Audio Research SP-10 6922 or 6DJ8

Thanks to both of you for your advice. My SP-10 MK 2 posessed the most perfect midrange phono reproduction I had ever heard.....until my phono (4) tubes went. They were big bottle 6dj8s marked with no name, except "made in USSR" The sound was big, lush, 3D bigtime! and no brightness. The plates on these tubes were extra wide. Tried the ARC preferred Sovtek 6922 and was astonished at how bad the sound had become. The line section tubes were also a bigger bottle tube marked AMPEREX, made in Poland, Anyone ever seen an Amperex made in Poland? Also wonderful sound. The Telefunken ECC88 is wonderful, but somewhat hyper/detailed and missing the ultimate vocal warmth of the old tube

Frap, the Tele ECC88 is a warm tube, I think you may have suffered a slow loss of resolution and bandwidth over the years, and are perhaps forgetting the sound of those original (supplied) tubes in your ARC. I agree that just before they departed this earth, they probably were very dark and in their own way, beautiful. An easy and inexpensive way to find if this sound is really what you want, is to buy some tubes at or near the lowest usable transconductance. A tube dealer would be selling you VERY used tubes and the price should be remarkably low. I suggest Telefunken, as the midrange is still beautiful, until it dies. I do agree with your comments about the Sovtek 6922, it sounds remarkably bad when compared to at least a dozen other possible candidates. You mention that the line section tubes "were" also bigger. Does that mean they were replaced at the same time? If so, you have two things going on at the same time that effect the SP10's tonal balance. Have you checked all the other tubes? If you are having to replace this many tubes in the output section, how about those in the power supply? If power supply tubes are bad, and you put in new 6922's, that would really provide a situation for poor sound.

The topic of tubes has been covered here many times, but to answer your question, the Russians have done a great job on some tube types and not well at all on others. Unfortunately, the tube you and I are discussing ( 6922 / 6DJ8 / 7308 ), has not seen quality manufacturing by anyone that can equal the best of the new old stock. There is a huge demand for this tube type, and the need grows every year. Perhaps a US importer or distributor will invest the money needed to get a break through in quality on this particular type. I suspect the Russians are currently building the best tube they can, given the budget, tools and materials they have to work with.

Any thoughts on tube selection (6922,6dj8, ecc88) for ARC SP9 mkII?