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Q. What causes microphonic vibrations? A. Microphonic vibrations are caused by internal component electronics like transformers and relays, motors, and external vibrations like sound waves. These vibrations create mechanical impulses inside vacuum tubes, inducing small parts to move, altering their capacitance and voltage, resulting in amplified distortions. Inside tubes, alternating opposing charges between plate and filament cause those parts to vibrate. (Basic Einsteinian physics also come into play, with rapid vibrations causing frequency-shift phenomena.) Symptoms of tube microphonics can be fuzziness throughout the frequency spectrum, high-pitch "glare," blending of similar frequencies, acoustical feedback, and mushiness in the soundstage. You may hear emphasis of sibilant sounds (s, z, ch, etc.) in vocals. HAL-O Vacuum Tube Damping Instruments significantly reduce all forms of microphonic distortion.   Q. Isn't adding weight to a tube to lower its resonance frequency all that's necessary to eliminate microphonics? A. No. Although each tube has a primary resonant frequency, like any instrument, or any instrumental note, you have octaves, harmonics, and subharmonics directly associated with that frequency, so lowering resonant frequency does not deliver a whole solution. Separate parts within a component each have different prime resonant frequencies. Some of the most detrimental microphonic vibrations occur at very high frequencies that are not directly associated with common resonance. We believe the most functional damping device will not damp any frequency in particular, but will absorb vibrations evenly across the whole spectrum.   Q. What's the advantage of the HAL-O over O-rings, Top Hats, etc? A. The overall advantage is that HAL-O damping instruments bring out the highest potential in your tube gear, resulting in better sound. Here are some observances we've made: Top Hats: These are basically lead weights placed on tubes to keep them from vibrating. Top Hats help define the "punch" and clarity of tube sound. They must be glued to your tubes, a hassle. HAL-O Damping Instruments are easier to use, and we believe deliver a better result. Brass Rings/Tube Anchors: Like lead, brass is heavy and lowers the resonant frequency of tubes and heightens their dynamic response. Microphonic distortions are effectively reduced also. Brass heats up though, and holds heat. Our tests with brass Tube Anchors resulted in input/driver tubes running an average of 33 .8º F hotter than without Anchors (SFS-80 amplifier with ambient room ventilation). Some users have reported shortened tube life using brass Tube Anchors. Instead of using massive weight, HAL-O Damping Instruments effectively control distortion by absorbing vibrations with a firm, yet gentle touch. Pearl Tube Coolers: With adequate ventilation, these heat sinks keep tubes cooler, potentially extending tube life (without ample ventilation though, they actually cause tubes to run hotter!). At controlling microphonics, they are marginally effective when new. Rubbery O-rings holding the heat sink against the tube can gradually become brittle from the heat, resulting in gradually increasing, uncomfortable distortion. While HAL-O Damping Instruments keep your tubes at about their normal temperature, you get a much purer sound and better reduction of microphonics. Lots of people have replaced their tube coolers with HAL-O Damping Instruments and realized immediate sonic improvements. Duende Criatura Tube Rings: These Teflon/titanium clamps are great at bringing out sharp dynamics and clarity, though frequency response seems a bit thin in places (lower-midrange in particular). A slight upper-frequency "twinge" can be overcome by lightly sandblasting the Teflon ring. Soft-tempered titanium is practically useless as a clamp; like soft copper, it has no spring -action. The metal bends outward and then just stays there, offering little or no inward tension -- this can be vastly improved by replacing the titanium ring with a spring-tempered nickel alloy or non-magnetic stainless steel ring to get a firmer grip on the tube (and with a more full-bodied sonic result). To keep tubes from getting too hot, tube rings should be placed near the top of the tubes where they are sometimes least effective (and small -signal tubes still run about 10 degrees F. hotter than with HAL -Os). Overall though, a pretty good tube damper, delivering a pleasant-to-listen-to result. Neoprene and nitrile O-rings help microphonics a little but after a while, these materials get brittle from the heat and the rings become ineffective. Their relatively high durometer (hardness) limits their ability to absorb subtle vibration in the first place. After all, like other O-rings, they're made to be used as seals, not as vacuum tube dampers. Teflon-coated silicone O-rings fare better. These industrial seals tend to improve the sound of tubes suffering particularly from microphonics, adding only a slight frequency coloration. Some users have reported great results with these. With some tubes, however, they induce a bloopy, muddied bass and/or high-frequency loss and/or upper-mid harshness. Elastomer O-rings: Such as silicone, 3M and Audio Research tube dampers. Elastomers can work pretty well at absorbing vibrations, but some users have reported noticeable muddiness and loss of midrange information. Elastomer rings can fuse to your tubes or eventually crack and wear out. O-Rings placed around tubes have no place to disperse vibrations; by contrast, HAL-O damping pads absorb and disperse vibrations into their surrounding "C" ring. Sorbothane Dampers: Sorbothane is heat resistant only to 200° F. (93.5° C), after which the material melts. According to Sorbothane's website data, the material begins losing its vibration-absorbing ability after reaching a temperature of only 160° F. Sorbothane simply does not hold up to vacuum tube heat requirements. Tube Sox: These are woven tubes made of fiberglass-like Kevlar that slip over your vacuum tubes. These become stiff with age, due to UV radiation and heat, losing their flexibility and damping quality. Shun Mook resonators: These are small African blackwood (Mpingo) discs placed on the top of tubes. Like ebony, Mpingo tends to enhance tonal qualities, but of itself does not reduce microphonic distortions much. Tweaks: Here are a couple of do-it-yourself alternatives: Wire twist ties wrapped with Teflon tape. This "damper" can achieve a miniscule improvement, but is barely worth the effort. Automotive heater hose or Teflon shrink wrap surrounding tubes . Generally improves the quality of badly microphonic tubes, but insulates the tubes, causing them to run hotter than they should. Can make excellent-sounding tubes sound worse.   Q. I have heard that no damper is best if microphonics are not an issue. A. In the past, most tube dampers added some "coloration" to the music or altered some areas of frequency response; if your tubes were performing well, it was best to leave them alone . However, we have never heard a tube amplifier or preamp that did not suffer from the effects, to some detrimental degree, of microphonic distortion. We believe that microphonics is always an issue, even when not considered a major problem. HAL-O damping instruments address microphonics without coloring the music or altering the frequency response (if your tubes were absolutely free of microphonic influence, HAL-O damping instruments would have no affect on them). If you have a good-sounding tube preamp or amp and don't perceive any microphonic "issues," you would probably be surprised after placing HAL-O damping instruments on your tubes. With a sudden increase in musical clarity, you would realize you had been listening to some amount of "grunge" and distortion all along. You'll find there is much more "music" in the music.   Q. Having "some/little" microphonics in the tubes is important (most tube audiophiles know this)--- it's one of the things that make tubes sound the way they do (over solid state). By eliminating microphonics, the tubes' sound would be totally changed (perhaps lose that warm, open/layered, and transparent quality). What are your thoughts/comments on this? A. Unwanted microphonics add fuzziness to musical detail, blur the focus, add glare, and cause other distortions. The HAL-O eliminates these problems. We believe tube gear generally sounds better than solid state for reasons other than "microphonics." We don't think it's microphonic distortions that audiophiles really want to hear, but rather the soundwave phase-shifts, natural reverberations, and other nuances that occur in a live music environment. HAL-O Damping Instruments reveal more of this acoustic dimension and subtlety. Ironically, some tubes that are the most sensitive to microphonic distortions are also the most revealing with musical nuance. Many HAL-O users have found that HAL-O Damping Instruments enhance the unique qualities of their tubes. For example, a "warm" sounding tube sounds better because the tonal qualities are more pure and true-to-life. The "warmth" is still there, with a more focused soundstage. Open-layered and transparent qualities are enhanced because the background is quieter, imaging is better focused, decay has more of a purity of tone. Tubes that work well on the high end have less fuzz and glare, better presence, stronger dynamics, while keeping the same high-end frequency response.   Q. Is it possible to overdamp tubes? A. "Overdamping" of vacuum tubes is usually an effect of unwanted resonance. Because HAL-O Damping Instruments reduce vibrations without introducing resonance of their own, the tube's musical/electronic "field" remains true, resulting in an open and lively, "undamped" presentation. In some audio systems, tube microphonics cause upper-frequency emphasis or harshness, so the enthusiast compensates for this by "damping" or attenuating upper frequencies elsewhere with choice of cables, interconnects, speakers, or other "tweaking." Consequently, if the source of that upper-frequency emphasis is suddenly corrected and made true, the overall result might seem overdamped or dull. With so many variables involved with audio reproduction, results cannot be predicted 100% when introducing a new element. Sometimes, correcting tube microphonics might initially deliver an unexpected result. It might take some experimentation and "tweaking" to get the desired synergy. If, in rare cases, HAL-O Damping Instruments seem to "overdamp," their effect can usually be lessened by adjusting their placement on the tubes.   Q. Will HAL-O Vacuum Tube Damping Instrument make ordinary, inexpensive tubes sound as good as rare and expensive NOS tubes? A. Sometimes, but not always. Our experience has been that the more a tube suffers from microphonic distortion, the more it will be improved with the HAL-O Damping Instrument. We have seen significant improvements in the performance of most every kind of tube, including some of the world's best NOS tubes such as Amperex, Siemens, Mullard, Telefunken, and others. Different tubes each have their own unique character, so determining whether one is better is sometimes a matter of personal preference.   Q. Will the HAL-O Damping Instrument cause my tubes to run hot? A. No. Tubes are "cooled" naturally by air rising up their sides (tubes heat the air, causing it to rise, with fresh air swooping in to take its place). The HAL-O open-air design allows for natural cooling. Our tests have shown that tubes will run at about the same overall temperature with or without HAL-O Damping Instruments. (Most tubes perform optimally at temperatures associated with ambient room-temperature operation).   Q. Will HAL-O isolation pads melt to my tubes? A. No. You can reposition or transfer your HAL-O Damping Instruments whenever you like. The isolation pads retain their vibration-absorbing qualities, remaining soft yet firm, with continuous contact with temperatures beyond 420º.F (216º.C). If exposed to constant temperature much above this, the isolation pads might gradually become brittle where they contact the glass, but will not melt. For extremely hot tubes, "X"-series damping instruments are recommended. X-Treme Temp Damping Instruments have ceramic-fiber sleeves surrounding the isolation pads, which increase the heat resistance of the pads to an extreme 540º.F (282º.C), keeping them soft and compliant, eliminating any possibility of damage to the damping instruments or your tubes.   Q. Do you really need dampers for the output power tubes? A. We have found that, in general, output tubes are just as sensitive to microphonic distortions as small-signal tubes. Because of their close proximity to transformer hum and other factors, power tubes often suffer considerably from microphonics.   Q. How much space around the tubes is needed for the damping instruments to fit. A. The damping instruments extend about 1/2 inch around. Tubes standing quite close together are no problem, however. With a pair of tubes, the C-shaped HAL-O rings can be positioned so that the open parts face each other. With three or more tubes in a row , damping instruments can be placed vertically, at a slight angle, to accomodate extremely close tubes.   Q. My amp has a ribbed cage surrounding the tubes. Will the dampers fit? A. Some amps, like KR Antares, and some components like Shanling CD players, have ribbed cages surrounding each tube. Damping instruments will fit in-between the layers, but it's easy to just remove one of the layers to allow plenty of room.   Q. Is it okay to replace the metal sleeves around my tubes with HAL-Os? A. Metal sleeves (some are spring-loaded) are sometimes placed around tubes to prevent radio frequency interference and/or to hold them in place in a hostile environment. In home audio applications, the sleeves have negligible utility and sometimes add a bit of weird-sounding influence. You can safely remove the tin cans and install HAL-O Damping instruments in their place. We have many customers who have done so and gotten astounding improvements.   Q. Would upgrading my tube sockets eliminate the need for tube dampers? A. Superior quality sockets usually improve sound quality, and lessening microphonic vibrations is one of the reasons. A socket upgrade, however, does not reduce microphonic distortions as much as the HAL-O Damping Instrument does. In fact, upgrading to HAL-O dampers greatly diminishes the need of switching to higher quality sockets.   Q. How will the HAL-O dampers work on the HORIZONTAL 6922 input and driver tubes? A. The HAL-O Damping Instruments will work perfectly on tubes in the horizontal position (or even upside-down!)

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