I have AKG k612 headphones.
I bought the Aune T1 for about $100 US and some tubes seem to be about that much which I can't afford. At the moment I'm browsing different sites trying to find a good tube for below $40 US that also ships to NZ. Seems a wee bit tricky to find
6922/E88CC tubes = longer life, a bit more refined than 6DJ8/ECC88 tubes:
Telefunken tube (fast, ss sounding, natural tube euphonics, not much warmth):
http://www.ebay.com.au/itm/Telefunken-E88CC-6922-6DJ8-Vacuum-Tube-/131552290719?pt=LH_DefaultDomain_0&hash=item1ea120a79f
Amperex tube (US made, see post above):
http://www.ebay.com.au/itm/MATCHED-PLATE-AMPEREX-6922-E88CC-USED-TUBE-TESTED-B-K-707-103-104-/281630662518?pt=LH_DefaultDomain_2&hash=item41927edf76
I think this is also US made, can't tell:
http://www.ebay.com.au/itm/NOS-Amperex-6922-E88CC-Vintage-Tube-Gold-Pins-O-Getter-/151737045179?pt=LH_DefaultDomain_0&hash=item23543b90bb
Brimar CV2492 tube (Made in the UK, similar to the Holland 6922's):
http://www.ebay.com.au/itm/1-X-CV2492-6922-BRIMAR-TUBES-NOS-TUBES-PRICE-IS-FOR-1-PC-CRYOTREATED-/191294020982?pt=LH_DefaultDomain_0&hash=item2c8a031d76
6DJ8/ECC88 = less life but cheaper:
6DJ8, Philips/Amperex Holland made:
http://www.ebay.com.au/itm/Vintage-Amperex-6DJ8-ECC88-Holland-TUBE-10-200-8750-/400940505443?pt=LH_DefaultDomain_0&hash=item5d59ea9963
6DJ8, Philips/Amperex 1965 Holland made (A good deal, I'd recommend this tube):
http://www.ebay.com.au/itm/Vintage-Amperex-Holland-Bugle-Boy-white-text-ECC88-6DJ8-preamp-tube-tested-65-/351293745274?pt=LH_DefaultDomain_0&hash=item51cabd287a
6DJ8, Philips/Amperex Holland (Also a decent deal):
http://www.ebay.com.au/itm/ECC88-6DJ8-Made-In-Holland-/111717617410?pt=LH_DefaultDomain_0&hash=item1a02e38f02
More results:
http://www.ebay.com.au/sch/i.html?_odkw=6922+tube&LH_PrefLoc=2&_sop=2&LH_BIN=1&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR1.TRC0.A0.H0.X6dj8+holland.TRS0&_nkw=6dj8+holland&_sacat=0