ack's system - end of round 1

Yeah, I don't agree with them on the resolution claim either. The whole point of inviting Al over was to clearly demonstrate the loss of resolution with low-level sounds like subdued triangle hits and the effect on micro-dynamics. All of these were very easy to demonstrate, and for example, with one setting the triangles are gone, and another, they are there... can't be more black and white than that. I think Berkeley is downplaying the strict definition of resolution, and may not fully realize what one hears in a system that acts like a microscope on the sources.

The effects of a tonearm, and why I love ferrite beads

Today's segment is on the fairly meaningless cartridge reviews and forum comments, and the benefits of ferrite beads.

A cartridge is just part of a very large chain, and for the mechanical side of things, an arm can significantly affect the sound of a cartridge (OK, we all know that, but do you really understand to what degree?). That's why reviews and comments are meaningless to me: we may have some context, but there is no way for us to tell how all the mechanical parts interact with each other in someone else's system.

I started a thread a while ago about how I magnetically stabilized my VPI unipivot arm (one ring magnet and two opposing smaller cylindrical ones), to avoid its inherent wobble - it's linked upthread and there is a video plus magnet specifications. That tweak also afforded me wider macro-dynamics, and of course images stabilized and timbre improved tremendously. That's also to say that unstable unipivots just SUCK.

During the last six months, I have improved on the magnetic stabilization by using two stacked ring magnets of different thicknesses and outer diameters, against the original opposing ones for stability, as shown below. There are online calculators to graph the magnetic field of various magnet configuration, and I chose this particular configuration for good reasons. One is stronger opposing forces, but the more subtle one is apparently equally important: evidently, the bottom of this VPI arm is some sort of steel and slightly magnetic; by using this combination of stacked ring magnets, they can every-so-slightly attract the arm when it's lowered (see third picture), though that inevitably affects VTF (but I compensate with the counter-weight). However, the real end result is that the arm is also stabilized on the vertical plane, offsetting subtle vertical movements by the cartridge, as it tracks the depths of the LP. Because of where the ring magnets are positioned in relation to the overall arm length, varying LP thicknesses have no measurable or audible effect, and the vertical stabilization is still as effective.

In conjunction with the use of ferrite beads (remaining pictures), here's the real sonic result: I don't recognize my analog. It is so alive, extremely resolving, dynamic, with presence, deep and tight bass, three-dimensional, with excellent micro-dynamics, that I literally do not recognize it. New sounds are popping left and right. I can easily hear pre-echo with many LPs, including D2D like For Duke and many Sheffield (apparently, there is a delay in the cutting process even for D2D), Telarcs, RRs, etc. I had some local folks over about 6 months ago, and the sound was plenty dynamic and resolving. This is now at a much higher level; the performance increase is just staggering, and I am re-discovering my collection.

Bottom line: a) as we all know, a great cartridge needs a great arm; b) the Pass XP-25 is susceptible to noise picked up by the cables, but in the end, as modified, a great phono stage; c) the tonearm cable sticking out no longer affects VTF as the arm moves across the LP

With respect to ferrite beads, I now have them everywhere, and their effect was only positive. Most folks don't care for them, so the only thing I will say to them is this: you have no idea; and they've had the most effect on my analog.

The stacked ring magnets, plus the opposing ones (and a ferrite bead on the tonearm cable):




Arm lowered, side view:


Ferrite beads on the phono cable and out the Pass XP-25:




Cheers

Easy. Extra HF shielding and mumetal over the MIT network box. If you were to look behind my rack, you would puke

Thanks Peter. I have no interest in spending money on racks, although surely there are much more stable ones; but this one does not sway unless agitated quite a bit. The fact it's been standing for 20 years or so is proof enough that it's adequately stable and I like the looks. If I were to do something, I would build one like yours, which is super stable. However, functionally, I am not sure there is a difference; the real benefit is in the shelves, but I am not going to spend thousands of dollars on shelves. The turntable, which is the more critical component, has its own custom shelf and isolation, as you know. Long ago, I tried an HRS isolation platform specific to turntables (two plates that intend to isolate the motor from the rest) and it was effective, but then I built my own isolation for the motor, which is also as effective and proven so with a stethoscope. Therefore, no real interest in expensive and uber racks, nor is it practical to try different racks. I do like reading the various relevant patents, but at the same time, the materials I use are proven in other industries as well, like aerospace (talking about the EAR Isodamp material, also found in the Magico QPods; and sorbothane). If there re going to be new ground-breaking isolation solutions, I bet they are going to show up in other industries first, like all known ones now have.

Folsom said:

I might.

Click to expand...

I think you would. However, the improvements in my analog over the last year or so have been fascinating, and let me give you some concrete data:

• The input gain on my Revox has been fixed for years - I record the BSO live from FM broadcasts - and what I clearly see now in the VU meters when I play LPs is roughly 3dB higher average VU gain, but most importantly, its overmodulation LEDs constantly light up, due to the explosive dynamic headroom. The cartridge has not changed, the XP-25's gain has not changed, the loading has not changed, the tracking force has not changed, the cables have not changed, the turntable has not changed; what has changed is in recent months is going from XLR-out to RCA-out on the phono (that's responsible for the 3dB VU gain), and most recently, the final version of the arm stabilization and the addition of the ferrite beads - the latter two have been responsible for most of the improvements
• I have gone to extremes to contain hum, and the results are black and white and quite easy to A/B:
  1. with max preamp gain, the MIT network box on the phono cable as is picks up hum, and about -10dB less of it with mumetal around it (measured head on, on the woofers)
  2. with max preamp gain again, the Pass power supply picks up a small amount of hum from the power line, and significantly less so when I put an MIT Z-Trap in series with the power cord - go figure. Lifting its ground actually makes things worse
  3. I have wrapped the entire XP-25 amplification unit with mumetal and copper shield (video shared years ago), and the decrease in hum pick up is roughly -10dB - a staggering number. The source of the hum here, as it turns out, was actually my DAC's power supply, so that has been moved off the shelf for further improvements
• The effects of the copper shielding are not easily measurable, but they are audible

As I go through my LP collection now, I can't help but be wowed from what I hear in terms of macro and micro dynamics, low-end authority and body (currently, Respighi's Pines Of Rome on RR is on the 'table), and new sounds are coming out, never heard before. Earlier today, I played Ramirez's Missa Criolla with Carreras, and the charango & guitar are so clear, you feel the air coming out of the siku, the reco reco is so woody, and I now have all the body of the bombos that I've always been missing before. I am not exaggerating when I say I don't recognize my analog, and the improvements are on a very large scale and easily quantifiable.

Cheers

PS: Speaking of the Respighi, the finale of the Pines Of The Appian Way is hold-your-cojones exciting and authoritative

Folsom said:

I'll try ferrite beads again, last time it was awful, but I had different cables.

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The important thing about ferrite beads is their operating range, thus, they must not be chosen randomly. For details, see http://www.analog.com/en/analog-dialogue/articles/ferrite-beads-demystified.html

I chose mine with an operating range over 1MHz, in order to absorb noise that would: a) otherwise affect the peak resonance of the phono stage/cable/cartridge combination, which is typically roughly in 1-2 MHz range (there is a thread on WBF on this, named something like 'Cartridge loading is a misnomer' - http://www.whatsbestforum.com/showthread.php?15077-Cartridge-Loading-A-Misnomer); and b) affect the Spectral devices, which operate well above 1 MHz.

Folsom said:

It's weird you have so much hum to start with. The cables are not shielded? I too prefer single ended, typically. Still, hum is one of the first things to go, usually.

Generally hum is the result of an engineering problem, but that isn't the case with unshielded cables.

Your DAC might benefit from a Schurter DENO.

Click to expand...

This type of hum is clearly picked up by the XP-25 phono stage and the MIT network box. The DAC's power supply emits a huge magnetic field around its transformers cores, measured with a magnetometer once I realized what is going on, and the XP-25 and MIT box pick it all up - it's not the cables per se, as in the 'wire'. The problem is that both the XP-25 and the MIT network box are stupidly enclosed in aluminum, as opposed to say steel, and they are susceptible to hum pick up - hence the mu metal. If you search the net, there are many others that either place their XP-25 far far away from anything else, or use steel plates above and underneath it for hum shield. The MIT box has a screw that is to be connected to ground, and it works to a certain degree, but it's with the mu metal that things really quiet down. I suspect its shield is not entirely effective because of the cutout/opening with those impedance and articulation control knobs, and noise seeps in from there. So my network box is literally buried in mu metal all around.

By contrast, the Spectral transport's three transformers sitting further higher from the XP-25 emit extremely low magnetic hum, and the FM tuner's own transformer really nothing, therefore, it sits comfortably literally on top of the XP-25 with no problems. I had none of these problems with my previous phono, an Ayre P5xe, and other non-networked cables and an otherwise identical layout.

As another example, the arm itself can pick up hum, and therefore all arms are grounded. This is easily demonstrable with my unipivot, by simply lifting the armwand off the pivot point, at which point it loses its ground connection and a fair amount of hum can be heard. Similarly, hiss goes sky high if you unplug the armwand entirely, because the circuit is now wide open.

So yes, hum, like any other type of noise, is an engineering issue, fairly complex, and not always the result of ground loops.

Sorry, I don't mean to lecture you, just point out some things for the wider audience reading all this - I am sure you are well versed in all of this. Depending on the system and its resolution, a bead may or may not do anything, and can be detrimental if they are the wrong type. I heard no improvement back in the day with the Ayre phono, but then again, its resolution is nowhere hear the XP-25's. In the current case, the smoothing of the highs especially with cymbals is quite noticeable, and they take on a very metallic tone, as they ought to. I got similar results with the FM tuner, as reported earlier.

Impedance-matched cables?

I've been meaning to write about this for a long time, and it's about those cables that claim to impedance-match interconnecting components. Well, let's ignore for a moment that equipment from the same manufacturer are already impedance-matched, and entertain the general idea.

My MIT networked cables have a switch for that (low/medium/hi impedance) and it's because of the complexity of their networks, which behave like a separate component in between the interconnecting components. But then, we have those other, competitor networked cables with a simple inductor to attenuate the high frequencies ("smooth the highs" as the manufacturer claims), and which presumably need to be sent back to the manufacturer to have their impedance adjusted every time we switch equipment, and for which people spend thousands of dollars on these networked cables. FWIW, I had such a phono cable "custom-made" for my A90/XP-25 and it sounded like you can guess, colored, to put it mildly.

I'll quote the following from this MIT paper http://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf

However, impedance matching or termination is required for video and RF cables because the signals have much shorter wavelengths! As a general rule, cables begin to exhibit “transmission line” effects when their physical length is 10% or more of a wavelength at the highest signa lfrequency. This occurs with video cables over a few feet long and with CATV cables over a few inches long. To avoid reflections of energy from one end of the cable to the other, the driving source and receiving load impedances at each physical end of the cable must match the cable’s characteristic impedance. Such reflections will cause visible “ghosts” or “rings” in video images. For AUDIO cables, termination is NOT necessary unless cables are over about 4,000 feet long!

Click to expand...

Here's the issue: someone please show to me that a simple inductor in between components requires impedance adjustment, at audio frequencies.

Yes, and a low value, so that the corner frequency is in the high kHz

A daring tweak

Vinyl is so incredibly complex and frustrating, but also very rewarding. The picture below shows a very thin layer of sorbothane in the shape of a T placed between the cartridge and the headshell. The results are immediately noticeable as further clarity and articulation in the highs, with noticeably less edginess. A simple tap on the headshell with a metal object results in a duller thump, with less high frequency content and ringing. The screws already use plastic washers. The real problem with this presumably easy tweak was re-aligning the cartridge - what a pain. I have not noticed any drop in dynamics or bass performance, and VTF was only affected by 0.1g, easily compensated.

PeterA said:

Interesting. Congratulations on your continued quest via tweaking to improve your sound. Why do you think that decoupling the headshell from the arm tube causes such an improvement in sound quality? Are vibrations from the cartridge now not traveling through the arm tube to the uni-pivot bearing or are vibrations in the arm tube now not hitting the cartridge?

Click to expand...

The A90 appears to want to operate isolated, so I am building on top of its isolation design, which is two-fold: a) the contact area with the headshell is deliberately small (just two very narrow perpendicular lines, forming a T); and b) the built-in damping system, described best in its manual:

WRD system

Adding to the list of important components is Ortofon’s patented Wide Range Damping (WRD) system. In this system, a small, heavy platinum disc is sandwiched between two rubber absorbers, both with different properties. This ensures not only an exceptional tracking performance, but also create a perfect damping through the entire frequency spectrum. Because of this, distortion and resonance are virtually eliminated entirely

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Although the cartridge/headshell contact area is now larger, the sorbothane damping appears to absorb ringing by the metallic arm. The decrease in high frequency distortion is quite noticeable if you are coming from years of playing records one way, and the increase in articulation even with very quiet passages is also quite apparent - I was playing Carmina Burana on Telarc, and the subtle triangles during soft chorus singing were quite distinct and complete, which was not the case before).

PeterA said:

I would think that this tweak would not be as effective on my SME arm because the headshell and arm are designed to take all vibrations from the cartridge away from the stylus and to the gimbal bearing and massive armboard. Your report offers an alternative take to what I have always read as a desire to have a very rigid cartridge/headshell interface. Doesn't the A90 have three small mounds on its top face for better direct coupling to the headshell?

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Yes, it's unclear how well this tweak would work in other systems. What is clear yet again is how important the arm is to an analog system.