While searching the various audio forums, I came across a company called Herbie's Audio Lab, owned by Steve Herbelin, that sells various inexpensive accessories to increase the performance of your AV system. Because I am now running tube buffers, I wanted to see if using his HAL-O tube dampers would make any difference. It is a C shaped ring with several elastomers on this ring that rolls onto the vacuum tube to reduce "microphonics". I am testing his least expensive HAL-O which is made of Teflon which according to Steve Herbelin, provides a neutral sound. He also sells these HAL-Os in various sizes and uses different materials for a different sound. According to his site, many vacuum tubes have microphonics that can smear the sound and reduce the detail of information being passed to your speakers. Associate microphonics as the vibrations or "ringing" that glass vacuum tubes can produce and be picked up and transmitted which can smear the sound in your AV system. Reducing or eliminating these microphonics in theory increases the level of detail, reduces the harshness and provides a better overall balanced presentation to the music. I started off thinking my AV system sounded just fine and didn't think I had any microphonic issues but as I share my experience using various recordings, I was wrong.

Installation:
It was quite easy, the HAL-O slips on very easily onto the vacuum tubes. The Herbie's Audio Lab web site suggests placing the tube damper in the upper half of the tube. You can experiment and try different locations to see what works best for your system.

Sound:
First, I started with my current reference CD, Norah Jones', "Not Too Late", and used the second track, "Sinkin Soon". This track has a complex set of instruments placed throughout the soundstage, including piano, banjo, trombone, bass and drum instruments. Once I placed the HAL-O tube dampers onto my Musical Fidelity x10v3 tube buffer, I immediately noticed that the instruments had greater definition in space with a reduction of harshness I didn't realize existed. Norah's voice came through even more true-to-life while the overall presentation had greater bass impact and clearer highs. Attack and decay of each instrument was more precise giving a truer-to-life sound to each. It's as if someone turned up the sharpness control one or two turns, using a video analogy.

Next, I used the SACD of Yo-Yo Ma's, "Silk Road Journeys", and played the second track, "Byambasuren Sharav: Legend of Herlen", this track has a female voice in the center channel that can be quite gritty and shrilly but at the same time have a recessed reverberate sound due to the large room he used to record it with. Because this recording is in 5.1 surround, I also installed a HAL-O onto my Yaqin tube buffer which I also reviewed here: http://www.epinions.com/content_312424107652. Immediately, the female voice still had the dynamic grittiness but the shrill I thought originally was in reality microphonics smearing this shrill and mixing in harshness that I had in my system. This female voice was much easier to listen to and presented a more reverberate and wider sound giving you a sense the recording room was even larger. Again, overall presentation was more balanced and detailed. Yo-Yo Ma's cello sounded more realistic with a more defined attack and decay when his bow hit the cello's strings. Again, the sharpness control was turned up again.

Last up was the DVD-A of The Beatles, "Love" and I played the fourth track, "Eleanor Rigby, Julia (Transition)". Again the overall presentation was more balanced and precise. With the HAL-O in place individual instruments played more life-like and was easier to place around you. The cello out of the right front speaker sounded like it was in the room as well as the violin out of the left front speaker. Paul McCartney's voice out of the center channel sounded very natural and had more air and reverberation around his voice than without the HAL-O in place. The HAL-O seem to add precision, attack and decay throughout this complex track. Again, without, everything seemed smeared, less defined and less life-like.

Conclusions:
Overall, I was pleased with the positive results that the HAL-O tube damper did for both my Musical Fidelity and Yaqin Tube Buffers. The HAL-O in summary provided a better overall balanced presentation with greater bass and treble definition. If you are running vacuum tubes in your AV system, you need to try Herbie's Audio Lab HAL-O. I think you will be pleased with the results. And even if you don't think the HAL-O tube damper made any difference in your AV system, Herbie's Audio Lab has a generous return policy that you will see below.

Features:
Steve Herbelin sells his HAL-Os in various sizes for small to large tubes and different materials for various sound needs.

Warranty and Return Policy:
Lifetime warranty with a 90-day return policy if you don't like the product.

Customer Support:
Excellent, because the person that answers the phone is Steve Herbelin, owner of Herbies Audio Lab. He definitely can answer any questions you have about the HAL-Os.

Pricing and Web Site:
Check the web site for specific pricing based on size and materials used but the range is from $8.95-$45.95 for each HAL-O. My review was based on the least expensive HAL-O.
Web Site: http://herbiesaudiolab.net

Associated Test Equipment:
Musical Fidelity x10v3 Tube Buffer
Yaqin Tube Buffer
Mitsubishi WD-52725 52" DLP HDTV
Parasound HCA-1205A 5-Channel Amp
Parasound AVC-1800 Pre-amp
Magnepan IIIa Front Main Speakers
Eminent Technology LFT-XII center channel speaker
Magnepan IIIa Rear Surround Speakers
Velodyne HGS-12 Series II subwoofer
Sony CDP-CX240 CD Player
Oppo Digital DV-970HD Universal DVD Player
Pro-Ject 1.2 Turntable with Sumiko Pearl Cartridge
Channel Island Audio VDA-2 DAC and VAC-1 Power Supply
Synergistic Research Interconnects and Speaker Cables
Signal Cable Power Cords
PS Audio Prelude, Plus SC, Statement Power Cords

Recommended: Yes