Responding to the request by Hungryear, a second power supply adds to the Aesthetix's sense of ease and effortlessness. There is an significant increase in both the intensity and headroom, while allowing each individual instrument ( particularly piano ) to show off all their colors and micro dynamics. This change does not appreciably alter the tonal balance, compared to the single supply. It does increase the depth of the soundstage, and with a better sense of location. This increased resolution is not the hyper variety, it does this by it untangling similar sounds, and providing a precise location within the listening space. With both my Io and Callisto running dual power supplies, this is the most dynamic and effortless presentation I have ever had. For this to make sense from a financial standpoint, all the other pieces in the system must be able to resolve this improvement. Regarding the comments by Bud and Rayhall, the 6922 Sovtek would be my first change. For additional midrange and air, try the Siemens 6922 CCa or the Amperex US Military 7308 CEP. If either of these produce too much midrange presence, try the Mullard 6922 (gold pin). Realize, that when you upgrade to one of these higher resolution NOS 6922's you are listening with more intensity to the weaknesses of the remaining (original) tubes. You are judging the replacement, plus all that it exposes downstream. If after changing to the CCa or CEP, you find that there is too much "grit" in the sound, try swapping the 6SN-7 as described in my long post. After that, if you are feeling adventuresome, trade out the first stage 12AX7 tubes (Io only). Note, these 12AX7's are the ones I warned about, get TESTED, ultra noise tubes for this position. My first choice and the most beautiful sound is the Telefunken 12AX7. Other options are the RCA 5751, a US Military version of the 12AX7. The 5751 will alter the tonal balance somewhat, as it is not an exact replacement. There will be a slight loss in gain, with improved signal to noise and lower distortion. Overall, the sound will be a bit more on the dry side. One final suggestion would be the 12AX7 French Mazda. A good sample of this will produce significant improvements in high frequency transparency, especially compared to the Sovtek. However, the Mazda has not been without problems in my experience. The samples I received are not equally reliable or equally low noise. Some will play perfectly for many months while retaining their original "voice" while other samples will develop horrible microphonics and tube noise in as little as a week. This is a situation that could lead to disappointment with the Io, when in fact, the tubes are the culprit. Unfortunately, there must be some risk and experimentation within your own system to determine what is best. All the tubes I have suggested here are expensive to buy right now and will become even more so as time goes by. You should never consider their purchase as a potential mistake. If these tubes do not work in your system now, there will come a time when they will be the perfect answer.
