I have been a user of Alan Maher Designs products for a few years now. My collection includes 5 of the original Power Enhancer series parallel filters, a custom Power Enhancer, Reference Power Center V2, and now the Reference II. These products replaced a Running Springs Haley, BPT Pure Power Center (non-filtering model, customized with Litz wiring and 3 Oyaide SWO-GX duplex outlets), and 3 PS Audio Noise Harvesters that were previously used in my system.
In addition, I have also tried BPT and Equitech balanced power conditioners, as well as the Exact Power EP-15A in my system. Of these, the Running Springs Haley came closest to the performance of my AMD set-up.
Similar to my experience with other Alan Maher passive filtration products a significant break in time to allow the Reference II to "charge" and tune the circuit was required before results could be evaluated. Typically the break in period is 20 - 30 days. In addition, placement on the circuit can also influence the performance of the Reference II. Having had experience with other AMD passive filtration products I have gotten pretty adept at how to place these devices. Other users may need to spot test a bit more to find the optimal location. In my home I placed the Reference II on the circuit my audio gear is plugged into. The circuit controls 3 duplex outlets (and a couple light/ceiling fan switches). Two of the outlets are used for my audio gear. Nothing is plugged into the third outlet on the circuit. I decided to plug the Reference II into the same duplex outlet that my Furutech ETP-60 is plugged into. The ETP-60 only has my amps plugged into it.
Upon initial installation and listening two things were immediately evident. The first was the reduced noise floor and the second was the increased spaciousness and 3D sound stage. These factors remained very consistent through out the break in process. However, each week provided various results as it relates to tonality and balance. The first week found the system sounding fairly smooth overall. While the musical test selections sounded very good, they lacked the usual dynamics. Bass was sharp with snap and vibrancy, but the mid range was a bit dry and the upper frequencies sounded rolled off.
Week two was the torture test as the system went through significant mood swings. Bass was the most significantly affected at times sounding mushy, bloated, and even "disappearing" altogether. Mid-bass was most affected by the latter trait. While the high end turned bright on occasion, it smoothed out and snapped into focus sooner than the bass and mid-bass.
Week three saw the entire system snap together to arrive at the final sonic signature. In the end in addition to the previous noise floor and spatial benefits, there was increased extension at the frequency extremes, especially bass definition, and the mid-range was slightly warmer. Overall the system changes helped produce a very real and focused presentation, especially with recordings that featured vocals.
Musical test recordings used to evaluate the changes included:
Brian Bromberg - Wood: I use this recording frequently at audiophile shows and in home testing. Specifically, track 3 which is a bass solo of the Beatles Come Together. Adding the Reference II to the system created a more authoratative bass with increased detail that was very apparent in the fretting.
Todd Garfinkle - Further Observations. I generally like to listen to this entire CD when using it for testing purposes. This is a one point recording featuring a trio comprised of piano, bass, and percussion. As such the sound of the CD already possessed exceptional stereo imaging. With the Reference II added to the system space between the players was well defined and instruments were more stable and better focused within the sound stage. At the beginning of the song, After.....Before, the siren was crisp, clear, and dead focused on center. Additionally I noted that the cymbals on all tracks were a tad warmer with nice decay.
Tsuyoshi Yamamoto Trio - Girl Talk: Another trio featuring piano, bass, and drums. Again, increased spaciousness between the players. The piano specifically appeared to move forward within the sound stage and went wider than prior to the Reference II being added to the system. Track 3 features an instrumental rendition of Gone with the Wind with a bass solo that now produced more snap and vibrations of the strings, as well as deeper extension.
Rob Wasserman - Duets: Deciding to hear the results on vocals I went straight to the version of Gone with the Wind on this CD featuring Dan Hicks on vocals. The addition of the Reference II to the system created a larger yet more focused image of the singer. The vocals were clear and more life like. The bass again had more snap and authority to it. The separation of lead vocal and instrument was larger, and as additional background vocals appeared on the track, they were distinctly separated from the lead vocal and instrument as well.
Yo Yo Ma - Abrigado Brazil Live. This CD is a good system test for me. With the increased number of instruments my small listening room has always presented imaging problems with this CD, most noticeably some left channel congestion. Adding the Reference II to the system did not eradicate the problem, but it did alleviate it as again, there was more space between the instruments. Overall the bass, previously a bit lacking and seemingly out of balance with the rest of the instruments, now was very present and acted like it felt right at home in the recording. The increased air provided by the Reference II was most apparent on this CD.
Philip Glass - The Low Symphony: Another challenging recording for my system, similar spatial improvements as in previous tests could be heard. Additionally, the strings which previously appeared to be a bit dry, were now more vibrant and the increased sound stage layering resulting from the addition of the Reference II to the system was more noticeable on this CD.
I would encourage anyone interested in trying an inexpensive tweak to look into the Reference II. While one should give you a good idea of the improvements that can be had, as my experience from using the original Power Enhancers taught me, multiple properly placed Reference II's will generally yield even better results. AMD does offer a trial period, subject to a 15% restocking fee on returns. Also, while this review focused on how the Reference II performed in my 2-channel audio system, the results on my 26" Sony LCD panel were not subtle and even more noticeable than with audio. The changes included an increased level of blackness and sharpness, as well as deeper color saturation. So the product has applications for HT and video users as well.
Associated Equipment for this Review:
Amplifier: VAC Auricle Musicblocs (70 watts)
Preamplifier: Jeff Rowland Design Group Capri
Sources: CEC TL-51X transport/LessLoss DAC 2004 MkII
Speakers: Audiokinesis Jazz Modules (92db)
Cables/Interconnects: Interconnects/Speaker - Music Note (digital) Magnan Type Vi (source/preamp), Grover Huffman SC (speaker), Mogami Gold Neglex (preamp/amp). All interconnect cables except digital (XLR-to-RCA) balanced XLR. Power Cables - Tel Wire (preamp, transport, DAC), Fusion Audio Predator (amps).
Music Used: Brian Bromberg - Wood, Todd Garfinkle - Further Attempts, Tsuyoshi Yamamoto Trio - Girl Talk, Rob Wasserman - Duets, Yo Yo Ma - Abrigado Brazil Live, Philip Glass - Low Symphony.
