Ericteh, Are the Telefunkens you are using current production or NOS?
Upscale Audio recently purchased a large quantity of brand new, never used NOS NIB (new in box) Telefunken E88CCs and is selling them for a very good price. I would strongly recommend that you try these in a preamp of the quality of the GAT. I can't guarantee that you'll like them but you owe it to yourself to give them a try.
If you buy new Telefunkens elsewhere, make sure they are not the JJs labeled Telefunken currently being manufactured. I haven't compared them but I think most would agree the JJs are not Telefunken quality tubes.
Upscale Audio recently purchased a large quantity of brand new, never used NOS NIB (new in box) Telefunken E88CCs and is selling them for a very good price. I would strongly recommend that you try these in a preamp of the quality of the GAT. I can't guarantee that you'll like them but you owe it to yourself to give them a try.
If you buy new Telefunkens elsewhere, make sure they are not the JJs labeled Telefunken currently being manufactured. I haven't compared them but I think most would agree the JJs are not Telefunken quality tubes.