November 27, 2012
The Amperex Pinched-Waist 6922 PQ has been and continues to be my favorite input tube for the conrad-johnson Premier 140 power amplifier. This particular tube was manufactured at the Hicksville, NY plant in November, 1958 (7LK *8K ) and was packaged the 14th week of 1959. The Amperex 6922 has the number “848” etched vertically at its top and this may indicate the tube was manufactured in the 48th week of 1958 but that’s only guesswork on my part.
This tube has the D-getter structure and the famous pinched-waist which may be seen as a narrowing of the glass bottle starting at the splatter shield and descending to almost the middle of the plate structure. It is thought that the narrowing was an attempt by the maker to minimize microphonics by more securely anchoring the tube’s innards. At least one online vendor (Upscale Audio) believes that this pinched-waist version of the tube tends to be noisy. Another vendor (Tube World) deems the 1958 Holland made version of this tube to be the best sounding 6922 ever. You pays your money and you takes your choice.
Unfortunately, it is the only one of its kind that I own, so I’ve only been able to use it in my power amp. I own two Amperex Bugle Boy 6DJ8/ECC88, also with the early D-getter structure. One was made in July, 1958 and the other in January, 1959 and they’re from the Heerlen, Holland plant. They are the earliest examples of this type that I have and may be the subject of a future review.
I’ve rolled this tube into the Premier 140 many times since its capacitors were upgraded to the CJD Teflon type. It’s been used in conjunction with many power tubes and with a variety of dual triodes in the Premier 16LS2 preamplifier. The Listening Impressions immediately below are a compilation of my thoughts on the Amperex Pinched-Waist 6922 PQ.
- May not have as much gain as the 6922EH.
- Treble is softer, not as piercing with less sharp transients but the leading edge/timbre/decay cycle is of one piece and, to use a cliché, has an organic quality that is approached by other dual triodes, but never matched.
- The antithesis of “hi-fi sounding” with vocals residing more in the throat and vibrato clearly defined.
- Extended at both frequency extremes.
- Upper bass and lower midrange is somewhat emphasized.
- Wind instruments have a breathy quality at times.
- Dynamic when the source material allows.
- The sound stage is transparent and subtly layered with each image spread across a wide, deep and tall acoustic space.
- Percussion is reproduced, in particular, in a natural, but never edgy fashion.
- Detail retrieval is reference level and changes in the system are immediately apparent.
- Grain-free with any texture heard originating in the recording or source component.
To sum it all up in three words: revealing, refined, musical.
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