Wednesday, September 21, 2011

A review of the Sovtek 12AX7LPS vacuum tube

The Sovtek LPS is well known to audiophiles as a capable, sonically balanced modern production 12AX7. The Sovtek LPS is very different from the Shuguang 12AX7B; almost immediately into the listening evaluation for the Sovtek LPS, a notation was made that “this is a tube that can really deliver extended treble.” While playing select Charles Mingus pieces from a Mosiac Records box set compiling his 1960 recordings for Candid Records, we were struck by the crisp, shimmering cymbals and the strong, clean, initial attack of Ted Curson’s trumpet notes.

However, we soon felt that the Sovtek LPS was missing the mark somewhat, especially in the all-important qualities of balanced harmonics, lifelike sonics and sheer organic, natural musicality. Soundstaging and expected 3-D imaging with the Sovtek 12AX7LPS likewise were slightly flat and two dimensional. The sound was in no way lifeless or dull, it just did not sound natural to any of the panel members. The treble detail and extension was impressive, but again somewhat less than natural. One listener remarked that the Sovtek LPS almost sounded like a transistor or op amp cleverly disguised as a vacuum tube. However, it did indeed display ruler-flat, accurate frequency response and a much more detailed and extended treble response than the Shuguang 12AX7B. As impressive as the airy, detailed treble of the Sovtek LPS is, our listening panel found it to be a less musical, less natural-sounding 12AX7 than the Shuguang. The Sovtek LPS is precise, clean, and razor-sharp. One panel member noted that these subjective observations were made using a system that employs a pricey high-output moving coil phono cartridge that excels naturally in treble extension and detail. Another member of the panel gave it the slight edge over the Shuguang simply for its better high frequency response but the Shuguang is far better overall.

Strengths: High Resolution. Extended treble response. Flat overall frequency response.
Weaknesses: Somewhat two dimensional, dry musical presentation, not as warm or natural as the Shuguang 12AX7B. Less-than-stellar 3-D imaging and soundstaging. Not especially “tubelike”.

***** A 2nd Look At The Sovtek LPS*****
Even a brief search of the information available on the internet concerning the Sovtek 12AX7LPS tube indicates that this tube is extremely well-liked by audiophiles and indeed is considered the “best choice” among entry-level priced 12AX7 tubes. We initially found the Sovtek LPS 12AX7 quite dry, metallic, and sterile sounding; “flat as a pancake and cold as ice” was how one particularly HARSH comment from the review panel put it. To attempt to narrow the gap of public opinion and the findings of the 12AX7 review panel, several listeners agreed to take the Sovtek LPS for an extended “test drive” in a variety of tube equipment ranging from a vintage McIntosh tube preamp to a Quicksilver full-function. 4 of the 5 listeners noted a distinct improvement in the sonic performance of the Sovtek LPS 12AX7 after a week or two of listening for an hour or two per day.

The Sovtek 12AX7LPS reconsidered:
This time around, the extended, detailed treble response of the Sovtek 12AX7 LPS had lost some of its metallic edge during the extended burn-in period. What once seemed overly sharp and almost cutting now presented as high-resolution, detailed sound. We still find the Sovtek 12AX7LPS to be a somewhat flat or two-dimensional sounding tube... most importantly it still maintained a good measure of the “transistor in a bottle” sound that dominated during the initial evaluation. This too had mellowed significantly, though. In many ways, the Sovtek 12AX7LPS is, when given an extended burn-in, a superior 12AX7 to the Shuguang. The Shuguang, over a longer period of listening, seems simply TOO kind to badly recorded LPs, while not really resolving the finely-honed details of the best LPs. Your findings will of course vary, but the listening/evaluation panel can now give the Sovtek 12AX7 LPS a solid recommendation.

Note: This review is actually from a multi-listener session of new production vacuum tubes. Notes were summarized by my good friend Chris James.