Wednesday, September 21, 2011

A review of the JJ ECC803S vacuum tube

This is the other 12AX7 tube made by JJ and it is very different both in sound quality and construction from the previously reviewed JJ ECC83 S tube, with its’ frame-grid construction and compact, 6DJ8-style plate structure. This ECC 803 S long-plate 12AX7 variant is a recreation of one of the finest vintage 12AX7 tubes, the Czechoslovakian-made Tesla ECC803S. It is rumored that Tesla actually made many tubes which eventually were labeled, boxed, and sold as German Telefunken, and the ECC803 S is a prime example of this often-discussed practice. Setting aside our discussion of the history and provenance of the JJ ECC803 S for a moment, the review panel took several minutes to physically examine our review specimens. Like the other JJ 12AX7 variant, the ECC83 S, this tube also has a very solid, “weighty” feel which conveys a sense of quality. In the transconductance tester, the two internal sections of the JJ ECC803 S were fairly well balanced with each other in all tubes evaluated; most varied less than 10% from triode one to triode two (the 12AX7 tube is actually two individual triode tubes combined in one glass bulb).

We then installed the tubes into the test phono stage - a EAR 834P - and prepared for our listening/evaluation session by cueing up one of the most well-recorded LPs available, “Drinkin’ TNT and Smokin’ Dynamite”, the legendary performance by Buddy Guy and Junior Wells at the Montreaux Jazz Festival. Because the Rolling Stones happened to be recording in a studio located very close to this venue, their bass guitarist Bill Wyman dropped in to play for the sessions captured here and issued by Blind Pig Records. This recording is very useful for evaluating not just tubes, but audio equipment, and phono cartridges as well because it features a well-defined sense of “space”; in other words the echo and decay present when listening to a live performance in person is captured very well here, as are the audience noises and other subtle spatial cues. With the very best 1950s and early 1960s NOS-type tubes such as the Raytheon 7729 and square getter, longplate Genuine British Original Mullard ECC83 from the legendary Blackburn, Lancashire Mullard factory, it is possible to hear individual audience members shouting praise and requests from the back of the hall in between songs on this reference quality, all-vacuum tube recording. Likewise, when Junior Wells draws down deep to belt out a phrase or classic line, the listener can hear the faint echo reverberate and decay with tremendous precision. The JJ ECC 803 S longplate tube did perhaps less well than hoped at capturing the small details of this extraordinary recording. The fundamental notes were reproduced accurately and with natural timbre, but the complex harmonic swirl and 3-D imaging that are the hallmarks of a truly great 12AX7 tube were perhaps slightly lacking here.

The JJ ECC803 S was indeed successful at presenting a balanced, “tube like”, musical soundstage that had some elements of soundstaging and imaging present... but it was most certainly not the best in the areas of resolution and detail retrieval.
Strengths—Good imaging, natural sonic balance, “tubelike” presentation that hinted at the sonic performance of classic NOS 12AX7s.
Weaknesses: Less than excellent detail retrieval and only medium resolution.

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


A review of the JJ ECC83S vacuum tube

The JJ ECC83 S is substantially different in construction from the other 12AX7 types considered here. The JJ tube is made with an advanced technique known as “frame-grid construction” first pioneered by Telefunken. Frame grid construction is most commonly associated with tubes such as the 6922 and 6DJ8, but is also employed by JJ with this tube.

Technical details aside, this Slovakian 12AX7 tube falls sonically at a midpoint between the Chinese 12AX7B and the Russian Sovtek 12AX7LPS. The listening panel found the main weakness of the JJ ECC83S to be a slightly lackluster level of resolution; it simply failed to capture many of the subtle nuances and micro details of our reference LPs. On the classic Ornette Coleman LP “This Is Our Music” the listener can occasionally hear the musicians take a particularly deep breath off-mike before a long run of notes. This and other subtle shadings were less well reproduced by the JJ than with either the Shuguang 12AX7B, or the Sovtek 12AX7LPS for that matter.

Listeners who primarily listen to rock and roll music will find the JJ more suitable; it has a sense of cohesion and balance that delivers much of the raw punch and metallic edge of AC/DC lead guitarist Angus Young’s opening salvos on their classic “Let There Be Rock” album. However, with any source material the JJ ECC 83 S maintained a consistent, “tube-like” sound characterized by a natural resolution of complex harmonic structure, good sonic balance from the lowest bass octaves to the surprisingly natural, extended treble response. Like the Shuguang 12AX7B, the JJ ECC 83 S produces a sonic image that is slightly less detailed and high-resolution than the ideal, but unlike the Sovtek LPS or the Tung Sol Russian 12AX7s, the JJ ECC83S never let the listening panel forget that they were hearing the magic of vacuum tube, analog audio.

Strengths—Natural sonic balance and presentation.

Weaknesses: Less than excellent detail retrieval and only medium resolution.

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


A review of the Tungsol 12AX7 vacuum tube

This 12AX7 tube, also made in Russia, features a much shorter plate structure than the Sovtek LPS 12AX7 made by the same manufacturer. It closely resembles current Electro-Harmonix 12AX7 tubes, but we are told by the distributor that it is made from premium materials and undergoes additional factory selection as compared to the Electrio-Harmonix to weed out any inferior examples.

We installed a set into an EAR 834P, and during the initial warm-up for the tubes selected an LP to begin the evaluation. We cued up a first pressing of the Steely Dan classic “Aja” and placed the stylus on track one. The original USA pressing of the “Aja” LP is extremely well known in the audiophile community as a “golden ear” record and indeed is a favorite of the review panel. We thus anticipated a strong rendition of the crisp, dynamic, and very much 3-dimensional recording. However, it was immediately apparent that the Tung Sol 12AX7 simply was not up to the challenge of retrieval and reproduction of the tremendously detailed and dynamic recorded sound present on the “Aja” LP.

Put simply, the Tung Sol is just not an engaging, musical 12AX7 tube. The bland soundscape presented by the Tung Sol is quite two dimensional in comparison to the Shuguang 12AX7B, and even made the slightly flat sonic image of the Sovtek 12AX7LPS seem rather deep by comparison. At this point we ceased all evaluation of the Tung Sol 12AX7 tube because it cannot be recommended for use.

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

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.


A review of the Shuguang 12AX7B vacuum tube

The Shuguang 12AX7B is a popular current-production vacuum tube from China that offers reasonably natural sound reproduction at a budget price. It is not perfect, but represents one the better currently available 12AX7 tubes. The Shuguang 12AX7B reproduced the bass, drums, and vocals of the classic Marvin Gaye LP “What’s Goin’ On”quite convincingly, laying down a strong bottom octave and lending vocals a warm, natural openness. The Shuguang 12AX7B’s warm, lively midrange also does well with Jazz and Classical music. Above the upper levels of its pleasant midrange, however, the 12AX7B from China begins to gradually roll off treble response. Brass instruments lose the leading edge of their fierce attack transients to a degree, and cymbals are reproduced mainly as the initial crash, with much less harmonic “shimmer” content resolved as compared to the Russian 12AX7s. The treble that IS there has a harmonic “rightness” to it, but much of it simply gets lost in the mix. And while the 12AX7B from China is not exactly ultra-high resolution it does produce an organic, natural-sounding soundscape. The Shuguang’s deficiencies are relatively easy to live with; this tube did not mangle or greatly alter any part of any recording we played using it, nor did it dry out or impart a “cold” presentation to well-recorded music.

Strengths: natural timbres which produce a harmonic rightness and midrange warmth, both of which make it the most natural sounding 12AX7 of the current production tubes.
Weaknesses: Does not have much upper treble extension, washes out some detail of great recordings.

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


Tuesday, September 20, 2011

A Visit with the B&K Pro-5 preamplifier

The interest in my hobbies wax and wane depending on what else I am doing with my busy schedule. Lately I have been writing, publishing, weightlifting and enjoying time at the beach. With the end of summer, I suddenly had the urge to mess with some audio gear. Since I needed a ‘backup’ to use in case my vintage Threshold FET-10/HL or Audio Research SP-7 preamplifier went down for repairs, I opted to buy a full-function unit. With a B&K ST-140 already in the stable, why not try a matching preamplifier? So I went and bought a B&K PRO-5 for $195 via Audiogon.

Upon arrival, I opened the box and was greeted by a nice looking unit. The gold lettering, handles, and black faceplate are conservative in an 80s kind of way. The back has a number of RCA jacks that appear to be of questionable quality – they look nickel-plated and are soldered directly to a rear-mounted PCB board. The selector switch has a nice solidity, but the other controls feel on the low-rent side.

Cracking open the case, I found the parts quality to be rather pedestrian. For example, the volume, balance, treble and bass pots are small carbon units that look like something you would find on a 1970s receiver. The power-supply is a joke with a tiny transformer, a pair of 1000uf capacitors, and a pair of 15V regulators. The phono stage uses a few capacitors, FETs or transistors, and some op-amps involved. The same is true of the linestage and tone-controls. There really is nothing here that screams AUDIOPHILE with big bold letters, but let’s see how the B&K PRO-5 sounds.

Removing the ARC SP-7 from my second system was easy enough. I then hooked up the turntable to the new preamp phono input and then connected the line outs to the ARC D-52B amplifier. I switched on the preamplifier and the front rocker light turned on with a pleasant glow. With my first record, I was greeted with sound alright, but the left channel was missing. I wiggled the back RCAs and *pop* I started getting sound out of both channels. Obviously these RCA jacks are going to be troublesome for long-term use.

As far as sound in active mode with the tone-controls bypassed, the B&K PRO-5 has a pleasant, slightly warm sound. Some treble detail is a little glossed over, but the bass is good and punchy. Overall depth and soundstage width is a little squashed, but this is certainly a better overall-sound than many other budget preamplifiers I have heard – which is quite surprising considering the lack-luster parts quality. But if there is anything that I have learned from this zany hobby - it’s that you have to trust your ears and not your eyes.

I mentioned the ‘active mode’. You see, the PRO-5 allows you to bypass the active linestage with a push of the button. In this passive mode, the gain understandably drops and you have to crank up the volume control to get the same output as before. But the sound, though less punchy, becomes more neutral. It’s almost like having two preamplifiers in one box. As far as what sounds better – that’s entirely up to your system and musical tastes. Perhaps it is the psychological effect of having to turn up the volume control so much, but I preferred the active linestage for most of my pop/rock music. With classical music CDs, the passive section was given the nod.

In overall quality - both sound and mechanical - the Audio Research SP-7 still wins. It is a little brighter and brasher in comparison, but the overall sound is more neutral. Of more importance - especially in a system that is heavily used by my family - the ARC has much more solid connectors plus a positive volume and selector-switch action.

Note - during my listening sessions with the B&K Pro-5, I found the RCA connections to be very problematic. Later versions apparently used better parts, but for owners of the older model, you are stuck with some very poor connectors. Replacing the RCA jacks with something sturdier looks like a difficult task, but I’m going to give it a try. So stay tuned for a future update.

Second System:
Preamplifier: Audio Research SP-7
Amplifier: Audio Research D-52B
Analog: Dual CS-5000 turntable - Audio-Technica AT95E cartridge
Digital: Pioneer DVD-V7400
Speakers: KEF iQ30
Speaker Cable: Canare 4S11 Quadlink
Interconnects: Cardas Crosslink