ordered with an off-set stud mount that spins to accomodate any existing armboard hole vacated by any pivot arm. I made a DIY brass pedestal with this feature. |
To clarify, I mean to say that at LOW pressures approaching the threshold of mistracking, the bass comes up and musical presence improves. |
Hello Ct0517 & Dover, of course no offense taken. The discussions about the significance of variations in horizontal mass have been of interest here and in several AA and DIY forum threads. I have yet to try a really low-compliance cartridge on Trans-Fi-- which may change my current opinion that "less is more" w/r to horizontal mass. I've experienced this with a large number-high compliance MM/MI cartridges and a small samples of medium-compliance MCs.
I'd have to dig for the URL, but I recall that either Mark Kelly or Poul Ladergaard calculated the lateral stylus force applied by a linear tonearm as compared to force attributable to overhang and off-set in a conventional pivot arm. If as modeled, the lateral forces of a pivot arm(to which we must also add the tonearm's effective mass) are significantly greater than that of a 100gm linear arm, then this may suggest that a linear arm(whether 35gm or 100gm) cannot be faulted for its large lateral mass. Perhaps this is what F. Kuzma meant when he said that 100gm is "no big deal." In any case, I was not suggesting the relative superiority of any of the three very different linear arms under consideration. |
ct0517 wrote: " Does the wiring on the Terminator play a role in damping (stabilizing) the stylus?"
It may do so, but not by design. If not carefully dressed between the gantry and the wand, the tonearm wires have the greater potential to do harm by fouling the wand's free movement. The torque effect is exacerbated with a five-wire balanced harness. To minimize torqueing, one of these days soon I'm going to try making a harness with very light-gauge AN silver wire. |
Air escaping from the bearing can cause subtler damage by modulating the arm wand and stylus. This may be a necessary evil in any air bearing design... Doubtless the effect can be mitigated by reducing air gap tolerance or with arm wand damping. I suspect that the Kumza Airline has a particularly close gap, as it is designed for higher pressure 60 psi operation. At CES I asked F. Kumza about this. He replied that as the technology is well proven in industrial instruments in microscopic applications, it should be good enough for audio.
Trans-Fi/Ladegaard is the only air tonearm that I know of that doesn't use a captured air bearing. Air escapes freely all around the bearing. With this design the lowest possible air pressure that floats the bearing(about 1 psi)sounds best. A different approach. |
Chris, the manufacturer recommends lowering air pressure of Trans-Fi to the point that the needle skips backward a groove, then slightly increase pressure to restore tracking. The air pressure at this threshold depends on the weight of the selected wand and counterweights. One owner with a very light wand and counterweight set-up reports running below .25 psi. I'm currently using a heavier custom wand with dual front and rear counterweights and a CF sled that together "float" at around 1.25 psi.
Similar to what I gather is the case for ET, with the stylus resting on a stationary record, a rumbling through the speakers increases slightly with rising air pressure. This effect is never at a detectable level with music playing. However, at pressures approaching the threshold of mistracking the bass comes up and musical presence improves. |
I would think that the favorable qualities of a captured air bearing in this application are maximum bearing stiffness(a function of air pressure) and minimal air turbulence(a function of air velocity through the bearing and surface friction.) The best one should have the tightest clearance in order to minimize air loss and turbulence attendant with velocity.
In contrast, the stability of the Trans-Fi bearing is not a function of stiffness, but rather of aerodynamic balance. It functions like a glider wing that requires only the minimal air pressure and flow to obtain lift. It operates in a horizontal plane, rather than in 360 degrees as with a captured air bearing. The air velocity through the bearing is higher than with captured air bearing, but as air pressure is low, turbulence is minimized. In this particular instance, the more pressure, the higher the lift, the sloppier the bearing. |
Chris, Trans-Fi needs only a 4 psi aquarium pump, smoothing tank(s), and a good brass needle regulator. No need for an evaporator tank, given the small 2-3 psi differential between the pump and the tonearm. One may be tempted to think of it as a poor man's solution, however in my view its design has fewer problems to solve than a captured air bearing and illustrates the virtue of KISS. |
Hello Harold, I hope some day to compare an ET to my Trans-Fi-- maybe when I find space to set up the VPI TNT and Kenwood L-07D side by side. Squeezing two linear arms onto one turntable wouldn't leave space for an LP... |
