12BH7 may work in that circuit, it is designed with similar parameters as 12AU7 and 12AT7. I used 12BH7 in my Air Tight ATM3's and got a huge upgrade.
If you want to play it safe, score some Telefunken 12AT7 off EBAY, plug, play and be prepared for a huge sonic improvement with no risk or downside.
If you want to play it safe, score some Telefunken 12AT7 off EBAY, plug, play and be prepared for a huge sonic improvement with no risk or downside.