I'm Freaked Out by this Tube comparison

I was comparing two amplifiers - ARC VT100 Mk II & SF Power 2. They both have Sovtek 6922's in the input stage that were manufacturer selected and matched of about the same vintage. Both have 8 new EH 6550's, matched & measured.

On cymbals, brushes etc, the Power 2 had a more distant and smaller presentation that lacked detail. Chesky guitar recordings sounded thinner, had less ring, less body, less resonance. Overall, less involving sound.

I attributed the sonics to the design of the amplifiers. I had a third set of Sovtek 6922's that I put in the Power 2. No noticeable difference.

THEN ------ I decided to take the 6922's out of the VT100 & put them in the Power 2. I couldn't believe my ears -- now the Power 2 took on much, though not all, of the character of the VT100. The cymbals, etc. became more detailed, more present, more resonant. So did the Chesky guitars, and now with more body and resonance. More decay. In some respects, the Power 2 sounds better than the VT100.

Am I crazy??? I can't believe that one set of the Sovteks could be that much better than the other. Or is Audio Research's claimed intensive selection process responsible?

There is no biasing for the 6922's in the Power 2. SF told me to replace tubes, you just plug and play. The output tubes (6550s) were accurately biased in both amps.

What gives here?
Interesting story Kevziek. I do not think your nuts but stick around tubes long enough and you will be (Just kidding).

I am not a 6922 user at this time so I am a little out of the loop but I've heard there are a handful (up to 8 or 9?)different Sovtek 6922s that are not always easy to identify. Lots of mislabeling and lazy matching going on too. Maybe they are not as close to same vintage as you were told? Maybe you had a mismatch or a poor tube. I guess that's why places like vintagetubeservice.com/page4.html and tubeman.com , vacuumtubevalley, spend so much time testing pairs and matching. It's almost impossible to know based on what you said. There is a reported very basic difference between old and new Sovtek 6922s but I guess that doesn't surprise either of us.

It's hard to believe that "identical" tubes can sound different but it may be a little like speaker drivers. I have a little more experience measuring that stuff. They might all come out of the same factory but are all a little different when you measure them and the mfg's specs can almost never be depended on and then they take on a life of their own when you make them part of a specific circuit and enclosure. If you want a nice sounding pair you have to hand match and it's not hard to make a mistake.

Thanks for the story

I remain,
ARC provides a select group of 6922s that are tested for the specs to match the amp and for low noise and microphonics. I have heard a big difference in 6922s, based on where they come from.

I decided not to use ARC 6922s once in my VT-100. Never again. I will use other equivalents in NOS tubes, but if it is todays MFG tubes, go to ARC. I heard from a reputable source that ARC is rejecting 50%+ 6922s in the inspection process. I am not going to try my odds for $200 price difference for 8 tubes when a bad 6922 tube installed in a VT-100 can take out resistors and output tubes.

I am not affiliated to anyone -- just my experience and 2 cents. Kevziek -- you are not crazy, I have had the same experience.
I don't doubt your experience in the least. Welcome to the variables of tubes. I was trying to discuss this same thing in another thread, so you might want to take a look at it also. Sean

I don't use 6922's, but I have heard differences like are described here - just not between tubes of the same new manufacture and vintage (some can be noisier, more microphonic, etc., but the basic character is similar). Where I have heard these differences is between new tubes of unlike manufacture or vintage, so I would have to assume that the tubes described above are not really identical, despite outward appearances. I do know this: When I have bought "tested" tubes direct from conrad-johnson (who also claims a high rejection ratio and carefully controlled burn-in), I have found the results less than satisfying, and have had to go back and exchange certain tubes multiple times before giving up on them (and their higher prices) and just doing all the selecting myself by ear. Also, I would think that Sonic Frontiers, who sells tubes through their Parts Connection catalog, would have to have some sort of testing and QA program in place as well, and I for one would be surprised if any of these manufacturers' testing programs were that much better or worse than their peers'. Rather than placing faith in one company's pre-selected tubes other another's, I think it just boils down to the particular tubes in question in any given instance - one just has to listen for one's self, and if you're lucky enough to find a batch that sound better, then that's what you go with that time out. Next time, you may find you have to start the proccess all over again. Now, explain to me again, Why don't transistor users have ever-growing stocks of rejected and stand-by input and output devices cluttering up their closets, or have to pay return shipping charges on the losers, or run all over town searching for fresh ammunition for comparisions, or constantly wonder whether the sound has subtley degraded over time? Oh yeah, I almost forgot - They don't understand what *real music* should sound like. At least they have the time to listen!
I did make a slight error. The Sovteks in the VT100 are not of the same year as the other sets. The other sets are stamped 98-12 & 99-01. The VT100 tubes have no date, but the lettering and internal construction are identical. They are AR sourced, in since amp was manufactured (1997). So, my feeling is that either they are so critically measured & chosen, that they sound better. Or, the manufacture of the tubes varies that much.

I have some older (1996) Sovtek's where the construction looks different. Plus some unmarked ones that I think originated from Kevin Deal. I'll try these and let you know my results.

The amp was made in 1997
Kev- I have been told that Sovtek is just a generic term chosen for export to the West and that there were (are?) many different manufacturers. If that is true, take that and add that to the other variables, and what you report is not at all surprising.
Swampwalker, Sovtek is a brand made for New Sensor Corporation of USA. The owner was in business twice. He came into bad times in the mid 1980's, closed shop, then he started New Sensor several years later. The tubes are made in Russia by, I believe, Reflektor Factory, a large tube manufacturer. I don't believe they were always made there, especially back in the 80's. Someone correct me if I'm wrong.

Back to my tubes, all the 6922's I compared were made by the same factory and are the same design. If you look at them all, they are identical. That's the part that boggles my mind.
Welcome to the world of tubes. A manufacturer makes tubes, to pass electrical tests. A vender, such as Ram, New Sensor, Audio Research, etc., tests tubes, to meet certain electrical parameters. Certain venders, burn in tubes, so that the ones, that will fail early, will fail in burnin and will not wind up, in someones gear. Then they are tested again, and graded. 99% of the time, the customer, is the first to actually listen to music, through the tube. No manufacturer today, comes anywhere near, the consistency of manufacture, that companies had, during the tube making heyday. Different runs, off the same line, on the same day, will sound different. Every tube maker today, makes a great sounding tube. Its just that they have problems, consistently making a great sounding tube. No manufacturer, is going to destroy tubes that test great, just because they don't sound great. A tube that tests perfect, does not neccessarily, have to sound perfect.
Did you try putting the 6922 from your SF into your ARC amp, and did the sound of your ARC change? I'm curious as the ARC's sensitivity to a change in input tubes.
The VT100 has very complicated adjustments for the 6922's, so placing other 6922's in it is not the best idea. I'm afraid of blowing a resistor. My guess is that if the adjustments are so critical, just throwing some other tubes in there will result in worse sonics.
Any other Power 2 owners who experimented with 6922s out there?
I am in the market for a new amp and the ARC VT100 is one of the amps I like. Is it that much better sounding than the Power2? What qualities are better on the ARC? I am seeing some pretty good deals on Power 2s out there and am just wondering if I should buy one.
Meby, I'm still sorting out the two amps sonics. The ARC has more definition in the high end, but sounds a little lighter overall. Power 2 a little fuller, voices sound weightier, but some of the clarity is gone. Both sound good, but neither is perfect.