by petercapo » Fri Apr 29, 2016 9:14 pm
I thus far feel that the baseline character of my Stereo 70 (newer build, but original circuit topology) can have some emphasis in the bass region. And, to bring out more of the highs, I need to pick the right tubes.
Of the two choices you are considering, I have read a couple of different sources indicating that the JJ 6CA7 may be on the warm side with a pronounced bottom end. If this is true, then I would not think it would be a good choice for a stock Stereo 70 if you are looking for a more balanced sound top-to-bottom. The question of JJ reliability is a consideration, as well.
My impression from reading other comments is that the EH 6CA7 is less like a “typical” EL34, and sounds more lively and clear, and, I think, with more top end, all of which would be better for a stock Stereo 70.
In my experience, the EH EL34 also is lively with more top end than other EL34s, though not as overall refined as other EL34s. A good choice, IMO.
I have tried the reissue Mullard EL34, which I feel is a good choice, though it is not as lively as the EH and has a moderately extended top end and a less prominent bottom end.
One surprise I had recently was when I tried the Tung Sol EL34B. I read a lot of positive comments about it. But, I have not found it to be a good choice for my Stereo 70. To me, it sounds congested, too laid-back overall, the top end is too recessed and the imaging/soundstage tanked. Maybe this is a good tube in other amps, but it doesn’t work for me in my Stereo 70.
The overall best current production tube I have thus far tried is the Gold Lion KT77, though I hate to admit it because IMO it’s overpriced.
You know, I’d really address the red-plating thing further. It can have different, sometimes intermittent causes, and if the problem is not stabilized you’ll keep wrecking good tubes.