UltraSonic Rx-9


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?

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. Most of the vibrations that cause microphonics have nothing to do with a tubes' resonant frequency. 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. Simply loading weight to a tube does not deliver a whole solution and is usually counterproductive in some ways.

Herbie's damping instruments do not work by mass loading. 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 stabilizing a tube with your fingertips.

Q: Will Herbie's tube dampers 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). 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?

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.

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.

For an amplifier or pair of mono amps that has lots of output tubes, damping every other stereo pair usually achieves fully satisfactory results; damping half the power tubes seems to achieve substantially more than 50% of the benefit.

Q: Will Herbie's tube dampers extend tube life?

A. We believe that optimal tube life is extended 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. 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?

A. Herbie's damping instruments are best at bringing out the highest potential in your tube gear, resulting in better sound that's more enjoyable to listen to. For a more comprehensive answer, please open new page.

Q: How do I decide which kind of dampers to use for my tubes? 

A. Herbie's damping instruments all deliver the goods. Though all versions 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.

The website description of each damping instrument is 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. With many systems, a hybrid combination is ideal for cost/effectiveness: for example, use UltraSonic SS for the small-signal/preamp tubes, HAL-O III for rectifier and output tubes.

Q: Are Herbie's damping instruments completely non-magnetic?

A. Yes.

Q: Will Herbie's tube dampers 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 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, Herbie's damping instruments reveal just a little more of the inner, intricate nuance present in the music by lifting a thin microphonic veil.

Tubes that are most revealing of subtle, sonic nuance are often equally sensitive to microphonic distortion. Damping instruments 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. 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.

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.

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?

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?

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."

We don't think it's microphonic distortions that most 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.

Excellent-quality damping instruments often enhance the uniqueness of 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 high-end response and ethereal sustain.

Q: Where is the best place on tubes to position dampers?

A. Although exact placement usually 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).

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: Do tube dampers need a break-in period?

A. UltraSonic Rx, UltraSonic SS, 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. HAL-O III needs no break-in period other than warming up along with the tubes.

Q: Will isolation pads melt to my tubes?

A. No.

Q: Is it possible to overdamp tubes?

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.

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 a bright coloration from metal cones might come through more distinctly.

If a damping instrument seems to "overdamp" or "overclarify," its effects can usually be lessened by simply placing it closer 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., adjust the speaker positioning a little. Sonic benefits are usually achieved right "out of the box" though, without additional adjustments needed.

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

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).

Q: Is it okay to replace the metal sleeves around my tubes with dampers?

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.

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?

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