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Product Review - Diva Classic 100 Pro Tube Preamplifier - April, 2001

Paul Knutson


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Diva Classic 100 Pro Preamplifier 

Input Options: Standard Model has 1 Input for Best Possible Sound (no switches), With Option for Maximum 3 Inputs at $80 Per Additional Input.

Gain: 16 dB

MFR: 5 Hz - 38 kHz

Maximum Output: 15 VRMS

Input Impedance: 80 k Ohms

Output Impedance:  1.2 k Ohms

Tube Options: KR10 or 6SN7 Depending on Model

MSRP: $1480 with KR10 / $1280 with 6SN7


Diva: Marketed by THE SOUL OF MUSIC, 1 Coleman Street, #03-46 The Adelphi, Singapore 179803; Phone/Fax: (65) 33 777 15; E-mail: seahss@singnet.com.sg; Web: http://web.singnet.com.sg/~seahss/soul.html  

Introduction

I wanted to write some type of humorous or anecdotal opening to this review, but I soon realized that a lot of fluff isnít necessary to get the point across.  Itís the same with the Diva Classic 100 Pro linestage preamp Ė thereís no fluff there, either.  Its circuit is purposefully simple and pure.  Those attributes are among the design goals that I hold in most high regard when it comes to building preamps.   The Divaís simplicity and purity of design help it achieve a place among the best affordable tube preamps of which Iím aware.  That, my friends, is the real take-away point from this opening.

Iím not a circuit designer, and frankly, many complex schematics scare me, but I can follow instructions to the "T" and have built a couple of kit preamps in my day.  (This is ironic because as a male I possess that innate avoidance mechanism when it comes to following any type of written assembly instructions, as evidenced by the towel cart in our bathroom that three years since ďassemblyĒ still doesnít have those roller feet installed.)  What Iíve learned from building kit preamps is that itís possible to create a true high performance linestage tube preamp by using a minimum of parts and utilizing straightforward circuit design and layout.  The Divaís talented designer, T.S. Lim, apparently sees things similarly.

The Diva

The Diva line of audio electronics, which includes other preamplifier models, power amplifiers, and cable, is designed and built in Singapore.  The aforementioned T.S. Lim is the designer/builder, while Richard Seah of The Soul of Music is the distributor who works closely with Lim during trade shows and similar events to promote Divaís products.  Not a bad job to have, Iíll bet.

The Diva preamp model that I listened to for this review was the Classic 100 Pro, with an optional tube upgrade to the KR Enterprise KR10 tube.  The upgrade package retails for $1,480.  The standard Classic 100 Pro is the same circuit, but instead of the KR10, it utilizes a single 6SN7 dual triode (more on that tube shortly) for voltage amplification.  That setup retails for $1,280. The inside of the chassis is shown below, and you can see that the tube is mounted horizontally. Look how simple the circuit is. This is one big reason tube products sound so good. There is not a lot of stuff in the signal path.

The Classic 100 Pro is a two-box affair, with a separate, outboard regulated tube power supply featuring a single GZ32, the American tube designation equivalent is the 5U4 rectifier tube.  In fact, the 5U4, along with the 5R4 and 5AR4, can be substituted. The power supply has a standard IEC power cord receptacle, into which I plugged an HSRi powercord from TG Audio for most of my listening.  The umbilical cord from the power supply to the control box is detachable, thin, and very flexible, like many members of the Ukrainian womenís Olympic gymnastics team.  The only power switch for the preamp is located on the front panel of the power supply (see photo below).

The main control unit of the Diva is all business Ė on it youíll find no bells, whistles, or other such adornment.  There is one pair of single-ended RCA type input jacks on the back panel, and one stereo volume control knob on the front, plus a small LED to indicate power. Thatís it.  I told you it was simple.  Diva does offer an option of adding two additional pairs of left/right RCA inputs, at $80 per additional pair.  To be sure I was listening only to the circuit, and not to the sound of a selector switch, my review sample was requested with just one pair of inputs for the ultimate in circuit purity. A photo of the rear panel is shown below.

The Classic 100 Pro looks good overall, with nice fit-'n-finish, but its appearance isnít going to fool any of your audio buddies into thinking that it costs as much as a new Kia.  Itís well-known that the cost of the chassis typically drives overall production costs, so for the Divaís $1,480 you can expect nice wrappings, but not something that would be right at home in the Museum of Modern Art. You are paying only for function with this product.

KR10 vs. 6SN7

I mentioned earlier that the Diva Classic 100 Pro comes standard with a 6SN7 for voltage gain duty.  This medium-mu, dual-triode tube is truly my favorite small signal tube.  Many fantastic examples of this tube were produced in the 1940ís, and when it comes to tube-rolling, thereís really nothing like sampling different 6SN7ís.  Iíve got a nice collection, and I was looking forward to hearing how they compared in the Diva.  In fact, the use of the 6SN7 was one of the reasons I was originally interested in the Diva preamp. It runs hot but is very linear.

As we arranged for the review sample, however, Richard Seah was so enthusiastic about Divaís top-of-the-line Classic 100 Pro, featuring the rather new KR10 input/driver tube, that we agreed Iíd have a listen to that version instead of the 6SN7 version.  I must admit to feeling a tinge of disappointment, but the KR10 is intriguing enough that I quickly got over it.  The KR10 handles more power than a 6SN7, and it requires more filament current, but otherwise theyíre electrically similar.  Some in the audio press had even referred to the KR10 as a ď6SN7 on steroidsĒ, a marketing pitch I wasnít entirely sold on.

Whatever my preconceived feelings were on the KR10 tube, a listen was certainly in order.

The KR10 is also a medium-mu (moderate gain) dual-triode, but itís much beefier than a normal 6SN7.  Check out the picture above, and youíll see what I mean (KR10 on left, 6SN7 on right).  The KR10 tube used in the preamp has been modified, so that it now has a pin structure that is identical to that of the 6SN7. This means that KR10 tubes and 6SN7 tubes can be interchanged in the Diva preamp, although we should recognize that they have different operating parameters, and therefore, the preamp can really only be optimized for one tube or the other, unless some type of switch is installed.  Plus, thereís no tube rolling (trying out a collection of tubes from various years) with any vintage KR10ís, because there arenít any.  The KR10 is a new tube, and itís unique in its design.  There are no NOS (New Old Stock, meaning old tubes that have never been used) tube substitutes or equivalents of which Iím aware.

Because the KR10 is a dual-triode, just one tube amplifies both the left and right channels.  This is a good thing, because re-tubing the Classic 100 Pro with the KR10 would be a bit too dear if you had to spring for more than one KR10.  The KR10 retails for approximately $200 each, roughly four times the cost of a top-notch 6SN7.  I would not recommend that you worry much about re-tubing, however, because the KR10 should last 10,000 hours or more.  Unless you listen to your system 24/7, youíll enjoy a heckuvaí long time between tube replacements.

Comparing and Listening

As has been the case for some time, I use a passive preamp from Monolithic Sound in my reference system.  I do so because itís absolutely a reviewerís best friend Ė a passive tells no lies!  Moreover, the Monolithic PA-1 is simply a wonderful performer and a killer bargain to boot.

Truth be told, however, I often yearn for the richer, warmer, and meatier sound of a good tube preamp.  Sure, I could fulfill that yearning in a heartbeat by choosing a nice tube preamp as my reference, but Iíve found that there is a greater chance of variability with regard to how tube preamps interact with other components Iím reviewing.  The Monolithic simply allows me to be more sure that what Iím hearing is the component under review, and not an electrical interaction aberration.  Therefore, I use the passive preamp as my everyday reference.  But, donít think for a minute that I donít appreciate a good tube preamp when I hear one.

The Diva sounded like it continued to improve through about 80 hours of break in.  That tells me that either it had some run-in time at the factory, or itís a bit quicker to settle in than most other tube preamps.  Set-up was a non-event because of the unitís simplicity.  There really is nothing you need to know, other than it does like a good power cord on the power supply.  I also preferred the way it sounded with Vibrapod isolators (four of the #1 pods) under the main control unit, but experimentation is always recommended when it comes to isolation devices of any type.  Also, if setup permits, I highly recommend that you keep the power supply away from the main control unit Ė youíll be rewarded with a blacker sonic background.

When I began listening critically (yes, I also note the irony that at some point reviewers have to stop listening for fun and start listening to be critical), what I first noticed on familiar recordings was that vocalists or mid-range instruments seemed to expand and occupy more space in the performance area.  The effect was not overly-exaggerated, but compared to what I was used to, it was unmistakable.  Chalk one up under the category of ďWhat Tube Preamps Sound LikeĒ.   Far from being a drawback, this aspect of the Divaís presentation was entirely pleasant on most naturally recorded material.  It gave an aural illusion of greater weight and body.  Where it wasnít so welcome was on heavier rock, and complex, dense orchestral pieces where the extra mid-band presence wasnít needed.

The Classic 100 exhibited a legion of wonderful sonic qualities, most notably an unmistakable tonal richness and a plethora of color and contrast.  Those are the characteristics that very good tube preamps do well, and the Diva is no exception.  Compared to other budget tube preamps that have occupied lots of time in my system, notably the Wright WLA12A and Audible Illusions 2D, the Classic sounded more substantial, with better drive and a greater perceived ability to hit all the notes and slam out all the beats.

Whenever a component excels in displaying that sense of liveliness, and energy, showing authoritative, yet tuneful low bass, I want to attribute it to a well-designed power supply.  When a component comes across as shy, and perhaps a bit anemic at propelling music forward, I want to attribute it to a crummy power supply.  In both instances, Iíll bet Iím right 90% of the time.  How this relates to the Diva is that I believe the power supply is very good Ė not perfect, but certainly very good.  A practical litmus test for this on my system is how a component handles the Revelation disc by Cyrus Chestnut (Atlantic Jazz 82518-2).  This wonderful and simple recording is characterized by some amazing dynamic contrasts that present a challenge to any power supply.  In the case of the Diva, I was not disappointed by the result.  It turned in a strong performance, comparable to or better than other preamps in its class that Iíve had in my system.  Comparing the Diva to more expensive preamps, like the Bruce Moore Companion II in Jason Serinus' system, the Diva demonstrates less vividness, life and contrast, but thatís only noticeable in a head-to-head comparison with a really excellent preamp that goes for about $3,500.

The Classic was cohesive and unified, as demonstrated by the way that it presented music as music, rather than a set of distinct but interrelated sounds.  Compared to my own Monolithic Sound preamp and Jason's BM Companion II, however, it was not quite as organic and natural.  When listening to solo classical guitar for instance (something I find myself doing a lot of lately Ė try the Lorenzo Micheli recital on Naxos 8.554831 and prepare to be impressed), there was some sense of a truncated ďpluck, pluck, pluckĒ on the strings rather than hearing the pick snapping the string, followed by an eruption of the primary tone, then the dispersion of overtones and undertones, and finally decay.  Granted, that all happens very quickly when someone is playing guitar, and I exaggerate the description of what happens to make my point more lucid, but what I described is easy to hear and itís also what a guitar sounds like in real life.  Iím not sure to what I should attribute this aspect of the Classicís performance, but I suspect the culprit is the use of a small amount of negative feedback in the circuitís amplification stage.  Negative feedback often manifests itself audibly by conveying a mechanical rigidity and lack of musical flow.  Negative feedback in a circuit gives you better measured specs, but Iím not so sure itís great to listen to.

No type of music was left untouched in evaluating the Diva, and it handled all genres competently. When listening to passionate chamber music and other natural acoustic recordings, I felt that the Diva simply shone.  When things got more complex, as with quartet (or more) jazz groups, the Diva managed to sort out these multiple instrument recordings with a near-perfect balance of clarity and warmth.  The individuality of performers was not lost in the translation by passing through the Diva en route to my power amp(s).  If you want to hear something that the Diva reproduced really well, and which also happens to be a smashingly good recording of a group whose music successfully combines elements of rock, blues, and jazz into one fantastic album, pick up a copy of Four Feet High by the Seattle-based band Soup of the Day (House of Pain Productions 9455-6).  I imagine that, in heaven, all rock albums are recorded this naturally.

I somewhat preferred the Classicís rendering of instruments as opposed to voices, but only slightly so.  Where the ďsoundĒ of the Diva worked against it was with deeper male voices, like Mighty Sam McLain, or John Martyn, and some of the heartier female voices, like Ella or Sarah, or even Patricia.  As I mentioned earlier, the Diva imparted a bit of a sonic ďauraĒ around such voices, puffing them up and bringing them slightly forward in the soundstage compared to how those same recordings were handled by my reference preamp.  The effect just described was not as noticeable with lighter, more breathy vocalists, male or female.  The Diva also contributed an extremely slight sense of diffusion to voices, which subtracted from the illusion of intimacy with the vocalist, but it didnít necessarily decrease the realism.  This isnít an egregious coloration by any means, and itís exposed only in direct comparison to my passive reference preamp, which to my ears is scott-free of any identifiable colorations.

Bringing it All Together

Iím loathe to dissect a sub-$1,500 preamp by how it handles every piece of the sonic spectrum.  I doubt that the target market for the Diva is comprised of those who relish audiophile sonic spectaculars and other such tomfoolery.  Personally, Iím not particularly interested in listening to a group of my geographic ancestors play dixieland-jazz in a junk shop, and I doubt that potential Diva buyers are either.  Besides, what the Classic does well is play real music, in a way that relaxes you, allowing you to be immersed in the beauty of it all.

However, to minimize flame mail, I will say that, yes, the Diva is well-balanced from top to bottom.  It does low and mid-bass admirably, not remarkably well, but very competently.  I was not disheartened by the Divaís performance on the Beastie Boysí ďShake Your RumpĒ off of Paulís Boutique (Capital 7 91743 2).  Iíd have been bummed if the Diva would have failed to pound out that songís way-down bass lines, but it held its own.  Up top, the Diva isnít closed down in the highs like some poorly designed tube preamps can be.  There isnít quite the purity and extension way up there that my Monolithic Sound preamp exhibits, but few tube preamps pass a signal like a passive when it comes to the upper register.  To the Divaís extreme credit, I felt that it was marginally clearer and more realistic in the highs than the previously mentioned Bruce Moore Companion II preamp in my friendís reference system.

The sub-$1,500 tube preamp market is competitive, but not exactly bristling with activity.  Iíd love to hear more examples in this category to place the Diva in better perspective.  Iíve discussed preamp pricing before, so you know that I feel $1,500 gets you most of the way there.  The price curve bends sharply upward after that point while the increase in performance curve bends gently like the shoreline of a very long beach.

Conclusion

The Divaís strongest suits can be summed up by the fact that it truly sounds like a good tube preamp should sound, and thatís high praise indeed.  You are also getting a unique product with the Classic 100 Pro because, to my knowledge, itís the only commercial design available that utilizes the KR10 tube.  Based on what I heard, that tube is competitive with the upper echelon of vintage 6SN7ís, yet it has the advantage of being in current production, whereas the best vintage 6SN7ís are currently made of unobtainium.

It goes without saying that the Diva Classic 100 Pro isnít the last word in high end preamps.  It isnít supposed to be.  But for everything it does well, and thatís a long list by any measure, I suggest that you hear the Diva if you are in the market for a preamp that you can really afford, and that you can enjoy listening to without reservation.

Who says there are no more Divas?

 

- Paul Knutson - 

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© Copyright 2001 Secrets of Home Theater & High Fidelity
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