This may be sacrilegious, but I've found over the years the variance for me between "like" and "don't' like" between NOS and current production tubes, at least for the 12AX7 family of tubes, is no greater than the variance
among NOS tubes.
I'm currently using a combination: NOS Mullard 4024 (12AT7) in the input section of my Jolida 1701 Hybrid Integrated amp, and Tungsol reissue 12AX7 in the tube output of my Jolida JD100 CD player. 12AX7 tubes are standard with both units, and I've tried numerous combinations of the series (12AX7, 12AT7, 12AU7, 5751) using NOS Sylvania (JAN and JHS), GE, RCA, RFT, as well as new production Gold Lions, Tungsol, EH, JJ. Speakers are Omega Super 3S (with Cardas binding posts). Interconnects are Darwin Silver. Power cords and speaker cables are Cullen Cable Crossover Series.
I can hear every change, subtle and pronounced, amongst the tubes (Thanks Louis!). I can't honestly say every signature, regardless if the tube was NOS or current production, was the cat's meow. Each has strengths and weaknesses which can be emphasized or deemphasized using the whole audio system....and according to one's taste. For example, the Mullard 4024 midrange is outstanding, which I've found common with most Mullard tubes. They also tend to be a bit softer on top, to my ears. I don't know if it's because the mids are more pronounced and/or rich, or the top end is actually rolled off. The Gold Lion 12AX7 midrange is also outstanding and, oddly enough, both different and similar to the Mullards. The Gold Lions sounded more balanced on top and bottom, which may have affected the way I heard the mids. Plus, they have different output levels separate from their sonic signatures. To complicate things further, they
both sounded different when I swapped them between components! The Tungsol 12AX7 reissue images just like a NOS Sylvania 5751 (very holographic in my system)...but only in the Jolida CDP! Is it because, imaging-wise, it's as good as the Sylvania (in the CDP), or is it because (like earlier) of the 12AX7's higher output versus the 5751 and just the perception of better imaging? If I'm looking for imaging would it matter, particularly at 1/2 or 1/3 the price? If lowering or raising the output level (interchanging 12XXX and 5751 tubes) affects a components signature the same as swapping in/out NOS or current production tubes...should it matter? And what are the other sonic trade-offs? Food for thought
The combinations and examples are endless. To further complicate things, I heard strengths and weakness in tubes (both NOS and new production) thrown out the window simply with a power cord change. A JJ tube with a thick midrange now sounded open when a copper power cord was swapped with a silver-plated copper cord (same gauge). A RFT tube that imaged and detailed like crazy, but seemed to lack a little bass and warmth, sounded fuller and deeper with a power cord that had UPOCC connectors ( and larger gauge conductors). Of course, the cords didn't change the tubes...they simply powered the component. But they did make the
system sound like a tube was swapped with a tube (NOS or new) that exhibited the
same trait when used with the
same and/or different components!
I've rambled, and could have just said YMMV regarding NOS tubes
But there are quality examples of both! I think quality components and cabling have a huge impact as well
