I purchased a used Alpha from someone via the net. While they sent me the original tubes, the unit arrived with some tubes in it that supposedly were purchased from Audio Research Corporation ( ARC ). Since i also own two different Sigma's ( 16 bit and 24 bit ), i'm pretty familiar with the basic "CAL" sound. Having had them for a while, i have tried a few different tubes in them before. As such, these tubes DO sound very good in this unit. While i don't know if they really came from ARC or not, or if ARC "gain matches" or "hand selects" their tubes, etc... they are Sovtek 12AX7WXT's. I know that Parts Express sells these and i think that they can probably be ordered in matched pairs. Hope this helps... Sean
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