Fine Tunes #13
If you read last month's "Fine Tunes," perhaps you've already checked that your equipment is set up at an acoustically null point, avoiding resonances induced by the speakers and their interaction with the room. That applies to audio racks as well as "incidental shelving," heaven forbid. Phono cartridges, phono stages, and tubed preamps are most prone to these microphonic effects. If you pop the top of your preamp and scream directly at that costly New Old Stock tubeset while the gain is up, you'll hear your voice from the speakers! Even a damped, shielded phono cable reacts to vibration and resonance.
As a result, many resonance-control products attempt to decouple the component from the shaky, gettin'-jiggy-wid-it world we live in. During the day especially---and even now, late on a Saturday night---I'm stunned by the way my monitor occasionally rocks on its pedestal in small, hectic cycles from the rumbling street below.
None of this is good for your audio equipment. Whether from sound waves direct from your speakers, standing-wave "hot spots" in your room, or footfalls and truck rumbles, it's all bad.
Now let's turn the picture inside out. What do you think is happening inside those serenely glowing 6922s, 6SN7s, and what-have-you? Believe me, there's a whole lotta shakin' goin' on. Tap some of those much-sought-after NOS small-signal tubes with the gain up---gently, please---and most of them will tinkle, chatter, and roar like a cannonade. I'm not saying they can't sound wonderful, just that, when using them, one is best advised to consider some form of damping. This applies to power tubes as well (though to some more than others), and even to solid-state components, which can also be shown to react to vibration. The point is, all internally generated resonances---in everything from the capacitors to the circuit boards they sit on---ultimately affect the sound.
Consider the CD transport. Within the tray, the platter tries its best to reliably spin what is often an eccentric, wobbling disk while the laser mechanism gamely tries to keep up. The huge amount of physical effort this involves was driven home clearly when I peered into a YBA CD-1 Blue Laser whose top had been removed. Like a rubbernecker at a Cronenberg car crash, I watched in absorbed, horrified fascination as one particularly offending disc drove the tracking mechanism into a paroxysm of corrective motions. Remember, even small, light parts in the laser assembly have mass, and can induce resonant modes in nearby parts by their movements.
And turntables? Don't get me started.
In short, it's a resonant universe. Deal with it. You think you're sitting still as you read these words? Take it from me, bubbie, you're vibratin' like crazy.
What to do? One theory has it that creating a drain path with spikes or cones for internally generated resonances is the way to go. I agree, although it's fairly controversial---many deride the notion that footers of whatever shape can act as diodes, allowing an outbound path for resonances without allowing them back in again. What is incontrovertible, to my ears, is that coupling a component to the shelf it sits on often benefits the sound.
A trio of footers most often does the trick---three points define a plane. With some components, even the cones' relative positions can make a difference. When spiking a CD transport, for instance, you might consider placing one footer under or near the spindle, if possible. Setting them up directly beneath power transformers is another favored technique, as transformers can mechanically vibrate and hum, chattering away like magpies in a tree.
Now what, you're asking yourself, can you do to test these outlandish ideas without spending a fortune? I used to keep on hand several butcher blocks of maple---a very fine wood to use under front-end components and amplifiers, if the amps aren't too enormous. These blocks are relatively easy to come by and can be had for something under $40 or so. If you must, oak isn't terrible, but it doesn't sound as good as maple, for whatever reason. Butcher blocks are dense and weighty, which helps decouple the component, especially if spikes or cones are used.
You don't actually have to use footers; just getting your components up on the block should help. But I strongly recommend footers, and DH Labs and PolyCrystal cones are relatively cheap and very effective. The original Mod Squad Tiptoes are still available, as are a number of more costly footers. The best thing is simply to try it and hear for yourself what happens. Use your ears, m'dears---you'll be surprised.
Another cost-effective decoupling material is bubble-wrap. I know one audiophile and VTL enthusiast named Earnest, bless him, who swaths a good deal of his system in the bubbly stuff, and even uses it as a turntable platter mat. (He's built a fantastic system, by the way.) You can place your tubed or even solid-state preamplifier on a cushion of bubble-wrap---or your CD player, if you hear an improvement.
A slightly less elegant but inexpensive and effective way to decouple involves placing small inner tubes beneath front-end components. You can settle and level your CD player or preamp on one, with or without bubble-wrap, and see if that works for you. While the notion of improving the sound of audio components by placing air bladders under them has caused gales of derisive laughter from some quarters on rec.audio.opinion, I've heard it work wonders. From there, it's only a relatively short and, again, relatively inexpensive step to Bright Star's Air Mass products, which I also highly recommend. I use an Air Mass 2 with a Big Rock sandbox under the SpJ/La Luce turntable to excellent effect.
Next month: More vibratory investigations!