I am trying to put together my impressions of the 5 different tubes I tried to audition. I have come to the conclusion that it is not a good idea to listen to two different tubes and A/B the channels using a good mono recording. The reasons are as follows:
a) If one tube plays louder than the other, psychologically you tend to give it preference. It is very hard to adjust the volume for the other channel to be equal as you switch from A to B.
b) If one tube is as day and one as night, meaning totally different, it is easy to pick a winner - "the difference is as day and night." But if the tubes are very similar, it becomes very difficult to pick the better one.
c) Some tubes are much better in the bass than others, others excel in the mid range, and others in the treble. How do you compare them to each other?
d) Even though the two channels in the Little Dot MKIII are completely independent, there may be a synergistic effect in playing two identical tubes. (In other words, the sum total is greater than the parts.) I have no scientific proof or sources for this, but nevertheless I think that this is the case.
So, with all these caveats, I am going to try to rank the five different tubes, but take these ratings with a grain of salt.
5) We will start with the loser: Tung Sol 6AV6 from the 50's-60's. Boomy bass, congested mid range, rolled off treble, lack of detail, dark. Maybe I got a bad sample; but I only have one tube. Anyhow, you remarked about these - at this stage I would not order them.
4) and 3) shared: Sylvania JAN 8532 from 1970. Detailed, powerful bass, goes lower than any other tube in this group. However, the sound is not full bodied but thin sounding.
Sylvania 6AV6 old side getter style. Good overall presentation, detailed, neutral with strong bass.
2) Sylvania-Phillips 6AV6 late 70's early 80's tube with a little ring attached to the plate: Very good and open presentation, bass not highly detailed but very good; rich treble, excellent overall.
1) The winner: RCA 6AV6; Lively, up front, open, detailed and airy presentation. The bass is not overly powerful and detailed, and the treble is too bright and has to be turned down, but this tube is very engaging and nice to listen to. Did I mention that it plays the loudest of this bunch?
Re the TS 6AH6WA tubes you ordered I think that you will be very pleased.
While I am writing this I am listening the a pair of RCA 6BY6 tubes which are cousins to the 6BE6. These are quite nice and very realistic.
Got some single tubes from a friend - 6DK6, 6BE6, 6AG5, 6AH6, 6AV6 and 6BY6. All are Sylvania except for the last one which is GE. Before I try these I am going to go back to my old favorites 6AH6 and 6AU6 and just enjoy the music - need a break from head ache inducing critical listening lol....