I started with the USB Isolator. My Antipodes S40 output into it, the isolator did its thing then fed my Ideon Audio EOS DAC, both connections via USB. The fancy strip on the front of the Sigma Wave only lights when the device is synced. I was sceptical about how much of an impact the isolator would have on my chain. Experience told me that any change in the playback chain has an effect but whether this might represent an improvement was another matter entirely. But I heard quite clearly that yes, it did have an audibly positive influence on my system. Immediately after the Sigma Wave connected, the soundstage became a little wider with a bit more space between performers. The spatial spread expanded and grew more distinct. Nothing serious but clearly noticed. When I removed the Ideon, width decreased again. Interestingly, subjective stage distance or depth gradations were less affected.

My playback was neither more warm nor sober but the Sigma Wave accentuated the little extra kick which my EOS DAC gives the lowest bass which I really enjoy. This wasn't dramatic but enough that some recordings which tend to excess at the bottom ended up too "fat" riding the Sigma Wave. "No Roots" from Alice Merton's album Mint was one such case. Denon's digital master of Kodo vs Yosuke Yamashita's 1986 Live on the other hand is very carefully controlled in the lower ranges. You can tell that it's from the early days of digital. Here the Sigma Wave's small low-bass boost was certainly welcome. Sonic grip was an audible leap forward. Each tone appeared more clean, defined and precise. This is often described by the proverbial blacker background which in the case of a television picture means that the deeper the black values on screen, the better the colours especially contrast. The same is true for cinema. The less light scatters from illuminated emergency exits next to the screen, the clearer and more contrasting the images. The Ideon Audio Sigma Wave USB Isolator was similar in an acoustic sense. The number of details did not increase but each one isolated better. Timbres did not become more colourful but cleaner so that images might separate better from one another.

During one of my sessions, I got stuck on tango where there's hardly any way around Carlos Gardel or Astor Piazzolla. Alas, the only recordings of Gardel I know are historic and really bad. Many of them suffer analogue tape hiss. A system with good resolution helps because it makes it easier for the ear to identify the noise as a separate element. If we listen a little longer, a kind of mental retouch has the ears block out the noise and concentrate on the voice. At some point we no longer clock the noise to instead feel amazed by the vocal expressivity which a really old recording can still convey in 2025. This worked very well with the Sigma Wave. To appreciate it, take just about any available edit of "Por una cabeza". What fascinates me about Piazzolla are his often complex arrangements. Just listen to "Libertango" on Adios Nonino, recorded with the master himself on the bandoneon. The melodic lines of the individual instruments are easier to understand the more clearly we can identify them based on timbres. The Sigma Wave simply made it easier for me to follow the complex weave.

I admit to feeling surprised and a little annoyed that the influence of the Ideon was so clear because now I wondered whether I must invest the next 6'000 euros in my system. Sometimes the reviewer's job is a pain. If I'm honest, I really hoped that the influence of the Alpha Wave LAN Optimizer wouldn't be quite so clear. First I wanted to know what it would do on its own. So I removed the Sigma Wave and patched in the Alpha Wave in front of my Antipodes S40 server. Even though the Antipodes now connected to the LAN via USB, it behaved no different. Unfortunately the addition of the Alpha Wave was clearly audible. It didn't make the sound any warmer or cooler but I immediately noticed that bass control had taken a really impressive step forward. I just wrote that "No Roots" with the USB Isolator tipped into bass that was too rich but the Alpha Wave kept a firm rein. Overall the bass seemed a touch less opulent but gained a degree of depth, contour and control I would not have thought possible. True, ultimately these were still nuances but I found them surprisingly decisive. I rarely had so much fun with bass so let the Alpha Wave blast me unashamedly. Regardless of whether electronic or acoustic music, I could only love the low tones which my EOS DAC with the Alpha Wave peeled out from the data.