Saki,
The Shuguang Black Treasure 6CA7 is available in quantity from Rachel at Grant Fidelity. Likely about $300 per quad. Grant stands behind everything they sell. I also believe Trelja here, at Audiogon sells this tube. The RFT Siemens EL34 is harder to get and can be costly. I paid about $200 for a matched pair from Brent Jesse and $150 that matched well with the Jesse tubes from a friend.
I have also used the Mullards, very nice in 12ax7 position. I forgot to mention mention that I used the Gold Lion KT77s. Again, the Shuguang Black Treasure did it for me in both the Primaluna as well as my Coincident Dynamo 34SE. Best
The Shuguang Black Treasure 6CA7 is available in quantity from Rachel at Grant Fidelity. Likely about $300 per quad. Grant stands behind everything they sell. I also believe Trelja here, at Audiogon sells this tube. The RFT Siemens EL34 is harder to get and can be costly. I paid about $200 for a matched pair from Brent Jesse and $150 that matched well with the Jesse tubes from a friend.
I have also used the Mullards, very nice in 12ax7 position. I forgot to mention mention that I used the Gold Lion KT77s. Again, the Shuguang Black Treasure did it for me in both the Primaluna as well as my Coincident Dynamo 34SE. Best