Tube types

@jond  thank you, that's great. Appreciate your help. 

Here ya go!
The 6DJ8 is a dual triode preamp tube. ECC88 is the European designation for this tube. 6922 and its European equivalent E88CC are premium versions of the 6DJ8. 7308 and E188CC and the CCa are super premium versions.  

@yogiboy  thank you. I wasn't aware of the CCa version. I see they're expensive! 

You may find these interesting: https://www.head-fi.org/threads/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes.761078/ and: https://wallofsound.ca/audioreviews/vacuum-tube-shootout-6dj8-types-part-1/ Keep in mind; there are a plethora of variables(individual tastes/biases/aural acuity, speaker system response/accuracy, electronics, etc) ie: Read Paulo’s post(Wall of Sound site), with which I’d have to agree, 100%(far as audio equipment comments).

@rodman99999  thank you. I'll certainly take a look. I guess tube rolling could potentially be rather expensive in order to find the best combination 

Have you guys found that switching to premium tubes has been a significant improvement?