Okay so this isn't really going to be a complete guide but just some impressions, I gave up rolling the 6AS7s so I looked into rolling in some different tubes for the driver side, and my 6SN7s finally arrived. I don't have many tubes with me for input side so I'll just briefly summarize how each tube type sounds.
Bear in mind that the 12BH7, E80CC and 6SN7 draws double the current of the 12AU7 so it would be a good choice to have the Speedball upgrade beforehand!
12AU7/ECC82: Nothing wrong with these but average. the 12AU7 doesn't quite stand out to the rest and is at the bottom of the hierarchy. Exceptions to this bunch are the Tesla ECC802S, Raytheon Windmill 5814A and Telefunken ECC82. From my experience, bigger tube = more air, bigger soundstage. Technicalities wise, The Tesla ECC802S is actually very capable. However, it is only one of the many good value tube amongst the E80CC and 12BH7
Telefunken ECC802S/Bugle Boy 7316: For what they're worth, the Crack is not worthy of these ultra rare tubes.
12BH7: More musical and better micro detail in general. Slightly more air but ever so slightly. Rare Sylvanias or RCAs are very refined and are oozing with micro detail and dynamic range. Brimars or Tung Sol/CBS-Hytron with long curved plates are also good but rarer than RCA and Sylvania, not superior but different tonality. The other 12BH7 such as GE and grey plate RCAs are not as good and you're better off with a premium 12AU7 instead.
Philips Goldpin E80CC/6085 (Also labeled as Valvo, Telefunken, Haltron, Siemens, and early Tungsram): Very musical and full bodied in the mid ranges. Perhaps slightly thin on the highs but a very enjoyable tube with its weighty lows. There's also a foil getter version which exhibits far better dynamic range at a higher premium.
Tungsram Nickel Pins E80CC (Also labeled as Siemens): Very dynamic and linear. My reference "Hifi" tube. Slight bass rolloff but otherwise a fantastic tube. May not be for everyone due to its neutrality but the microdetail and instrument separation is as clear as day. However, this tube is very prone to sibilance on badly recorded tracks (your experience may differ). There is also an extremely rare silver plate and silver foil-D getter version of the Tungsram but I've never had my hands on one as they are extremely rare.
6SN7: Basically something like the 12BH7 BUT comparatively more "vintage" in musicality. Perhaps not superior in sonics and technicalities but the music becomes so involving that it's a far better listen than the others. Sylvania VT231 or Tung Sol Mouse Ears are a good premium.
Sylvania 6SN7W, GEC/Marconi/Brimar CV1988/B65, Tung Sol VT-231/6SN7 Round Plates: The premium tubes of the 6SN7 family throws in technicalities, air and transparency to the mix. Far more dynamic and detailed. However, not worth throwing into the Crack. Regardless of which of these tubes mentioned at $150+ per piece the Crack will not do it justice. (It probably would if you had some good headphones like the HD800) but otherwise, I think to use this in the Crack would be an over-expenditure.
« Last Edit: April 04, 2013, 08:30:59 PM by Nick Tam »
Bottlehead Crack
Source: Fostex HP-A4
Cans: Sennheiser HD700
Sylvania GB6080 + Sylvania VT-231
