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Tonearm microphonics

When I have the volume at my normal level & tap the arm (not whilst playing vinyl) it is slightly amplified... Is it possible to significantly reduce/eliminate this?

Current set up - Roksan Xerxes 20plus, Origin Live Encounter tonearm (thin cork ring at the base) with Lyra Skala.

Apologies if this is a stupid question!
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atmasphere's avatar
atmasphere
11,604 posts
 
@bdp24 
Can an arm be "too" damped, too non-resonant? Are those two things the same?
Not really.

Removing resonance from the arm tube is a good thing and its impossible to overdamp the arm tube in this regard. One **massive** problem with that though: messing with the mechanical resonance caused by the compliance of the cantilever and the cartridge/arm mass is not good, unless by doing so you get it inside the 7-12Hz window. So if you are applying damping materials to the arm, you can mess that up and with dreadful results.

Damping can be done by a damping trough too; which is an entirely different form of damping, but IME that can lead to problems especially if the LP is not perfectly flat. Generally speaking the arm will not need this kind of damping if the mechanical resonance is in the right window.

So you have to be careful when bandying these terms about. They can mean three or four different things depending on who you're talking to and that's on a good day!
larryi
3,722 posts
 

bdp24,

Yes, I do think it is possible to overdo damping.  Specifically with tonearms, I have experimented with the damping fluid level in my Basis Vector arm and heard the difference with the fluid level in the damping trough of an SME arm.  Too much damping results in a lifeless sound. 

I think tuning of resonance and damping of vibrations in all parts of the reproduction chain is NOT a matter of trying to minimize vibration to the utmost.  I was in attendance when a representative from Symposium tried different shelves under a CD player.  The very top model that Symposium offered, that does the most to dissipate vibrations as heat, actually sounded quite bad--dry and thin.  The representative agreed with this assessment; there can be too much damping.

I've heard the same with devices for placing under speakers, exotic racks, etc.  I spoke with someone in the high end industry that has heard hundreds of different systems.  He said that he has NEVER liked the sound of a system employing exotic and extremely expensive vibration damping rack/shelves.

moonglum
619 posts
 
Atmasphere is right to point out that there are adverse side effects where the geometry of the disc is not uniform and flat when external damping in the form of silicon goop is applied.
Not only does it damp resonance but it also exerts drag on the arm's movements not unlike extra friction in the bearing. this means if the arm has to weave from side to side or follow vertical undulations there will be slower reaction.

However, here's the kicker : even if the disc was drilled perfectly centrally and was perfectly flat there would still be a problem because the tone arm must "sign" across the disc as it still must follow the inward "spiral" of the groove to its centre.

Therefore Stringreen's suggestion was extremely sensible i.e. if the arm seems naturally well enough damped, try to run it without damping fluid.
bdp24's avatar
bdp24
9,452 posts
 

In his original review of the Well Tempered arm, and in Bill Firebaugh’s literature on his arm, Gordon Holt discussed the viscosity of the arm’s "bearing" well damping fluid, and how it allows the arm to freely move at very low frequencies (those of the arm following the groove, warps, etc.), but keeps the arm’s bearing rigid above those frequencies, such that it allows it to act as a normal mechanical bearing, but with very low friction, and no bearing rattling or chatter

The Townshend Rock turntables damping trough behaves in the same manner; warps are "slow" enough to not impede the movement of the arm in response to them (up and down), and the same with groove eccentricity (left and right). Those frequencies are very low, far below the lowest contained in recordings. At audio frequencies, the viscosity of the damping fluid in the trough is heavy enough to "lock" the front of the arm in place, just as an arm’s bearings do at the arm’s rear. The result is the tightest, cleanest bass I’ve ever heard from LP’s. LP surface noise is diminished as well, and violins take on a smooth sheen, their timbre sounding organic, not electronic, bright, or etched. The resonance-reducing capability of the Rock system also increases the audibility of inner detail (listen to one of the great recordings of the large choral groups Robert Fulton made---every voice is individually audible, or the massed string section of a symphony orchestra) , and micro-dynamics. With the low-level "haze" (that created by uncontrolled resonances in the playback machine) removed from the sound of LP’s, the sound IS more like that from master tapes, the mechanical nature of LP reproduction reduced. Does this sound like a commercial ;-) ?

One interesting thing discovered with The Rock is that it decreases the difference in the sound of arms mounted on it, the damping apparently compensating for the less well-damped nature of cheaper arms.

bdp24's avatar
bdp24
9,452 posts
 
To clarify, the relationship between warp and eccentricity demands on the ability of the arm to follow them, and the frequencies involved in those demands, are a matter of the time it takes the arm's headshell to traverse a warp or eccentricity. If a warp takes the arm's headshell a full second to travel up and then back down, the frequency involved is 1Hz. The same for an eccentricity that it takes the headshell a second to follow left and then right, back to where it started; one second equals 1Hz. If the warp or eccentricity take 0.5 seconds to traverse, the frequency is 2Hz, and so on.
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