A quick note on Cardas Hexlink speaker wire

Not a formal review, since I'm using this wire in a bi-amp system:

As part of my recent bi-amp setup, I decided to finalize the wire selection.  For the bass panel of the Magnepan 1.6QRs, I went with a pair of Kimber 8PR speaker wire.  This classic can pass enough current to handle the big power of the Threshold amplifier.  For the treble section, I went with a used pair of Cardas Hexlink 5-C wire via Audiogon.  At one time Hexlink was the top of the Cardas line. 

As usual, I wasn't expecting much difference with changing speaker wires, but I sure was surprised.  The Hexlink has a big sound - warm and almost golden - that lets the music breathe with ease and power.  I certainly wouldn't call it uber-detailed or very transparent - but it sure is musical and very enjoyable for long-term listening sessions.  As usual, the Kimber did a great job with the bass - sound very detailed, speedy, and with no overhang.

I just love it when a system comes together.


preamp: Threshold FET-10/HL modified for bi-amping
phono preamp: Audio Sector Phono Stage
amplifiers: Threshold S/500 (bass) and Yaqin MC-10T (treble)
analog: VPI HW19 MkIII - Rega RB300 with Incognito wiring - modified Denon DL-103R
speakers: Magnepan 1.6/QR with Sound Anchor Stands
speaker cable: Kimber 8PR (bass) and Cardas Hexlink 5c (treble)
Interconnects: Cardas Cross, Canare Starquad (to bass amp), Cardas Quadlink 5C (to treble amp)

Bi-Amping the Magnepan 1.6QR speakers

When I bought the Yaqin amplifier, I was impressed by the fidelity.  But since it didn't have enough power to drive the Magnepans 1.6QRs, I considered selling it.  Instead, a friend of mine suggested that I bi-amp.  Since then this has been on my to-do list for the past couple of weeks, but I've been busy with some other pursuits. But I recently had some free time and finally gave this a spin. First of all, my Threshold FET-10/HL preamp only has one set of outputs. Since I wanted to roll off the bass for the treble amplifier, I took one of the tape outputs, added in an in-line capacitor (calculated at .02uf for the 20k input impedance of the treble amplifier), and essentially made another set of outputs by paralleling it with the standard line out.

The bass amplifier was a Threshold S/500 - a powerhouse that has long been one of my favorite amplifiers. This amplifier will run full-range into the bass panel, where the stock crossover is still doing its thing.

The treble amplifier is the ultra-budget 50WPC Yaqin MC-10T with a coupling capacitor upgrade, 1950s-era Tungsol 12AT7s for the input tubes, Mullard CV4024s for the phase-splitter, and real Mullard XF2 EL34s.   The volume pot allowed me to match levels (by ear) with the Threshold amp. Extra speaker and interconnect cabling for this was a mish-mash of wire from my junk drawer.

I was immediately struck by the increase in fidelity - since the bass is rolled-off for the tube amplifier, it never seemed to run out of power. The sound with the stock setup (Threshold amp) has always been very good, but now the combination is 'the best of both worlds' - the bass definition and control of a big SS amp with the extended/clean treble of tubes. The soundstaging also had a more 3-D effect.  There is also less grain and less apparent distortion, the music sounding less forced and breathing with a graceful easiness.

One of my good audiophile friend came over and we took the chance to do listen to several records - Donald Fagen - The Nightfly, Fleetwood Mac's s/t, Pink Floyd - Animals, some Creedence, etc etc - and bi-amping has been a major, almost mind-altering improvement. The amount of detail, depth and sheer musicality has been greatly expanded. I really didn't expect this level of fidelity from the change, but I can't imagine going back to a single amplifier. With the big SS power driving the bass panel and the (bass-limited) tube amp driving the tweeter, a very good system suddenly became great.

I'll have to do some more listening, cable swapping, and tweaking - but so far I like what I'm hearing, making me afraid to do any radical changes. In the future I would like to remove the passive crossovers of the Magnepan and use an active one instead.

preamp: Threshold FET-10/HL modified for bi-amping
phono preamp: Audio Sector Phono Stage
amplifier: Threshold S/500 (bass) and Yaqin MC-10T (treble)
analog: VPI HW19 MkIII - Rega RB300 with Incognito wiring - modified Denon DL-103R
speakers: Magnepan 1.6/QR with Sound Anchor Stands
speaker cable: Kimber 4PR/8PR Bi-wire with banana jacks
Interconnects: Cardas Cross and Cardas Quadlink 5C

Upgrading the Yaqin MC-10T tube amplifier

In my more budget system, the stock Yaqin MC-10T has proved itself to be a great performer. Honestly, I wasn't expecting much from this low-priced Chinese tube amplifier, and was shocked by the level of performance I was getting. But plugging the Yaqin into my main system, and I started to notice some minor problems.

The first thing, of course, is that 50Ws of tube power just isn't enough oomph to drive Magnepans. Sure, it's okay for low listening levels or baroque music, but once something like Pink Floyd is played at decent playback levels, the Yaqin starts to stumble - the overall sound gets compressed and the bass becomes really sloppy. My eventual plan is to bi-amp, using the mighty Threshold to drive the bass panel, while allowing (with a suitable crossover) the tube amplifier to drive the tweeter. In theory this combination should be a winner.

The second thing is the coupling capacitor quality. There is a bit of opaqueness and lack of detail that could be coming from the low-rent stock units. I've often been impressed by Chinese amplifier metalwork, but less so with the passive parts quality. Perhaps some improvement could be found here.

The third thing to consider is the tube quality. I may be in the minority here - the early 1990s Chinese KT88 fiasco of yore still lingers in my mind - but I've liked recent Shuguang tubes. They have a smoothness and musicality that betters some of the older Russian stuff, all while being fairly robust. But for all their strengths, I've generally found the old American and European 1950s-1960s stuff to be much better than anything new.

For the purposes of this article, I'll skip on the bi-amping and will instead concentrate on the coupling capacitor upgrades and tube rolling.

The most difficult part of the changing capacitors in the Yaqin amplifier is actually getting to them. Removing the top plate, you can see the circuit boards and transformers. The capacitors (both power and coupling) reside under the PCB. Gaining access requires removing a kajillion screws holding the standoffs to the bottom plate.

You will also have to snip out a few zip-strips and unplug a few wires to safely push the PCB on its side. Here you can see the larger .22uF/250V and the smaller .1uf/400V blue caps. Since I had some real Wima MKP caps on hand that fit perfectly, I went this route. I'll note that the Wimas - though good- are not exactly world class, but trust me, anything much larger is going to be impossible to fit in there. Space is at a premium and with the tight-fitting metal case, there is no room on top either.

After some soldering frustrations, I had everything back in place and ready to start rolling some tubes. But I first did a few hours of listening to determine the differences (if any) with the new caps. The change was fairly minimal with a slightly cleaner top-end and perhaps a touch more detail. Honestly, I would only go this route if you are so inclined and (very) handy with a soldering iron.

Next up was changing the stock Shuguang 12AT7 tubes. In theory this change should have the greatest effect on the sound. Since I don't have a large stash of this tube, I had to go shopping. Trolling hither and thither, I scored some 1950s-era Tungsol 12AT7s via Ebay, and bought a pair of Mullard CV4024 from Upscale Audio. With the Tungsol as the input tube, the Mullard used as drivers, and the stock Shuguang EL34s, I sat down and gave the Yaqin a listen.

This was a major improvement - listening to the 1975 Fleetwood Mac self-titled album brought further depth and instrument clarity.  For some reason, there seemed to be more apparent power too.  Treble detail increased dramatically, showing just how important the driver tubes are, even in a negative feedback amplifier.

I've often railed against the cost of vintage tubes - but in my experience, they've been the best. With a budget amplifier, it really doesn't make sense to spend a fortune on the 'good stuff', but I was curious to see how well the Yaqin would perform with something world-class. Enter in a set of real Mullard XF2s. Though these tubes already have many hours on them, they still test as new, and with the conservative operating points of the MC-10T, they should last for a very, very long time.

At first I thought the output tube change was minimal, but as the Mullards settled in to place, the sound just got better and better.  For example, listening to Steely Dan - The Nightfly, the female backing vocals took on an amazing separation.  Instead of a homogeneous blob, I could now hear the individual voices.  Instrument attack and dynamics also improved, easily besting the Shuguangs.  It isn't that the Chinese tubes were bad, it's just that the vintage Mullards were that much better, casting a bigger and deeper soundstage with a more realistic, less hi-fi presentation.

In the end, my appreciation for the Yaqin amplifier grew. I've owned many tube amps - most of the Dynaco line-up, Harmon-Kardons, Scotts, Heaths, Fishers, and my own DIY designs, and the Yaqin is right up there with some of the best ones.  Stock, out of the box, it's a screaming deal. With the right tubes and a coupling capacitor upgrade, they truly are great amplifiers

Next up is bi-amping. I initially intend to try a simple in-line capacitor to roll off the bass for the Yaqin. In theory this should give the amplifier for headroom since it won't have to handle the low frequencies. Another option is to use an active crossover, which can also be used to replace the passive components that are mounted within the speaker. This is ultimately the best route to go. Stay tuned!

Main System:
preamp: Threshold FET-10/HL
phono preamp: Audio Sector Phono Stage
amplifier: Threshold S/500
analog: VPI HW19 MkIII - Rega RB300 with Incognito wiring - modified Denon DL-103R
speakers: Magnepan 1.6/QR with Sound Anchor Stands
speaker cable: Kimber 4PR/8PR Bi-wire with banana jacks
Interconnects: Cardas Cross and Cardas Quadlink 5C

A Visit with the Yaqin MC-10T integrated amplifier

I have a love/hate relationship with tube amplifiers. Though I've rarely heard one that I haven't liked, they can also be troublesome little beasts. Much of that has to do with modern tube quality - the stuff coming out of China, Russia, and Slovak just doesn't compare to the days of yore when tube electronics was the only game in town. Back when I first got into tube audio, it was easy to buy a $100 Dynaco 70 that came with real Mullard EL34s. Now those tubes (and the amplifiers themselves) have become more and more expensive, making the hobby less and less fun. I'll admit that one of the reasons I recently jumped on the high-end solid-state bandwagon was to reduce my worries over quality tubes and the vintage amplifier high cost of entry.

But Yaqin - and other Asian tube amplifier makers - are starting to change my perception. Since I was impressed with the Yaqin MC-22B phono preamplifier, I decided to check out one of their amplifiers - the 50WPC Yaqin MC-10T integrated amplifier which can be had for under $500. For the price of a forty-year old used Dynaco 70, one can buy a brand-new unit with separate bias pots for each tube, a fine gold chrome finish and nice 5-way speaker jacks. It sounds almost too good to be true. Is it? Let's find out.

I bought a new Yaqin MC-10T from a stateside seller on Audiogon. Shipping was prompt and I soon had the heavy box in my hands. Packaging was excellent with heavy foam to protect the amplifier and plastic tubes to protect the vacuum tubes. The metalwork of the amplifier was very impressive - back in the 90s, I would have thought this was a $2000 unit. This particular amplifier uses a pair of EL34s and a pair of 12AT7s per side. Power supply rectification comes from solid-state diodes, though I would have ideally preferred dual 5AR4s. The power and output iron is your standard bog iron-core, covered by some large, but well-finished green cans. There is a 4-position selector switch for the line-level inputs (no phono preamplifier is included), a power switch and a volume control.


The manual, except for the technical section, is fairly worthless. It looks to have been translated from Chinese to English using an online translator, since the words used are unintentionally hilarious. But through the muddled English, I managed to figure out the suggest bias points.

Removing the Audio Research D-52B, I hooked the Yaqin up to give it a listen. I first checked the bias and found that it was off, even though it is supposedly set at the factory. I found the bias test points easy enough to use, but getting the allen wrench into the adjustment pots was difficult without burning your fingers against the closely positioned EL34 output tubes. After that was completed, I started to spin some CDs and records.

First up was Bob Dylan's Live 1975 - Volume 5 of the famed 'Bootleg Series'. This is one of my favorite live albums, even though it suffers from a minor 70s vibe. Through the Yaqin, I heard a very nice detailed sound. The crowd sounded live and energetic as they listened to Dylan play It's All Over Now, Baby Blue. For a CD of unreleased material, the sonics are pretty good.

Using the Audio Research SP-7 as a phono preamplifier, I then played OMD's Organisation, an album of melancholy synth music. Through the KEF iQ30 speakers, bass had a nice growl and the midrange was crystal clear with a nice and extended top-end. Next up was Icicle Works - The Small Price of a Bicycle. Though this album suffers from 80s solid-state production, the emotional impact of the music was evident as the powerful vocals soared straight into my heart.

Needless to say, I was very impressed with the Yaqin MC-10T. Though the bass lacked the ultimate control and deepness of the venerable Audio Research D-52B, the overall sonics were surprisingly refined and detailed. Soundstaging is deep and wide, and there is a coherence from top to bottom that doesn't suffer from any vintage tube amplifier sponginess. From memory alone, I would say the Yaqin bests my old modified Dynaco ST-70 and perhaps even my Dynaco Mark IIIs. At this price point, it's an amazing accomplishment and something that should keep American tube amplifier manufacturers awake at night. Very recommended, but with some caveats.

My issues with this amplifier just revolve around potential internal build quality issues and the possibility of troublesome Chinese tube sockets. In a future post, I'll delve deeper into the Yaqin MC-10T with some modifications. capacitor upgrades, and tube rolling. Stay tuned!


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

A Visit with the Yaqin MS-22B phono preamplifier

I first got into audio, way back in the mists of time, because of vacuum tubes. Thanks to hearing a friend's McIntosh MC240 and an old Dynaco PAS (both extensively modified), I heard music in such a way that forever changed the way I look at stereo equipment. Lately I've been dabbling in solid-state; trying to wring out whatever musicality I could from these silicon devices. And to a certain degree, really good SS gear can capture much of the magic of vacuum tube gear without the worry of tube life. However, vacuum tubes have a sheer musicality that is hard to replicate with solid-state. You can call it warmth, dimensionality, or liveliness - but there is something special about valves.

I've heard a number of positive reviews and experiences with the Yaqin MS-22B. This is a simple two-tube phonostage that uses a solid-state buffer. From the pictures, it looked impossibly well-made for only $179 shipped. I was curious enough to give this budget unit a chance, so I ordered one via Ebay. To my surprise, I had it in my hands in a week.

Pulling the Yaqin MS-22B out of the box, I was surprised by the heft. The metalwork also appears to be of a high quality, having lettering for the tube types, power switch and the RCA jacks. The stock tubes are Shuguang 12AX7Bs - known to be a little dark in their presentation - and are covered with twist-on metal shields. The input and output jacks, plus the ground lug are also very nice. The power transformer is mounted on top and is covered with a metal box that looks like a small toaster oven. I've built my own DIY phono preamplifiers, and I know from experience that building something like this from scratch would cost more than the Yaqin asking price.

Okay, how does it sound? Since I only have one turntable that uses a MM cartridge, I could only check out the Yaqin in my second system (listed below). Placing the 22-B on top of my Audio Research SP-7, I soon had the cables switched around. I then turned on the Yaqin, which emitted a nice blue glow through the front logo. Note - there was a nice thunk when powered on, so keep your volume control down when turning the 22-B on.

The first record on was Pete Townshend's classic Empty Glass. Through the Yaqin, the music had a nice bouncy rhythm, a surprisingly extended top-end (considering the Shuguang 12AX7Bs), deep bass, and a engaging character that made the record a joy to hear. I then went and cooked some dinner, leaving the Shuguang on to warm up further. After eating, my fellow audiophile friend came over. We listened to Frank Sinatra's Strangers in the Night and Neil Young's On the Beach, and concluded that the Yaqin MS-22B is one hell of a deal. At least in the confines of this budget system, we heard an extra dimensionality that the Audio Research did not have. The ARC SP-7 is definitely more neutral, detailed, and 'high-end', but the Yaqin was more engaging, musical, and just plain fun. At the price it is being sold, it is also a great bargain. For a budget system - highly recommended, but with some minor caveats.

What are my issues with this phono preamplifier? I did notice a bit of hum at higher volume settings, but this shouldn't be an issue unless you are running high-efficiency speakers or a lower output cartridge. I also found the bass to be a little plummy - perhaps this could be corrected with some tube rolling.


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

Modifying the Denon DL-103R phono cartridge

The Denon DL-103 is a popular low-output moving-coil phono cartridge that has seen a recent renaissance in the audiophile world. It's always been one heck of an audio bargain, so of course once the tweakers got a hold of it, things were bound to get a little crazy.

I bought the more expensive DL-103R, which features high-purity copper coils and a lower output impedance, which makes it perfect for my Audio Sector Phono Stage. I was really impressed by the sound of the 103R. but read numerous online suggestions for improving the sound. So with much trepidation, I went and bought an aftermarket aluminum body from an Ebay seller called sound-improvements.

Removing the original plastic body from the Denon takes a steady, steady hand. I really didn't want to do this operation, but it actually turned out better than I expected. While cutting out the glue in the corners, remember to keep the stylus protector on, which is the only way to protect the cantilever. Luckily someone posted a video on YouTube showing you how to take off the body:



When the body is off, you will end up with something that looks like this:


In order to get the nude Denon DL-103R to fit into the aluminum body, I had to round off the edges of the front plastic with a file. Then it was a matter of a dab of glue in the inside of the aluminum body before I gently slid the cartridge inside. I used the thin blade of my hobby razor to get it snugged in place.


After remounting, adjusting and resetting the balance (this cart is now HEAVY), I could finally give my Franken-cartridge a listen. Spinning some familiar records, I was impressed by the improved treble response. It now sounds more clear, less splashy, and with more apparent extension. The overall character of the Denon 'house sound' hasn't really changed, but it does now have a more 'proper' audiophile sound, removing much of the (minor) "rough 'n' ready" character of the old cartridge. These aren't really major changes, but just an increased level of finesse. Recommended, but only for those with nerves of steel.


System:
preamp: Threshold FET-10/HL
phono preamp: Audio Sector Phono Stage
amplifier: Threshold S/500
analog: VPI HW19 MkIII - Rega RB300 with Incognito wiring - Denon DL-103R
speakers: Magnepan 1.6/QR with Sound Anchor Stands
speaker cable: Kimber 4PR/8PR Bi-wire with banana jacks
Interconnects: Cardas Cross and Cardas Quadlink 5C

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.

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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.

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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 2^nd 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.

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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.

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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

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A Visit with the KEF iQ30 speakers

KEF was founded in 1961 by electrical engineer Raymond Cooke. KEF is known for several products, including the BB110 bass driver and T27 tweeter used in the famed LS3/5A broadcast monitor. Through the 70s and 80s, they pioneered the use of new materials and porting to speaker construction. 1988 saw the introduction of Uni-Q which became their signature driver. It’s a time-aligned coaxial driver using a neodymium tweeter where the dustcap is normally located. This unique construction allows KEF speakers to act like a true point-source and has excellent dispersion for listeners sitting off-axis. In the past, I’ve reviewed the vintage KEF C-75, Q30 and the Q60 speakers that first used the Uni-Q. I’ve always enjoyed these older speakers for their smooth midrange and coherent character. With a rounded treble and warm bass, their faults were always of omission– a perfect speaker for budget components and lower quality recordings.

When I decided to replace my Q60s with something that would better fit our latest decor, KEF immediately came to mind. So after some research, I purchased a pair of new iQ30 speakers from accessories4less.com for $399. The iQ30 is a bookshelf speaker that uses a 6.5” Uni-Q driver inside a curved cabinet to minimize internal reflections. Of interest is the tangerine phase plug which reminds me of something that Altec-Lansing used on their vintage horn drivers.

Since this is a small speaker, I also needed to buy a pair of speaker stands. I decided on a pair of VTI UF Series stands from Racks and Stands. Sitting at 24 inches tall. these stands can also be filled with sand to increase stability. Since I have cats and kids, I went this route.

So how does the iQ30 stack up against its older brethren? Let’s find out.

I received the iQ30s three days after placing my order. Packaging was excellent and the speakers arrived without a scratch. This is one great looking speaker with a modern shape and look that works well with the Ikea Expedit shelves I use to store my records. However I found the stock bi-wire links to be troublesome so I replaced these with 18awg bare wire. I then replaced the Q60s with the VTI stands before placing the iQ30 speakers on top.

Initial listening impressions were very impressive. For such a small speaker, the sound is quite dynamic and punchy. The lowest bass is pretty much non-existent which is to be expected for a 6.5" driver. However the upper bass is very good and with pop music, I certainly don't feel like I'm missing much at all compared to the 8" driver in the KEF Q60. For such a small speaker, the iQ30s sound bigger than I expected. I used to run a pair of vintage KEF Q30 tower speakers which also use a single 6.5" driver, but they sounded nothing like this modern iteration of the Uni-Q. In comparison, the iQ30s have more definition, speed, treble extension and detail. Extended listening smoothed out the slightly aggressive treble and increased the resolution even further.

Though the KEF iQ30s are surprisingly dynamic for their size, listeners of bass heavy music will be happier with a larger speaker or an added subwoofer. But for the price, the iQ30s punch way above their class; offering a taste of high-end audio that is highly addictive. Resolution is excellent as is soundstage depth and width. There is a coherency to the sound that reminds me of speakers costing much, much more. Highly recommended, but with caveats since they are limited in bass and will work better in smaller rooms.

Specifications:

Power rating: 15-120W
Input impedance: 8 ohms
Tweeter: 0.75" aluminum tweeter
Midrange: 6.5" bass driver
Crossover: 2.5kHz
Cabinet design: Bass-reflex, ported cabinet
Sensitivity: 89dB
Maximum output: 110dB
Frequency response: 45Hz - 40kHz
Dimensions: 8.7"W x 14.4"H x 12.9"D ea
Weight: 14.8 lbs ea

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 Q60

Speaker Cable: Canare 4S11 Quadlink
Interconnects: Cardas Crosslink

Update (03/26/13): It's rare for me to keep any audio component for so long, but the KEF iQ30 is a good looking and very competent performer.  I recently swapped them for the Spica TC-50s, using the KEF speakers in my main system.  I was very impressed - they handled bass and dynamics better than the Spicas, all while having a much more coherent sound.  With the improved front end and Eico amplifiers, they really do punch higher than their price suggests.  So now the Spicas reside in the second system while the KEFs stay with my more expensive setup.  In the future I would like to explore some more KEF products - perhaps the LS50 or Q300 monitors.

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