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FAQ's |
FAQ's
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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. 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. Herbie's 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?
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A. No. Although each tube has a primary resonant frequency, you have octaves, harmonics, and subharmonics directly associated with that frequency, and internal parts with different and unique resonant qualities. The material used for a weight, i.e., brass or lead, will influence the tubes' results with its own character and the more mass, the more its character will dominate. A noncompliant, rigid material will vibrate to some degree right along with invasive microphonics. Simply loading weight to a tube does not deliver a whole solution and is usually counterproductive in some ways.
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Herbie's damping instruments do not work by adding weight. A titanium C-ring weighs only a few grams, yet its spring tension provides resistance to vibration equal to many times its weight without the drawbacks of weighing down the tube. With vibration-absorbing pads interfacing the C-ring and tube, each damping instrument works similarly to holding a tube with your fingertips.
Q. Will Herbie's tube dampers cool my tubes or cause them to run hot?
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A. In ambient air, tubes are "cooled" naturally by air rising up their sides (tubes heat the air, causing the air to rise, with fresh air swooping in to take its place). Herbie's open-air designs allow for natural cooling. Tests have shown that tubes will run at about the same overall temperature with or without our damping instruments. (Audio tubes generally perform best in ambient temperature without being artificially cooled or heated.)
Q. Do you really need dampers for output power tubes?
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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. The same is true with rectifier tubes; with reduced microphonics, a truer rectified current improves everything.
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With a limited budget, it's not always feasible to install damping instruments on all tubes in a system. Beginning with the source/preamp and rectifier tubes is generally the most frugal approach.
Q. Will Herbie's tube dampers extend tube life?
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A. We believe that optimal tube life is extended considerably by damping bulb vibration. This has been thoroughly proven with ordinary light bulbs, which are vacuum tubes. Although there seems to be little empirical data, plenty of anecdotal evidence supports this to be true also with audio tubes. Regardless of whether usable tube life is extended though, music will sound better with reduced microphonics.
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Vacuum tubes tend to become more sensitive to microphonic distortions as they get older. Herbie's damping instruments will keep your tubes sounding like new for years and years to come.
Q. What's the advantage of Herbie's dampers over other kinds of tube dampers?
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A. The definitive advantage is that Herbie's damping instruments bring out the highest potential in your tube gear, resulting in better sound that's more enjoyable to listen to. Here are some observations we've made:
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Duende Criatura Tube Rings: Although these European Teflon/titanium rings are great at bringing out a sense of detail and clarity, they don't fully reveal the deeper "texture" of each note, and lower/mid frequencies seem a bit thin at times. To keep tubes from overheating, they should be placed near the top of the tubes where they are sometimes least effective. Though lacking the punch, power and nuance of UltraSonic Rx damping instruments, they're not bad dampers overall, delivering a pleasant result. Grade: B-.
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Pearl Tube Coolers: With adequate ventilation, these heat sinks keep tubes cooler, potentially extending tube life (without ample ventilation though, they often cause tubes to run hotter!). At controlling microphonics, they are marginally effective when new. Rubbery O-rings holding the heat sink against the tube gradually become brittle from the heat, resulting in gradually increasing, uncomfortable distortion. Grade: D.
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Tube Anchors/Brass Rings: Though awkward to work with, Tube Anchors by MapleShade are excellent sonically, the only dampers we have tested that play in the same league as our best damping instruments. Massive brass clamped around a tube, however, deprives the glass bulb of air ventilation needed for cooling. Our tests with brass Tube Anchors resulted in input/driver tubes running an average of 33.8º F hotter than without Anchors. Other manufacturers also make brass or copper sleeves and mistakenly imply that they are tube "coolers." Some users have reported breaking the glass envelope when clamping Tube Anchors to the tube. Grade: B.
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Absorb-Gel (Allnic): These are extension sockets with a gel material inside. We have found that damping tube sockets can sometimes be effective at reducing microphonics, but damping the bulb glass is much more effective and the results more consistent amongst various tubes and components. Damping the socket and tube both can be mutually effective; placing a ring of Permatex Blue Silicone Gasket Maker (available at auto parts stores) around tube sockets dampens them quite effectively, without the drawback of having an additional set of pins/sockets for each tube, keeping a more direct electronic signal intact. (Because Allnic Absorb-Gel Dampers damp vibrations under the tube pins, the benefits are minimal compared to damping the socket directly contacting the tube pins.) In almost all cases though, Herbie's Damping Instruments provide optimal results without having to worry about damping the sockets. Grade: Complementary tweak.
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Cool Damper by EAT (Euro Audio Team): Herbie's Audio Lab has tested this fine-looking tube damper and found it to be a bust. These dampers reduce tube microphonics, but the sonic result is poor. Lower midrange frequencies are bland; acute dynamics tend to be "rounded" without energetic attack and decay; high frequencies are well-represented, but lack many of the intangibles that give a sense of live performance. As coolers, they fare even worse. Although the damper appears to be designed as a heat sink, the thermally conductive interface between the glass bulb and aluminum fins is woefully inadequate for the device to function as such. Grade: D-.
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Top Hats: These are lead weights placed on tubes to keep them from vibrating. Top Hats help define the "punch" and clarity of tube sound, but also introduce a telltale lead coloration (muddy bass, high-frequency "twang" factor). They must be glued to your tubes, a hassle. UltraSonic damping instruments are easier to use, and without a doubt deliver a better result. Grade: C.
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Tube Sox: These are woven tubes made of fiberglass-like Kevlar that slip over your vacuum tubes, reducing microphonics quite effectively with minimal attenuation of some higher frequencies and some loss of inner detail. They become stiff with age, due to UV radiation and heat, losing their flexibility and damping ability. No-brainer verdict: not a good product. Grade: F.
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Neoprene and nitrile O-rings help microphonics a little, but after a while these materials get brittle from tube 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. Grade: F.
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Teflon-coated silicone O-rings fare better. These industrial seals, available from McMaster-Carr and other hardware suppliers, tend to improve the sound of tubes suffering particularly from microphonics or tube rattle, adding only a slight frequency coloration. Some users have reported satisfactory results with these. With some tubes, however, they induce a bloopy, muddied bass and/or high-frequency loss and/or upper-mid harshness. Because Teflon softens and elongates with higher temperature, results can be unpredictable when in direct contact with the radiant heat of tube glass. Grade: varies from B- to D.
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Elastomer O-rings: Such as silicone, 3M and Audio Research tube dampers. Silicone o-rings can work pretty well at reducing vibrations, but some users have reported noticeable muddiness, loss of midrange information, and/or "peaking" at certain bass frequencies. Elastomer rings can fuse to power tubes or eventually crack and wear out. O-Rings placed around tubes have no place to disperse vibrations; by contrast, all Herbie's dampers feature isolation pads to absorb and disperse vibrations into their surrounding "C" ring. Grade: C+.
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Caution: silicone O-rings like those sold on ebay as "tube dampers" do not hold up to some hot-running power and rectifier tubes for the long haul -- "Aerospace High-Temperature Silicone" handles ambient temperatures up to 450° F for a good while, but continuous radiant heat from output and rectifier tubes (which generally run about 480° F) will gradually plasticize the silicone and render it useless. They are inexpensive enough to replace every once in a while though, and often provide satisfactory relief for guitar amp tube rattle issues. These O-rings hold up very well with cooler, small-signal preamp tubes.
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Sorbothane: 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. With cool-running tubes that it can be used with, Sorbothane tends to cause "bloopy" bass and attenuate the higher frequencies. (Herbie's Audio Lab highly recommends that Sorbothane be used absolutely nowhere in an audio system. This material will often achieve a localized sonic tradeoff that seems beneficial, but literally contaminates the sonic integrity of the system as a whole.) Grade: F+.
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Shun Mook resonators: These are small African blackwood (Mpingo) discs placed on the top of tubes. Unlike Gabon ebony, which smooths out acute microphonics, Mpingo (not an ebony, it's of the rosewood family), produces a vibrant resonance that can enhance a recording's sense of vitality. At Herbie's Audio Lab, we believe that reducing microphonic distortion to unveil the energy and spirit of the original recording session is a more honest, and ultimately more effective, approach. Grade: System Dependent.
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DIY: Here are a few do-it-yourself alternatives:
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Wire twist ties wrapped with Teflon tape (the kind of tape used to wrap pipe threads). This "damper" can achieve a worthwhile, though minimal improvement. Many tweakers use Teflon tape alone, without wire, just wrapping tape around the tube. Although this microphonics remedy doesn't bring out the highest potential in your tube gear, results generally are acceptable for the price involved and will rarely do any harm sonically. Grade: C.
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Automotive heater hose or Teflon shrink wrap surrounding tubes. Sometimes 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. Oftentimes causes "bloopy" or choppy bass, weird highs. Grade: C-.
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Mortite: Rope caulk is a great vibration-absorbing material for use with internal component chassis, loudspeaker baskets and many other applications (and highly recommended by Herbie's Audio Lab). Not advised for vacuum tubes, however. Mortite and other brands of rope caulk have a high temperature range of only 150°F (66°C). The material might hold up to the heat of small-signal tubes for an audition or two (which will probably yield good sonic results), but before long, Mortite will turn foamy, smoke and burn, partially vaporize and melt into a pathetic mess (similarly, Blu-Tak has very poor high-temperature range and will melt readily on vacuum tubes). Grade: F.
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Babbitt putty, a high-temperature material (978°F) with some qualities similar to Mortite, can be used effectively on vacuum tubes and yields excellent sonic results, but exudes an offensive odor. Grade: B+.
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Oil-filled bottle. Effective? perhaps. Practical to use? perhaps not. Grade: Not Evaluated.
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Herbie's Tube Dampers:
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Original Teflon HAL-O remains in our lineup because of its high value for damping interconnects, cables, plugs, and capacitors. Excellent results with small-signal tubes, also. Grade: B.
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MidFi+ has no peer in its price range and has an added bonus of helping to bring out a deeply extending bottom end. Grade: B-, for value: A-.
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PEEK HAL-O, a former top-of-the-line damping instrument packs a dynamic punch, yet is soft and delicate when the music calls for it. Grade: B.
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BlackBery HAL-O with black berylium C-ring and soft isolation pads tends to preserve that warm, "tubey" sound that some people prefer while bringing out a little more resolution. Grade: B+
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Original UltraSonic, our previous default recommendation for all home audio tubes, achieves a highly detailed sonic result and good cost-effect ratio. (Original UltraSonics can tend to be slightly "harsh" or "dry" with some systems.) Grade: B+.
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Guitar Amp UltraSonic, designed to minimize microphonics, oscillation, and tube rattle in severe vibrational environments as found in a combo guitar amp. Works superbly with home audio systems as well, delivering a highly linear and spacious soundstage with plenty of "air." Grade: A.
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UltraSonic Rx had been cooking on Herbie's "back burner" for several years. Because of the extremely high cost of perfluoroelastomer O-rings surrounding the isolation pads, we considered this product would be too expensive. When at last a prototype was developed with a modified Teflon polymer and just the right perfluoroelastomer formula, we knew that the sonic perfection we long sought was in hand and must be made available to other audiophiles regardless of the cost. By making our own O-rings from sheet material, we are able to offer this product at a cost-effective price. The sonic result with a highly resolving audio system is uncanny. It's the closest we've experienced to being in a recording studio monitoring an actual performance "live" or being in the presence of a live event. Grade: A+.
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Preamp UltraSonic, introduced as a lower-cost alternative to UltraSonic Rx for small-signal tubes, frees tubes to deliver an unblemished audio result. Grade: A.
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Q. How do I decide which kind of dampers to use for my tubes?
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To bring out the very best potential of your tube gear, Preamp UltraSonic, UltraSonic Rx, and Guitar Amp UltraSonic all deliver the goods. Though all versions of Herbie's Damping Instruments deliver linear frequency response with little or no tonal coloration, each provides subtle differences in microdynamic impact, just as different brands and labels of the best NOS tubes have subtle differences in dynamics.
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Descriptions of all our damping instruments are brief and straightforward, so you don't have to read "between the lines" to understand the general qualities. For example, if your system is somewhat "dry" or analytical, UltraSonic Rx would be the best choice to give you a more fluid, musical result with no loss of detail. For a system that has plenty of fluidity, original UltraSonics will bring out more intricate detail at a lower cost. With many systems, a hybrid combination is ideal for cost/effectiveness: for example, use Preamp UltraSonics for the small-signal/preamp tubes, UltraSonic Rx for rectifier and output tubes.
Q. Are Herbie's damping instruments completely non-magnetic?
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A. Yes.
Q. Will Herbie's tube dampers make inexpensive tubes sound as good as rare NOS tubes?
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A. Oftentimes, the main difference between premium-quality and ordinary tubes is their ability to deal with microphonics. By reducing the microphonics factor, Herbie's damping instruments allow a greater variety of tubes to compete on a more level playing field. Then again, inherently better tubes will usually sound even better with damping instruments. In general, the more a tube suffers from microphonic distortion, the more it will be improved with damping instruments. We have seen significant improvements in the performance of most every kind of tube, including some of the world's best NOS tubes like Amperex, Siemens, Mullard, Telefunken, and others. For specific examples, Siemens CCa tubes present an extremely linear, uncolored musical result, but tend to have a slight bit of microphonic "fuzz" on the dynamic edges; Herbie's Damping Instruments eliminate that artificial fuzz while maintaining the same uncolored integrity. Amperex white label 6922 PQ'a are amongst the finest tubes ever. With PQ's, UltraSonic Rx Damping Instruments reveal just a little more of the inner, intricate nuance present in the music by lifting a thin microphonic veil.
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Tubes that are most revealing of subtle, sonic nuance are often equally sensitive to microphonic distortion. UltraSonic Rx really brings out the best in these tubes. Different tubes each have their own unique character, so determining whether one sounds better than another is usually just a matter of personal preference. Almost all, however, do a better job with Herbie's Damping Instruments.
Q. I have heard that no damper is best if microphonics are not an issue.
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A. In the past, most tube dampers added an abundance of "coloration" to the music or altered some areas of frequency response; if your tubes didn't suffer terribly, it was best to leave them alone. However, we have never heard a tube component that did not suffer from the effects, to some detrimental degree, of microphonic distortion.
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If you have a great-sounding tube component and don't perceive any microphonic "issues," you would probably be surprised after placing damping instruments on the 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. Is it best to use one or two dampers per tube?
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A. In almost all cases, one damping instrument is all you need, reducing audible microphonics so efficiently that a second usually adds little or no additional effect. With extremely microphonic tubes and with some huge tubes like 8.5" tall 805 tubes, however, a second damping instrument is sometimes beneficial.
Q. Having some microphonics in the tubes is important---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 changed (perhaps lose that warm, open/layered, and transparent quality). What are your thoughts/comments on this?
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A. Unwanted microphonics add fuzziness to musical detail, blur the focus, add glare, and cause other distortions. Herbie's damping instruments diminish or eliminate these problems. We believe tube gear generally sounds better than solid state for reasons other than "microphonics."
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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. Herbie's 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.
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Many audiophiles have found that damping instruments enhance the uniqueness of certain 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, but 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 and texture. Tubes that work well on the high end have less fuzz and glare, better presence, stronger dynamics, while keeping the same high-end response.
Q. Where is the best place on tubes to position dampers?
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A. Although exact placement isn't critical, Herbie's damping instruments are usually most effective in the area approximately 1/3 of the way down from the top. Some experimentation might reveal a "sweet spot" where they sound best (many customers have reported best results with damping instruments placed even with the tube's top getter plate, some around the middle, and a few have preferred placement near the top or bottom).
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With shouldered tubes, a damping instrument can be placed either around the widest part of the "shoulder" or at the base of the "neck," where the neck meets the shoulder.
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Bulb-shaped tubes use a single damping instrument around the widest part of the tube.
Q. Do tube ampers need a break-in period?
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A. Yes. Original UltraSonics need a break-in each time they are used; the fiberglass-filled sleeves on the isolation pads are somewhat brittle when cold and need to warm up to achieve best results. They will simultaneously break in with tube warm-up, however, so break-in time is really not much of an issue. UltraSonic Rx, Preamp UltraSonic, and Guitar Amp UltraSonics are ready to go, but improve gradually with age as the isolation pads further cure from tube heat and achieve a somewhat "tighter" resolution.
Q. Will isolation pads melt to my tubes?
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A. No.
Q. Is it possible to overdamp tubes?
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A. Herbie's damping instruments simply reduce vibrations and their associated distortions, resulting in an a more open and lively, seemingly "undamped" presentation. Eliminating microphonics at the tubes, however, might cause unwanted resonances or other anomalies elsewhere in the system to become more apparent. Audiophiles sometimes "tweak" their systems with Sorbothane or other damping materials to attenuate overly bright or sibilant tube microphonics; this artificial attenuation can cause the system to then seem overdamped when microphonics are subsequently corrected at their source.
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Conversely, introducing damping instruments to a system can sometimes "overclarify" by revealing the true musical signal the tubes are receiving. Overly "bright" cables might be exposed for their true nature or coloration from metal cones might come through more distinctly.
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If, in rare cases, a damping instrument seems to "overdamp" or "overclarify," its effects can usually be lessened by simply placing it close to the base of the tube or near the top. Like introducing any new "tweak" or accessory, sometimes it takes adjustments elsewhere in the system to bring everything together at the next level, i.e., toe the speakers in or out a little, adjust footers, address component isolation issues, adjust customary volume settings. Almost always, however, sonic benefits are achieved without additional adjustments.
Q. How much space around the tubes is needed for damping instruments to fit.
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A. Damping instruments with titanium C-rings extend less than 1/4" from the tubes. Although the pads extend almost 1/2", they can be positioned on tubes as close as 1/4" from each other, or even closer if only a pair of tubes (by placing the open ends of the C-rings facing each other). PEEK and Teflon damping instruments require a little more space.
Q. Is it okay to replace the metal sleeves around my tubes with dampers?
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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 (and for international shipping). In home audio applications, the sleeves have negligible utility and sometimes add a bit of weird-sounding influence. You can safely remove them and install damping instruments in their place. We have many customers who have done so and reported satisfactory improvements.
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Likewise, some components have little cages around each tube, to protect the tubes from errant thrown balls, children, pets, or to alter proximate electromagnetic waves. These cages can be removed and damping instruments placed on the tubes for significant sonic improvement.
Q. How will Herbie's dampers work on the HORIZONTAL 6922 input and driver tubes?
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A. Herbie's damping instruments work perfectly on tubes in the horizontal position (or even upside-down!).