UltraSonic FAQ's ...

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. UltraSonic 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, 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.

UltraSonic 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 microphonics-absorbing pads interfacing the C-ring and tube, each damping instrument works similarly to touching a tube with your fingers.

Q. Will UltraSonic damping instruments cool my tubes or cause them to run hot?

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). The UltraSonic open-air design allows for natural cooling. Our tests have shown that tubes will run at about the same overall temperature with or without UltraSonic damping instruments. (Audio tubes generally perform best in ambient temperature without being artificially cooled or heated.)

Q. Will UltraSonic damping instruments extend tube life?

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.

Vacuum tubes tend to become more sensitive to microphonic distortions as they get older. UltraSonic damping instruments will keep your tubes sounding like new for years and years to come.

Q. What's the advantage of UltraSonics over other kinds of tube dampers?

A. The definitive advantage is that UltraSonic 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:

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 subtle "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 damping instruments, they're not bad dampers overall, delivering a pleasant-to-listen-to result.

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.

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.

Tube Anchors/Brass Rings: Though awkward to work with, Tube Anchors by MapleShade are excellent sonically, the only dampers we have tested that perform in the same league as UltraSonic damping instruments. Massive brass clamped around the tube, however, deprives the glass bulb of air ventillation 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."

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. (test results)

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, loss of high-frequency "twang" factor). They must be glued to your tubes, a hassle. UltraSonic damping instruments are easier to use, and we believe deliver a better result.

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.

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, 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.

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, UltraSonic damping pads absorb and disperse vibrations into their surrounding "C" ring.

A few words of caution: silicone O-rings like those sold on ebay as "tube dampers" do not hold up to 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. These O-rings will, however, hold up very well with cooler, small-signal preamp tubes.

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. With cool-running tubes that it can be used with, Sorbothane tends to cause "bloopy" bass and attenuate the higher frequencies.

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.

Tweaks: Here are a few do-it-yourself alternatives:

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. Wrap-around feature insulates tubes though, keeping too much heat in.

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.

Oil-filled bottle. Effective? perhaps. Practical to use? perhaps not.

Q. Why have previous HAL-O versions been discontinued?

A. In addition to functional advantages like keeping a better grip on the tube glass, better adaptability to different tube diameters, and superior long-term heat resistance, our present UltraSonic lineup achieves a more-perfect sonic result than previous HAL-O versions, with superior cost-effect ratios. UltraSonics have the accumulative advantages of various HAL-Os without any of their individual drawbacks.

Q. Is it okay to mix and match different kinds of tube dampers?

A. Yes. UltraSonic and HAL-O damping Instruments complement each other very well. For example, a combination of PEEK HAL-Os on the input and driver tubes with UltraSonics on the power tubes can be superb for a tube amp. Just be sure to keep stereo pairs the same. (Teflon and other previous HAL-O versions can also be mixed and matched with UltraSonic damping instruments.)

Q. Are titanium UltraSonic damping instruments completely non-magnetic?

A. Yes.

Q. Will UltraSonic damping instruments make inexpensive tubes sound as good as rare NOS tubes?

A. Oftentimes, the main difference between premium-quality and ordinary tubes is their ability to deal with microphonic vibrations. By eliminating the microphonics factor, UltraSonic 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 UltraSonics. In general, the more a tube suffers from microphonic distortion, the more it will be improved with UltraSonic 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.

Tubes that are most revealing of subtle, sonic nuance are often equally sensitive to microphonic distortion. UltraSonics really bring 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.

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 didn't suffer terribly, 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 recognized or considered a major problem. UltraSonic damping instruments address microphonics without coloring the music or altering the frequency response (if your tubes were absolutely free of microphonic influence, UltraSonic damping instruments would have no affect on them).

If you have a great-sounding tube preamp or amp and don't perceive any microphonic "issues," you would probably be surprised after placing UltraSonic 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. Is it best to use one or two dampers per tube?

A. In almost all cases, one UltraSonic damping instrument is all you need, reducing 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?

A. Unwanted microphonics add fuzziness to musical detail, blur the focus, add glare, and cause other distortions. UltraSonic damping instruments elimate 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. UltraSonic 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 audiophiles have found that UltraSonic 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 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 frequency response.

Q. Where is the best place on tubes to position UltraSonics?

A. Although exact placement isn't critical, UltraSonic damping instruments are usually most effective in the area between the middle of the tube and about 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).

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.

Bulb-shaped tubes use a single damping instrument around the widest part of the tube.

Q. Is it possible to overdamp tubes?

A. Unlike ordinary tube dampers, UltraSonic damping instruments simply reduce vibrations without introducing character of their own, resulting in an 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 to attenuate bright or sibilant tube microphonics; this artificial attenuation can cause the system to seem overdamped when tube microphonics are subsequently corrected at their source.

Conversely, introducing UltraSonic 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 metallic coloration from footers might come through more distinctively.

If, in rare cases, an UltraSonic 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 immediate; just place them on your tubes and enjoy.

Q. Will UltraSonic isolation pads melt to my tubes?

A. No.

Q. Do you really need dampers for 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. The same is true with rectifier tubes; with reduced microphonics, a truer current improves everything.

With a limited budget, it's not always feasible to install damping instruments on all tubes in a system. Beginning with the source/preamp tubes is generally the most frugal approach.

Q. How much space around the tubes is needed for damping instruments to fit.

A. UltraSonic C-rings extend less than 1/4" from the tubes. Although the pads extend almost 1/2", UltraSonics can be positioned on tubes as close as 1/4" from each other.

Q. Is it okay to replace the metal sleeves around my tubes with UltraSonics?

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 (or 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 UltraSonic damping instruments in their place. We have many customers who have done so and reported satisfactory improvements.

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 UltraSonic dampers work on the HORIZONTAL 6922 input and driver tubes?

A. UltraSonic damping instruments work perfectly on tubes in the horizontal position (or even upside-down!).

We will try to answer any question you may have about UltraSonic damping instruments:

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