Customer Comments:
Another winner! The Reference II Filter has elegantly lifted my system to an exciting new level of audio finesse. The difference is not subtle, but quite astonishing with the use of only one filter. The system sound is smoother, sweeter, and warmer, with a relaxed, unstrained quality even at higher volumes. The music sounds more natural, tonally neutral and melodic. The timing is more accurate and coherent allowing more inner detail and inflection to be heard. The power band of the frequency range is more evenly balanced. The pushes on forte vocals are smoother and better controlled, not getting glary, hard or sibilant. The dynamics sound more natural. There is more control in the top end with less tizz and noise. The upper mids and highs are coherent and easy to listen to. Overall, there is more body and a lower noise floor. The bass is fuller and weightier. Alan, kudos!
Will Chow (Vancouver, BC)
Hi Alan,
After moving the Reference II to many locations here's what I have:
S/AC on dedicated audio wall outlet
Reference II on circuit with dehumidifier
PE II on outlet with HT equip
After about 3 hours, the Reference II had the following effects -
There was more delicacy in the highs and an air around instruments and voices that had not been there. More dimension, depth if you will. The texture in the midrange was more involving - no edginess, smoother. The change I noticed in the bass was more control, slightly tighter.
Adding the Quantum filter you sent to my audio power strip -
The Quantum Filter had a totally amazing effect on the overall sound of the system. Everything was more 3 dimensional, rounder, smoother and deeper. The highs would float, absolutely no edginess, no midrange glare (not that there was but this filter removed what gave that impression). Midrange texture had more feel to it, more dimension. And the bass - WOW, deeper, smoother, more punch.
It is phenomenal that your 'box of rocks' can accomplish what they do. This is a great business. It never ceases to amaze me how paying attention to details pays off. Your vision, determination and contributions to audio are returned to you in spades by the enthusiasm, comments, forum participation and success you enjoy each and every day!
Keep up the great work!
Steve Hallick
The Ref II has been with me for a month and a half, and I find it very musical to my ear. To be more accurate, I feel that my audio/video components are very happy with the Ref II.
At first, I struggled with finding the optimal placement: what AC outlet should I plug in the Ref II for best results? I tried several locations: the outlet next to my main (where a PE V Pro Custom sits), the next room where I run computer/hard drives/router/DSL modem and various places around the room and around the house. So far, I prefer the initial instinct: Unplug and move existing Ref I to an outlet where a PE II had been sitting, plug in the Ref II, move the PE II to the adjacent bathroom. This configuration gives my system the warmth I needed and lowest distortion leading to longer more relaxing listening sessions.
The setup in my room is half battery, half AC powered. Optima Redtops are feeding juice to RWA SB2 (xport) and Altman's DAC, Single Power MPX3 and Audio Sector Patek SE are plugged in AM's power strip which in turn plugged in PE V Pro Custom.
For the last month and a half I have been listening to (and took notes of) mostly jazz and pop vocals, which I think are the forte of my single driver speakers - Bob Brines' FTA-2000s. Classical orchestras, new age, operatic voices will be auditioned and reported later in a Part II.
Now, onto the sound. Only a few hours in my room, the Ref II already made an immediate and noticeable difference. The music suddenly became warmer, edges around sibilant voices rounder, less harsh. Bass line got more tuneful. But beside the added warmth (pleasantly so, not the overly warmth associated with lesser tube gear) it's hard to pinpoint exactly where the improvements are. Most if not every ingredients of music seems to come together, like the various singers of a choir hold their voices together, for the better and rendering a more organic performance.
There had been a weakness in my system that, even after installation of many PEs (PE I, II, II, IV, V) and Ref I's in the house, disallowed me to enjoy male vocals. There was always some glare in male voices (Il Divo, Josh Groban, Nat King Cole tracks). But after the Ref II came and stayed with me for a month, I found myself listening to (and enjoying) male vocals more often that I used to. More so, female vocals are sounding better and better, not other way around.
Whether I play tracks of Diana Krall, Holy Cole Trio, Patricia Barber, Stacey Kent, Norah Jones, Sheila Chandra, Rene Olstead, Jacqui Naylor or Il Divo (Carlos, Urs, Sebatien, and David), Josh Groban, Nat King Cole, the performers consistently sing in my room with warm, palpality and intimacy that I ever wished for. Accompanying instruments (bass, guitar, percussions, sax) also play with colorful texture and good stereo separation. Voices are presented as a huge body, rich in tonality, swift in speed, detailed yet not too much sibilance. Makes me wonder if and how adding a few more Ref II's would further expand the big yet warmly intimate performance. And yes, the background is blacker. Quieter, lower distortion, that is.
Video, as a no surprise with Alan Maher's products by now, has improved as well. Color gets a shade more vivid, black get blacker, there are less picture distortions. Pictures are getting easier to look at, sounds more listenable, more pleasant.
A side note: A music lover friend stopped by, had lunch with me, and we both had a listen before driving off to a local audio store for an auditioning (he owns a pair of B&W 804s and is eyeballing a McIntosh MC-275 calssic tube amp). At home we listened to a few "usual suspects": Diana Krall's I Miss You So Much, King Buiett Trio's Gee Baby Ain't I Good To You, Nat King Cole's Autumn Leaves. In the dealer's sound room we listened to a pair of B&W 805s first, then the B&W 802s - oh boy, do they look awesome! The 802s were driven by an MC-275, music source was a McIntosh MS750 Music Server. I was most impressed by the playing of The Fairfield Four recording. The huge, fat, warm bass voice sits towards and hangs above the left speaker, while other three accompanying voices sing toward the right side, much smaller in image size. When I got to hear the song I Miss You So Much (Diana Krall), her voice tends to be placed in the center but far back behind the two speakers. Overall, the presentation at the sound room was somehow cooler than that in my room, and I think the Ref II contributes to it. Otherwise, I didn't feel losing much of high fidelity and more importantly musicality after coming back to my room and listened once again to similar materials.
I like the Ref II for its effectiveness, high performance per dollar value, shorter break-in time, and its share of audio/video tuning capability among those products of Alan Maher.
Paul Bui
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.
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 throughout 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 authoritative 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 lifelike. 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.
Anthony Chipelo
Having played around with Alan’s standard power enhancers and his PE V Pro Custom, I thought I was fairly familiar with what to expect when inserting one of his devices. Normally, one expects a period of time during which the sound is noticeably worse and one wonders whether they have made the right choice in inserting the filter or not. With the PE V Pro, this was a very long period of time, before the sound settled and changed for the better. I recently had the chance to try out Alan’s newest offering, the Reference II. Being quite happy with the sound of my system now that the PE V Pro had settled, I hesitated plugging in the Ref II, fearing that period during which the sound degraded. Much to my delight, I found the Ref II to be a completely different beast altogether. The PE Pro took a lot of faith to keep it plugged in after hearing what the system sounded like for the first week or so after its installation. The Ref II, once I had picked the right circuit, happily settled in within a couple of days, never really causing that same period of bad sound to get the good sound afterwards. Rather, things started sounding better right from the get go. The changes with this filter were a bit more subtle than those with the PEV Pro, but are significant, nonetheless, since they occur in the important area of naturalness of the sound being reproduced. Instruments have more “body” and the sound is, for lack of a better word, more “ripe” sounding. This is especially apparent with string instruments and low brass. More of the lower harmonics that give weight and body to the instruments seem to be present with the Ref II in place. In the case of the cello, the sound doesn’t come from a flat plane anymore, but seems to come from a resonating 3-dimensional wooden instrument. These changes make listening infinitely more pleasurable and lifelike. Overall, I am thrilled with the improvements wrought by adding the Ref II filter to my system (system here meaning the electrical system of my house, since at Alan’s advice, the Ref II is installed in a non-audio circuit). Even after being in the circuit for 2 weeks, things continue improving a bit each day, with the sound becoming more and more lifelike. Every CD sounds better and much more emotionally involving than before the Ref II. Even CD’s I would cringe to listen to before are now quite enjoyable, with the Ref II having further reduced that upper frequency haze that can plague digital playback, especially when the CDs are poorly recorded. The Ref II is a clear winner, and at the price Alan is asking, it’s nothing short of a steal!!
Chris Porada
Update: I do have one very informative experience from the other day, however, which I think speaks volumes about what the Ref II can do for one's system. The other evening, I was listening to Janos Starker playing the Bach suites for Cello. I had my eyes closed and was marveling at the unbelievable dimensionality and timbral improvements that the Ref II had wrought from my system. It was like he was sitting in our family room playing. You could actually visualize the cello, the chair, and Starker all in 3-D space. It was unlike anything I had ever experienced from stereo sound. Unfortunately, there was this annoying heavy breathing coming from the space in front of me which I knew had to be one of our dogs who always joins me for my listening sessions and usually falls asleep. I tried to ignore it, but finally huffed and opened my eyes to see if I could get the dog to move elsewhere and stop making so much noise. When I opened my eyes, I realized the dog was nowhere to be seen. The heavy breathing I was hearing was that of Janos Starker! Upon closer listening, I noted the breathing was perfectly synced with the musical phrases. That's the first time I've ever been fooled by my own stereo system into thinking a sound was coming from the inhabitants of the room rather than the stereo!
All I can say is WOW! I haven't had this much fun listening to music since when I was a kid and didn't know anything about good quality sound. I could just get completely caught up in the music and forget about the stereo. Thanks Alan for making such phenomenal products.
Chris Porada
In my time I've tried quite a few power filters including 1:1 Transformers, ferrites, chokes, commercial capacitor networks, DIY resistor-capacitor networks, Bybee filters and numerous commercial filtration strips. From all these trials a clear pattern has emerged - active, current limiting filtration such as generic surge suppressor strips is almost always detrimental to the sound of audio equipment. 1:1 Transformers are great for front ends like CD players and digital equipment, but terrible for pre-amps and amps. RF suppressors like ferrite clamps on AC power are always detrimental to the sound of audio devices, even when placed on only the earth wire. However they do have a place on video equipment and on non-AV equipment on located on different circuits to the audio system. Usually the very mechanism used for filtering the power has an audible side effect which far outweighs any filtering effect.
Devices that I have found which are generally positive for audio systems are 'passive' filters. These don't suppress current surges, but rather use capacitor networks whose most basic function is to shunt high frequency noise away from the active lead of the AC power supply to stop it from entering your equipment. This high frequency noise or Radio Frequency Interference (RFI) is becoming worse in its prevalence due to computer use, wireless networks and radio communications. Even worse is the prevalence of 'switching power supplies' found in almost all household appliances? All of these sources radiate RFI directly though the power line, or through the air and are picked up by power cables just like antennae. Some components are not noticeably affected by this noise, but others, such as digital audio players, preamps, phono preamps etc can be quite profoundly affected and then amplified through the audio reproduction chain. The audible results are not usually directly noticeable as white noise or gross signal breakup, but fatiguing, edgy treble or an unnatural murkiness to the sound. Often you can't consciously hear the background noise, until it is taken away, making backgrounds sound 'blacker' and the audible signal is 'brought into focus' and made clearer.
After trying my own hand at a couple of DIY passive filters, I thought I would try some of the Alan Maher Designs "Power Enhancer" filters. I liked what I heard, which was a cleaner purer sound where I could hear more resolution in the midrange and higher frequencies. It was clearly better than my DIY attempts and other commercial passive filters I have tried. Since then I have tried almost the entire range of "Power Enhancer" filters, and now the subject of this review, the "Reference II" filter.
Sound wise the Reference II seems to combine the sound qualities of the Power Enhancer I, III and IV and roll them up in a single general product - highs and midrange are cleaner and bass is more defined. It seems as though I can 'see into' and enjoy the midrange more. The Reference II also seems more neutral tonally compared to other Power Enhancers. As with all of these passive filters the Reference II seems to interact with different components in different ways, and synergizes with some components more than others. So trial and error is highly recommended which for which component it works with best and where on your audio circuit find its most effective location. In my system the Reference IIs have settled into the adjoining socket to each of the duplexes feeding each of my Channel Islands monoblock power amplifiers. I cycled through this configuration without any filter and also with other filters in their place. The result was that the Reference IIs always sounded better than anything else in this position.
Some other information about the Reference II filters. In my experience the effect the filter has on the sound does not stabilize until they are 'burned-in' which takes about 5 weeks. So don't judge them until they have been in circuit for a while. These filters come packaged in 'wall-wart' style cases with a USA plug without a ground pin. The way they plug in is very important, in fact integral to the way they function, and must be positioned the correct way around, so that the active and neutral prong goes into the correct hole in the socket. This usually means that the hanging end of the case must face ground, or be oriented towards the where the ground pin in the socket is. They should not be plugged in 'upside down'. International users must use a reasonable quality plug adapter which preserves absolute polarity. Note that European and Australian plugs swap active and neutral positions so if there is a one to one correspondence in your adapter plug then the Reference II will need to be plugged into the adapter upside down compared to a USA socket, in order to preserve the AC polarity. Since the filter is a 'wall-wart' with quite wide case, users may also find that this becomes cramped or physically impossible to plug it into some power boards or double duplex sockets. In this case a short IEC power cable ('jug-plug') can be used with a PC burn in adapter to plug the filter into tight spots. Also note that the Reference II uses X-rated capacitors which are safety compliant for 110-240V applications.
In conclusion, my opinion is that the Reference II is the best low cost passive filter product on the market. It is the culmination of many iterations of passive filter design based on empirical testing of how the unit sounds and not just how it measures. I recommend it as great standalone filter or for use in concert with other power treatment devices.
Carl Braga