Stein Music Q5 Quantum Filter



davecaplan.jpgHolger Stein recently sent me a pair of his Q5 Quantum Organizers to evaluate. When I opened the package and held one in my hand It looked exactly like a generic audiophile male plug head that comes attached to high end power cords. I was immediately skeptical that it could impact my audio system in any meaningful way. 


The instructions told me to plug one of the Q5s into my power condi­tioner and the other one anywhere else in my listening room. I have to say my experience with some other Stein products like the Harmonizers or Blue Suns (right) haven’t disappointed (read more about them and Holger Stein here).


Psychologically, I wasn’t motivated to try the Q5’s right away because I guess I didn’t believe some­thing as small as a plug head could do very much. The Q5 sat on my desk for about a week before I finally decided to put them to the test. I put on an Art Blakey ’63 classic “Caravan,” which still remains one of my favorites. I listened to the title track Caravan, a few times, then I plugged the Q5 into my Acoustic Revive AC conditioner and repeated the song once again. What I heard put a smile on my face. This little plug was definitely creating a musical improvement to my audio system that was beyond my expectations and I hadn’t even burned it in.

caravan.jpgFor example, the drum solo on Caravan had increased dynamics; the rim shots had more attack and more focus. It definitely took my system in a more musical and positive direction. It sounded slightly more alive and less flat which gave the saxophone more accurate tonal colors. After a short listening session, I unplugged the Q5 and the sound suffered a noticeable degrade. Next, I put on Diana Krall “Live in Paris,” and again I got the same improvement. Her voice was clearer and a little more dimensional. The piano was also more natural with richer harmonics. By the next day the Q5 improved my system even more.

Holger Stein explained that the Stein Q5 works differently than a conventional parallel filter. These filters usually suffer dielectric losses, which can create a suck out of energy in the music. They have a ten­dency to smooth the tone, to mask the line noise and cause a loss of some micro detail and harmonics. This doesn’t happen with the Q5s. Stein further explained that their goal is not adding another component to compensate for faults that have happened somewhere else: the Q5 is designed with a very high Q which only gives an attenuation of about 3dB at 10MHz. This means the losses are extremely small as the Q5 incorporates advanced micro circuitry that combine their quantum and crystal technology and reduces audible distortions in your AC power-line and allows the electricity to flow with less resistance.

Stein recommends using a pair of Q5s so I plugged the second one into the back of my listening room and again there was a further improvement. The Q5 Plug was acting like to turbocharger on my the AC line coming into the house. After burning in the two Q5s for a week there was still a little further improvement.

CantateDomino.jpgNow it was time to test the Q5s on my friends system which consists of panel speakers and high end separates and an assortment of noise reducing devices like Shakti Stones and Onlines, Bybee Speaker Bullets, Acoustic Revive R77s, and a PS Audio Power conditioner. I repeated the tests exactly as I did on my system. We first listened to the Cantata Domino CD, cut 11. Then I put 1 Stein Q5 plug into his con­ditioner. We both heard a significant improvement in the sound; what I would describe as a more cohesive presentation overall. Richer harmonics and greater dimensionality appeared and created a noticeably more engaging sound.

We put in the second Q5 in a wall outlet and heard a further improvement as depth and 3-D layering were more clearly revealed. My friends wife is a lover of classical music and when she sat down for our demo, after a few minutes of listening to the Q5s in their system, the first words out of her mouth were “you’re not taking those home are you?” There’s no question that the Q5s increased the musical enjoyment in our 2 different audio systems. Holger Stein, once again, has created a small, easy to use, highly effective noise reducing device that just works. You can view it as a tweek or consider it a powerful tool in the quest to reduce electronic grunge. Highly recommended!


 david caplan


Stein Q5 Quantum Mains Filter


Price: $598.00 USA at Tweek Geek (
Stein Music Website: 


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