UltraSonic Rx-9 Tube Damper



UltraSonic Rx Damping Instruments help to bring out the microdynamic speed, linearity, and detail of your source material. Besides reducing microphonic anomalies, Rx allows a freer musical flow, curing a harsh and stealthy "electronics factor" or "dryness" that ultimately ails even some of the most finely honed audio systems. Your tube gear will achieve a fluid, dynamic musical potential like it was engineered to do.

Mildly spring-tempered titanium C-ring holds three modified PTFE isolation pads. Each pad holds a specially formulated polymer O-ring against the tube glass.

Herbie's most popular damping instrument, UltraSonic Rx is appropriate for all audio vacuum tubes, handling radiant heat up to a constant 482° F (250° C). Scroll down for size listings, from smallest to largest.

UltraSonic Rx-Mini

For sub-miniature and Nuvistor tubes approximately 3/8" diameter (9.2mm to 10.4mm), including 5703, 6111, 6112, 6020, 6021, 6088, 6CW4, 6DS4, 6DV4, 6N16B, 7586, 7587, 7895, 8056, 8058, T3 bulb.

UltraSonic Rx-Mini: $26.98 ea.
4 or more: $26.29 ea.

UltraSonic Rx-7

For 7-pin miniature tubes and all tubes approximately 5/8" to 3/4" diameter (16mm to 19mm), including 0A2, 0B2, 0C2, 1S5, 12AE6, 12FK6, 12FM6, 12X4, 304B, 3A5, 3S4, 403A/B, 408A, 5591, 5651, 5654, 5654SQ/W, 6005, 6186, 6AK5, 6AK5W, 6AL5, 6AN4, 6AQ5, 6AQ6, 6AU6, 6BH6, 6C4, 6ER5, 6FG5, 6FQ5A, 6FS5, 6FY5, 6GK5, 6J1, 6J1P, 6J1P-EV, 6J6, 6N4, 6P17, 6X4, 6Z4, 7543, 9001, DCC90, DL92, EC90, EF95, M8100, OA2, OB2, OC2, SBA6. (Most 7-pin miniature tubes, at about 19mm diameter [3/4"], can also use UltraSonic 9.)

UltraSonic Rx-7: $28.66 ea.
4 or more: $27.92 ea.

UltraSonic Rx-9

UltraSonic Rx-9 Tube Damper

Fits miniature 9-pin tubes and all tubes 3/4" to 7/8" diameter (19mm to 22mm), including 10GV8, 12AT7/ECC81, 12AU7/ECC82, 12AV7, 12AX7/ECC83, 12AY7, 12AZ7, 12B4, 12BH7, 12BY7, 12BZ7, 12DW7, 12FQ7, 2C51, 396, 396A, 417, 5670, 5687, 5751, 5755, 5814, 5842, 5879, 5963, 5965, 6072, 6189, 6201, 6267, 6350, 6385, 6414, 6519P, 6688, 6829, 6840, 6922, 6955, 6973, 6AN8, 6BL8, 6BM8/ECL82, 6BQ5/EL84, 6AW8, 6AW8A, 6BQ7, 6BZ7, 6BW4, 6C19P, 6CA4, 6C45, 6CG7, 6CS7, 6DE7, 6DJ8/ECC88, 6E5P/6E5PI, 6EJ7, 6EU7, 6FQ7, 6GC7, 6GF7A, 6GH8(A), 6GU7, 6GW8, 6H23N, 6H30, 6H6PI, 6N1P, 6N2, 6N2P, 6N23P, 6N30, 6N30P, 6N3P, 6N6/6H6PI, 6N6P, 6P1, 6P1P, 6P1P-EV/6II1II-EB, 6S19P, 6S4, 6U8(A), 6V4, 7025, 7044, 7058, 7062, 7119/E182CC, 7189, 7199, 7308, 7788, 7AU7, 7DJ8, 8416, CCa, D3a, E288CC, E80CC, E80F, E88CC, EC86, ECC189, ECC40, ECC802S, ECC803/S, ECC81, ECC82, ECC83, ECC85, ECC86, ECC99, ECF80, EL821, ECL86, EF184, EF86, EL821, EL84, EL86, EM84, EZ80, EZ81, M8162, PCC88, PCL82, PCL86, SV83, (T-6 1/2 bulb).

UltraSonic Rx-9: $28.69 ea.
4 or more: $27.95 ea.

UltraSonic Rx-25

Fits all tubes approximately 1" to 1-1/16" diameter (23mm to 28mm), including metal 12SC7, 5693, "slim" 5Z4, "slim" 6AU4, metal shell 6F6, 6J5, 6R7, metal 6SJ7, "slim" 6SN7, metal 6V6, 6X5.*

UltraSonic Rx-25: $29.15 ea.
4 or more: $28.35 ea.

UltraSonic Rx-30

UltraSonic Rx-30 Tube Damper Fits narrow, straight-sided octal tubes and all tubes approximately 1-1/8" to 1-1/4" diameter (28mm to 32mm), including 0A3A (straight-sided), 1266, 12AX3, 12J5/GT, glass 12SJ7, 12SJ7GT, 12SL7/GT, 12SN7/GT, 3CM, 437A, 4P1L, 5691, 5692, 5852, "slim" 5AR4 (G.E., Sovtek/Reflektor, T-9 bulb), 5Y3, 5Y3GA, 5Y3GT, "wide" 5Z4, 6106, 68HC, 6AH4, 6AU4GT, 6AU4GTA, 6AU5, 6AX4GT, 6AX4GTA, 6AX4GTB, 6BL7, 6C5S, 6CJ3, 6D22S, 6DA4/6DA4A, 6DN7, 6EA7, 6EM6, 6EM7, 6EW7, straight-sided 6F6G, 6FD7, 6FM7, 6FY7, 6H4GT, 6J8P, 6K11, 6L6, 6N8P, 6N9P, 6R7GT (glass T-9 bulb),6SF5-GT (glass tube), 6SH7, glass 6SJ7, 6SJ7GT, "slim" 6SL7, 6SN7, 6SN7GT-series (6SN7GT, 6SN7GTA, 6SN7GTB, 6SN7WGT, 6SN7WGTA), 6V6, 6V6GT (GE, Sylvania, Tung-Sol), 6X5G/GT/WGT, 6Y6, 7355, 7591, 7868, 7N7, C3G, C3M, EC8020, "narrow" EL34 (E-H, Mullard, SED "Winged C," Siemens, Svetlana, Telefunken, NOS Tesla, Tung-Sol), EL34/6CA7 (Svetlana), EL34B (Tung-Sol), GZ30, MT8 bulb, PL504, OA3A (straight-sided), T-9 bulb, VT-231.*
UltraSonic Rx-30: $29.36 ea.
4 or more: $28.59 ea.

UltraSonic Rx-35

Fits standard, straight-sided octals and all tubes approximately 1-5/16" to 1-7/16" diameter (33mm to 36mm), including 5AR4 (Amperex, G.E., Japanese "Mullard" copy, Mullard, JJ, Shuguang), "slim" 6CA7 (Tung-Sol), 6H6, standard 6L6/5881, 6L6B, 6L6GT, 6L6WGB, 6SF5 (metal shell), 6V6GT (RCA), 6V6S (JJ), E34LS, ECC33, medium-diameter EL34 (Amperex, Philips, JJ, some Mullards, Valvo), EL34B (Shuguang), GZ34 (GE, JJ, Mullard, Philips, Raytheon, RCA), KT77.*

UltraSonic Rx-35: $29.74 ea.
4 or more: $28.95 ea.

UltraSonic Rx-40

Fits wide and bottle-shaped octals and all tubes approximately 1-1/2" to 1-5/8" diameter (37mm to 44mm), including 0A3 (bottle-shape), 0C3, 0D3, 1626, 19, 27, 30, 37, 3DG4, 520B (near bottom of tube), 5881, "fat-bottle" 5AR4 (Amperex, Mullard, T-11 bulb), 5AW4, straight-sided 5R4-types, straight-sided 5U4 and 5U4-GB (T-12 bulb), 5V3, 5V4, 5Y3GB, 5Y4GA, 5Z4G, 5Z4P, 6080, "slim" 6550, straight-sided 6AS7, 6BY5/G/GA (straight-sided), 6C6, 6C8G, "Big Bottle" 6CA7 (E-H, GE, Sylvania, etc.), "Black Bottle" 6CA7-Z, 6F8G, 6HB5, bottle-shape 6J5 (ST-12 bulb), 6JN6, 6L6GC (E-H, Mazda, JJ, GE, RCA, Sylvania, Tungsol), 6L6WGC, 6LF6, 6P3P, Sophia Electric "bottle" 6SL7 and 6SN7, 7027/A, 7236, 76, 84, 8417, 85, CV3798, "Fat Bottle" EL34 (Big Bottle), EL509, G75/2D, straight-sided GZ32, "slim bottle" GZ37, KT90, OA3 (bottle-shape), OC3, OD3, PL509, QS150/40, VR105, VR75/30, VR75/40.*

UltraSonic Rx-40: $29.98 ea.
4 or more: $29.19 ea.

UltraSonic Rx-50

UltraSonic Rx-50 Tube Damper

For all tubes approximately 1-3/4" to 2-1/8" diameter (45mm to 54mm), including 10Y, 101F, 1610, 2A3 (RCA, Sovtek, Sylvania, Tung-Sol, Brimar), 26, 274B (Western Electric), 307A, 35, 350B, 3A/110A, 3A/110B, 3D21A, 421A, 422A, 45 (RCA, Sylvania, TJ, Tung-Sol), 46 bottle-shape, 572-10, 5998, bulb-shaped 5R4-types, 5R4WGA/B (Tung-Sol), bottle-shape 5U4G, 5V4, 5Y3G (Sylvania), 5Z3, 5Z3P/A, 5Z4G (Brimar), standard and wide 6550 (E-H, GE, Philips, RCA, SED, Svetlana, Sylvania, Tung Sol), 6550A, 6550C, bulb-shape 6AS7, 6B4, 6B4G, 6BY5/G/GA (bottle-shape), 6CA7-Z, 6C33C (upper portion of tube), bulb-shape 6F6G, 6H13, 6H13C, bulb-shape 6L6G, 6N13P, 6Y6G, 71A, 80 bottle-shape, 801/801A, 807, straight-sided 811, 814, C327 ("bulb" 27), CX4, bottle-shaped octals like AZ4, CV181/ECC32, CV181TII (Psvane 6SN7), CV181-Z (Shuguang), CV378 (Mullard), EL156, EL37, bottle-shaped GZ32 (Mullard), GZ33, KT120, KT66, KT88 (E-H, EAT, GEC, Gold Lion/Genalex, JJ/Tesla, SED, Shuguang, Sovtek, Svetlana), PX4, ST-14 bulb, ST-16 bulb, U52.*

UltraSonic Rx-50: $30.29 ea.
4 or more: $29.49 ea.

UltraSonic Rx-55

For jumbo-size tubes 2-3/16" to 2-5/16" diameter (55mm to 59mm), including 101D/101F, narrow 211 (RCA), 211/VT-4C (GE), 2A3 (EML), 2A3-Mesh (EML), 274A, 300B "Balloon" (KR), Svetlana 300B, Takatsuki TA-300B, 45 (EML), 46 globe-shape, large bottle 5Y3GB (smaller Mazda uses UltraSonic 40), 80 globe-shape, "narrow" 805 (RCA, United), 829B, 841, 842, narrow 845 (Amperex, RCA), 845A (Shuguang), 872, GE211, "Big Bottle" GZ37, KT150 (specify size "60" in comments section of order form), SV811-10, ST-17 bulb, T-18 bulb.*

UltraSonic Rx-55: $31.89 ea.
4 or more: $30.99 ea.

UltraSonic Rx-65

With plenty of flex to accomodate a wide range of tube diameters, fits giant tubes from 2-3/8" to 3" diameter (60mm to 76mm), including 101D "tennis ball," 101J, 102B, wide 211 (Sophia, TJ), 274B (EML, Shuguang, Sophia, Valve Art), 2A3-40W (JJ), 2A3 Meshplate (Sophia, TJ), 2A3 Globe Meshplate (Sophia, TJ), 2A3C (Shuguang), 300B (AVVT, E-H, EML, JJ/Tesla, Sovtek, KR, TJ/Full Music, Western Electric), 300B-XLS (EML, KR), Meshplate 300B (EML, Golden Dragon, TJ, Sophia, Shuguang, Valve Art), 300B Globe Meshplate (Sophia, TJ), 32B, Globe 45 (TJ/Full Music/Sophia), 45C, 45N, EML 45-mesh, 50, 520B, EML 5U4G-Mesh & 5Z3-Mesh, 6C33C (wide portion of tube), 803, "wide" 805 (Amperex, Shuguang, TJ), 811A, 813, wide 845 (Sophia, Shuguang metal plate, TJ), 845B (Shuguang), F2A, GM70, PX25, ST-18 bulb, ST-19 bulb, T-20 bulb.*

UltraSonic Rx-65: $32.85 ea.
4 or more: $31.95 ea.

UltraSonic Rx-100

With extra-heavy-gauge stainless steel C-ring and four isolation pads, UltraSonic 100 thoroughly tames microphonics in super-giant tubes 3-1/2" to 4-5/8" diameter (89mm to 118mm), including 833, KR T-1610 (Kronzilla), and tubes using T-36 bulb.

UltraSonic Rx-100: $40.49 ea.
4 or more: $39.89 ea.


Tube diameters and shapes sometimes vary. To estimate your tube diameter, just place a wooden or metal ruler against the side of your tube and "eyeball" the size – if you align your sight in a straight line to one edge of the tube and then in a straight line to the opposite edge, the measured difference in-between will be very close to the tube's actual diameter. Or measure the circumference and divide by pi (3.14).

For tubes that fall in-between UltraSonic sizes, smaller size is the default recommendation (though either size will work). Tube size data indicates "maximum" tube diameter; tubes are often a little smaller than indicated. Titanium C-rings have some flex to them to accommodate variation in bulb diameters and can be bent to somewhat smaller or larger sizes.

Additional information, including bulb sizes, on most tube types and brands can be found here:

[ Frank's Electron Tube Data Sheets ]

inches millimeters 

Changing gear? UltraSonic Rx isolation pads can be slid off one titanium C-ring and onto another. If you need a different size than what you have, spare C-rings are available, so you don't have to buy a whole damping instrument to change sizes. Isolation pads are interchangeable among standard sizes (UltraSonic Rx-Mini thru 50), and amongst heavy-gauge sizes (UltraSonic Rx-55 thru 100). UltraSonic Rx isolation pads achieve a full upgrade to "Rx" for standard UltraSonic Damping Instruments.

 Titanium C-Ring Only (no pads) 
UltraSonic Rx sizes Mini thru 65
$3.95 to $9.98 ea.
(4 or more, one size: 10% off)

UltraSonic Rx Isolation Pad

$7.95 ea.
(12 or more: $7.49 ea.)

90-day no-risk trial. If not satisfied, simply return any item within 90 days for a complete refund of the purchase price.

Lifetime warranty. If anything ever goes wrong, simply return any Damping Instrument to Herbie's Audio Lab and it will be repaired or replaced and returned to you at no cost.

Herbie's Audio Lab offers low prices, high value!

All parts and materials made in USA


Name: Thomas
Message: I want to use these dampers around tubes on Lampizator DAC+Pre-amp with separate PSU (Gen 4 Level 5). Spaces around a pair of 6X5G tubes on the PSU is tight but I think I still could fit a a pair of RX-25s in there.
What happen if there is a part of the C Ring touches/pushes a casing wall? Would vibration from the wall transmit to the tube and defeat the purpose of using the dampers? If I cut a thin strip of delrin/PTFE (maybe about 1- 1.5mm in thickness) and slide it between the C Ring and the metal casing, would that be enough to stop vibration from and to the tubes?


Webmaster's reply: An isolation pad or C-ring touching part of the casing could be beneficial or might be detrimental. To play it safe, direct contact is always best to avoid though, whenever possible. The isolation pads can be moved along the titanium C-ring to avoid contact with any internal parts, and the C-ring is versatile with placement around the tube. If the open portion of the C-ring is facing the wall, you need scarcely any space at all for clearance. Though somewhat tight, you should have plenty of room to keep the tubes and dampers isolated. If an isolation pad or C-ring is touching, a piece of PTFE (but not Delrin) could be beneficial, though a small Herbie's Audio Lab grungebuster Dot would be much better.
Name: Ultrasonic RX
Message: Hi, I've received my Ultrasonic RXs and was wondering about the most beneficial spot on the tube to put them. They are to go on 6SN7's and 7308 tubes which, as you probably know, are the same diameter along the full height. Thnaks, Craig

Webmaster's reply: You should have received an information sheet along with the dampers. Here is a copy/paste from the information sheet: "To install, simply place a damping instrument on the tube and slide it straight down until about 1/3 of the way down from the top. This is the default position, but some experimentation with positioning is sometimes beneficial to achieve optimal results." Precise positioning is usually not really necessary to appreciate a significant reduction of microphonics and improved musicality. Some experimentation can be rewarding, though; optimal location on the tube can vary from one system to another and according to personal taste/preference. You'll usually get the most damping with dampers placed around the middle of the tube, less damping with a damper near the top or very bottom of the tube.
Name: John Hutchinson
Message: I am in the UK and I have bought from you before. Postage charges seem to have rocketed though. I only want some more tube dampers and the postage is nearly the same as the items!

Webmaster's reply: Hi, John. Fortunately, we have been able to keep our product prices low so you still get a great value even with the increased postal costs. Purchasing direct from the manufacturer also keeps you from the cost of dealers or distributors who would double the price of our products. On our shopping cart order form, there is more than one shipping option to choose from.
Name: Peter, Hong Kong
Message: The dampers are really effective in controlling tube micro-phony. My SET amplifier using 6SN7 & 2A3 tubes has never sounded better. Customer service is first rate. One of my best investments in Hi Fi so far!
Name: Steve
Message: How will these go with the McIntosh C1000T 12AX7s perched on the front porch? It is a very tight fit...

Webmaster's reply: Though there's not much space, there's plenty of room for an UltraSonic Rx-9 around each of the 12AX7 tubes. Even more room for UltraSonic SS-9, which hugs just a little closer to the tube.
Name: Calvin
Message: How much clearance between tubes do i need in order to use the dampers for 12ax7 tubes. My mcintosh c2200 preamp is designed with the tubes are too close to each other. Can i use the damper.

Webmaster's reply: There's plenty of room for damping instruments on the tubes in the McIntosh C2200, with room to spare (and you can remove the black X-shaped gizmos on top of each quartet of tubes). UltraSonic SS and Rx damping instruments need only about 1/4" between tubes, even less space between a single pair (the open ends of the C-rings can face each other so that the tubes could be so close together that they actually touch each other and the damping instruments will fit on them).
Name: Marko
Message: I got my first damper yesterday and it appears to have fixed a tube rattle on a Dr. Z Maz-18 that was driving me nuts!
Name: Charles Katz
Message: Placing Rx tube dampers on the rectifier and output tubes of my SET amp worked wonders adding clarity (sibilance disappeared) and opening up the soundstage. Extremely cost effective and highly recommended.
Name: Rosser Clark, Falls Church, VA
Message: I have to admit that I was skeptical about how a few little pieces of silicone pressed against the outer glass could make any audible difference. But I had had such good results with your products before that I thought I would give the dampers a try. I just did a major refurb and modification of my Dynaco SCA-35 -- new boards, new tubes, new power supply caps and diodes, etc. After all that, I listened to it a while, and it sounded great. Then I put the tube dampers on (four Preamp UltraSonics for the preamp tubes and four UltraSonic Rx for the power tubes).

I don't know how you do it, but the dampers made more difference than almost all the other new parts combined. The amp went from sounding good, great even, to sounding absolutely magical. There is a coherence to the sound that I have never experienced in my own system. Everything sounds tied together in a very musical way now. In addition, I'm hearing details in familiar pieces that I've never heard before -- I mean a lot of things that are very easy to hear now, that I never knew were there. The separation and 3D placement is also so much better I can hardly believe it. On top of that, the background is much quieter. The only downside that I thought I heard at first was the high frequency transients sounded a little rolled off -- esp the cymbal attack. But after listening a while, it seemed more like that without the dampers the sound was kind of uncontrolled, and one result of that was an overemphasis or ringing of the highs. There is no way I would go back to the sound before. Anyway, I am so happy with the sound with the dampers that my jaw has been dropping.

Thanks again,

Name: lester
Message: The 300b that I have found to be microphonic is 45 mm at the head and 62 mm at the shoulder. The mica is in the head. Is this where I need the dampers?

Webmaster's reply: Damping instruments are effective at either location; by default, placing a damping instrument around the widest part of the tube is recommended.

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