Thanks for that Fordmod, and good luck in finishing your Rek-o-Kut project!!
And now for a Tale of Idler Rumble. A while back I delivered both a Giant Direct Coupled Garrard 401 and a Giant Direct Coupled Glass-Reinforced Lenco (GDCGRL...say that ten times fast!!) to the same fellow, who after hearing one of my GDCGRL for only twenty minutes agreed to trade his Anniversary-edition Oracle Delphi MKIV (black and gold) against the deal. He had subwoofers set up in the corner of a rather large listening room, and a flimsy Target shelf for the unsuspended 'tables right between them, and close. As background, I advised him, as I do all who receive Lencos or other idlers from me, that the best platform I have found is stone bonded to acrylic or Corian, acrylic being on top. This is because stone will not flex and so is much less likely to transmit furniture-created rumble (low-frequency vibration of the sort familiar to other unsuspended decks, like Regas), and acrylic makes it all sound more natural, and damps the stone's ringing, being a CLD sandwich. This has the result of eliminating low-frequency feedback, and of focusing the idler's great strengths, which actually are everything and everywhere, but especially, against a background of belt-drives, transient speed, SLAM, limitless and tight and detailed bass information, incredible timing.
Now, bolting or Direct Coupling an idler, already extremely powerful in the bass, to a large inert mass, creates limitless bass reach, detail and speed (Direct Coupling even more so), which in turn means that any rumble, whatever the origin, will be picked up and amplified. The Garrard/SME V/Dyna XX-1 on the Target shelf was fed into a fully-tubed phono stage (Audio Space), which was, to boot, microphonic. Immediately the first record was played, unacceptable levels of rumble were heard, and so I advised him to simply sit the Garrard on the floor. Much better, but now the opening grooves on each LP - which are distorted by the process of spreading the vinyl outwards in the pressing, meaning the outer edges/opening grooves are distorted in the cooling/hardening vinyl - caused a low-frequency feedback loop which overloaded the phono stage and drove it into oscillation. Plus, there was some rumble/noise still being heard at low levels. So we found some sound-deadening blocks and stuck one under each of the three carriage-bolt feet. Noise now gone, the oscillation yet remained, and we inserted a solid-state phono stage, noise now greatly diminished, vanishingly so. So things stood until I delivered the Lenco.
The fellow didn't want to spring immediately for a stone platform, so we compromised: I built him a new shelf made from my usual recipe of birch-ply and MDF, which we plopped down into the Target stand, and he ordered an acrylic slab. We set up the Lenco on that, no acrylic slab yet, and heard some rumble/noise, and some of that old feedback oscillation in the opening grooves (tubed phono stage back, but with new, less microphonic tubes now). We put the sound-deadening blocks in, which eliminated the noise, but which to my ears also eliminated much of the Lenco power, magic, speed and bass impact. But, he was very happy (remember he had a high-end belt-drive before ;-)), and I left it at that for now, yet still dissatisfied.
Eventually he sent me news of his acrylic slab being ready, and I went over to glue it (using 3M spray adhesive which doesn't react with rubber platter mats either). We first went about finding the best combination of phono stage without the acrylic slab, and settled on the John Curl-designed Sota active step-up fed into the MM section of the tubed phono stage as having the best balance of musicality (much more musical than the solid state phono stage) and silence (MC stage too noisy with no appreciable increase of musicality). Now it was starting to sound good.
We bonded the acrylic to the Birch/MDF platform, and set up the Lenco on that, this time without the sound-deadening blocks. ALL rumble and noise was now completely gone, regardless of volume (and we were playing LOUD), and the improvement in sound quality was truly shocking. NOW the Lenco was indeed Mighty, with that familar sense of untapped yet ever-present limitless power (and the comparison to the Amazon in full flow is still the best description of the Lenco sound so far), and incredible delicacy, SLAM, limitless duynamics, air, imaging, transient speed with decaying notes fully recovered and atmospheric, and incredible bass detail and information which is, quite simply, inaudible and not present on belt-drives. In this extremely hig-end system, the sonic results were quite simnply awesome and overpowering, the same sound which easily outperformed a fully updated $11K EMT 930 idler wheel drive back on Cyprus.
Which is to say, that properly set-up idlers do not rumble inherently, regardless of the low-frequency levels reacheable by any system, subwoodfers or not. What is happening is that the idlers' abilities to delve extremely deeply in the bass (due to the vastly-superior torque and speed stability in the face of problematic stylus force drag) means that any low frequency noise is picked up, amplified, and often causes a feedback loop which endlessly cycles and re-amplifies the noise. Of course, the idlers themselves must be meticulously set-up and restored in order to remove any possible sources of noise. Direct Coupling lowers the noise floor yet more to astonishing levels of quietness (while increasing every audiophile aspect from detail retrieval through imaging to bass information), and finally, setting up on a non-flexing suitably damped platform (which means extremly lightly damped, like gluing acrylic to stone to deaden ringing but not introduce energy-killing/sucking phenomena) eliminates all noise which "excavating" the idlers' abilities in all audiophile areas, especially transient speed, focus, SLAM, bass and timing/rhythm (Pace, Rhythm and timing, PRaT).
Finally, the recipient, extremely difficult (when I delivered the Lenco and Garrard he set up a lab with scopes to measure noise and performance before he would insert them in his system, and he is EXTREMELY sparing with compliments or positive reports) now utterly convinced, bought a granite slab within a couple of days, and has sent me the following e-mail: "Can't believe what a slab of granite will do. Great improvement on the bass .....you can hear each note clearly..........better focus on the mid ...........and the little edginess in the high is gone too. Best $60 I spent in many years!!" Now, to highlight just how serious about audio this fellow is, he is planning on buying a $100K preamp for his system, has been an audio distributor (the second to favour properly set-up idler-wheel drives, specifically Lencos, as opposed to high-end belt-drives), and is going into manufacturing of tubed electronics (also the second manufacturer of tubed electronics to be seduced by the Mighty Lenco, the other being Roger Hebert of Wyetech fame).
Anyway, consider a CLD slab of acrylic bonded to stone as practically mandatory in order to get the most out of your respective idler-wheel drives all, and enjoy the sound of your Mighty Idlers!!
