TAI has added three pieces of the excellent K&K gear to our inventory, a triode-converted amplifier, a tube headphone amp / control front end, and a tube phono stage.  K&K tube components use current sources (CS) and regulation, which flatten tube curves, slash distortion, and increase drive.  Of all available single-stage amplification, triodes are already lowest in distortion but supporting them with the CS drops this already low level through the floor.  The sound is powerful, dynamic, and decidedly un-tubelike.  A nice addition for the work we’ve been doing lately on a half dozen new speaker models, and more than resolving enough to reveal what they’re doing during design.  (The main The Audio Insider site is here, where we feature Swan, Dana, and other brands.)

The K&K ST70-based amplifier converted to ~15w triode output.

The K&K amplifier starts life as a common Dyna ST-70, the ubiquitous 35w/ch EL34 amp from the Sixties (be sure to read K&K’s take on this design).  Ours kept only a pair of mint condition output transformers – designed by David Hafler, expertly wound on grain-oriented steel, and very good, as it turns out – which were rebuilt with Teflon-and-silver wire leads, new powder-coated end bells, and stainless hardware.

New chassis, rebuild output transformers, and new power transformer.

A new 300ma high-current PA060 power transformer from Ned at Triode Electronics supplies current.  A new nickel-plated chassis houses the parts.  The real star of the show is the K&K differential input stage and driver, a very modern circuit using special Lundahl amorphous input transformers (I opted to use K&K’s top Premium series for all three new components, and all use the upgraded amorphous Lundahl transformers.)

The K&K Premium input / driver board with tube CS and Lundahl amorphous transformers.

I also converted the K&K ST70 from the amp’s original EL34 pentodes to 6B4 triodes.  Since the EL34 runs at over 400v in the original design, a few modifications were needed to adapt the circuit to the 6B4′s, which want a B+ rail of 250v.  I retained the original tube rectification, plugged in a new Mullard GZ33 rectifier, and I also converted the power supply, using the voltage drop of individual inductors per channel (there are four altogether) to get the Sovtek output tubes down to 350v.  While still 100v high, the Sovteks are actually closer to the WE 300b than the classic 6B4 and run fine at the higher B+.  Quiescent current is set through the CS to 50ma per tube, which through a CLC filter makes even the big power transformer run warm.

New-old-stock Mullard GZ34 rectifier.

Heavy-duty Sovtek 6B4 output triodes.

Russian ex-military dual triode signal tubes, one per channel.

Input stage adjustable Current Sources (CS).

While the amp is customized, The K&K phono stage is closer to its original circuit, having been modified only in the power supply.  There I installed two pieces of vintage NOS iron, the first being a potted ITC power transformer, and the second being a potted UTC choke to filter the B+ supply.  The supply is thus L-C, which offers the best passive regulation.  With such a large input L, the power supply’s turn-on time constant (K&K use a relay to energize the active circuit when the PS is up to speed) has moved up to about 30 seconds.  A NOS Sylvania 6C4 does the rectification.

The K&K Premium Phono Preamplifier.

One phono channel showing Russian dual triode, CS, and on the PCB behind them, adjustable MC input loading and Lundahl amorphous step-up transformer location. 

Phono preamp back panel.  Adjustable MC loading and optional balanced outputs.

 

Phono preamp’s custom power supply, finished in a vintage-look green hammertone.

The final piece is the K&K Differential Line Stage board, left stock but populated with PIO output caps bypassed with Teflon-and-foil caps, and joining signal switching, attenuation, and system power from a modified new Quicksilver chassis (thanks to Mike Sanders.)  I use this amplifier to drive dynamic headphones like the Sennheiser 600, which serve as one of my references. The power supply for this component uses a NOS Chicago Standard power transformer fed by a potted isolation transformer, and the back-panel switched outlet I plug the phono preamplifier into is fed by another isolation transformer.

 K&K line preamp / headphone amp built on Quicksilver preamp chassis.  Solid copper ground planes and subchassis, dual K&K shunt attenuators, and point-to-point OFHC copper and solid silver wiring throughout.

The use of a very highly modified ST70 as one of our test amps for speaker development was a calculated move – more on the just what can be done when both the electronics and speakers are bona-fide ultra-resolution when we reveal the new Dana models later in 2009.  Watch this space for a series of three articles on the new Danas…and how they sound driven by the K&K superstars.

While typically a 15w amplifier would be doubted in such a setting, especially when development moves beyond 2-way monitors, the K&K strategy paid off.  This amplifier can energize a large room through 88dB speakers, and in the nearfield we’ve even gotten near physical levels out of the ~85dB Swan D2.1se.  The advantage such an amplifier has is near-instantaneous overload recovery, something big consumer amps lack.

 One of the system’s eight Lundahl amorphous-core transformers.

The use of current sources and Lundahl amorphous transformers has revolutionized this very basic amplifier and turned it into a reference tool that sounds just as wide band and powerful as any good 50w transistor amp I’ve used over the past 25 years.  This assortment of equipment has removed the veils of conventional transistor amps and yet has the sheer speed, extension, micro- and macro-dynamics that not only belie that power comes from a moderately-sized tube amplifier, but turns on its head any doubts about transformer-coupled tube amplifiers.

The Lundahl amorphous core transformers used throughout are a revelation.  This is ultra-fi resolution and a deeply engaging, spacious, vivid sounding amplifier, as are all the K&K pieces.  The sound is tremendously detailed and “wideband”, yet organic and faithful to the recordings.  For a little less risk of transistor artificiality, I prefer tube rectification where possible, and while the push-pull circuit’s lack of 2nd order harmonic distortion removes the usual tube sound, the complete lack of grain says that this isn’t solid state we’re listening to.  The system actually sounds “faster” than that, owing to that grain-free presentation and such rapid recovery from big passages.  The system is challenging, to be sure, as it is quite ruthless to recordings, but it’s this quality that makes it such a valuable tool, at least until more power is called for.

Thanks are due to Kevin Carter at K&K.  This year we’re turning out a number of what I think will be seen as affordable reference-class speaker designs and we couldn’t have done it without Kevin and K&K.

Initial stocks of the interesting Swan D2.1SE have been depleted and we’re awaiting a series of shipments that will keep us stocked through the holidays. Frankly, I’ll admit that we underestimated the demand and we’re scrambling to acquire more samples.

So, maybe this is a good time to explain a little more about this model. The D2.1SE is a sounding board for a short tale about smaller speakers and musical faithfulness.

In the TAI forum I once mentioned a late friend, Jan Waalkes of West Michigan, where I’m from. Jan and I went back to about 1980 and I have to credit this audiophile’s audiophile with influencing me by wringing more music from any hundred dollar bill then probably anyone I’ve known, before or since. While Jan didn’t skimp where he felt he shouldn’t, he perpetually got so much musical truth from any particular combo of front end, electronics, and speakers that he was a force of one in local circles.

The last project Jan and I worked on together was voicing a 6.5” two-way system based on Danish drivers of the day, circa 1985, a design tradition that continues today involving prestigious brands all over the high-end landscape. I wish we had the parts then that we have available today.

I’ll omit the finer points, but in short Jan and I dialed the speaker in over the course of over a year – actually, he did the initial heavy lifting as it was his rig, but I still recall the day our crossover adjustments, working in roughly 1/3 dB increments, took this system from hifi speaker to, well, music. The system, for all the obvious flaws all systems have, simply went “over the threshold” and we both stopped hearing gear and started hearing recordings. Bands. Halls. Music.

It was an impossible sound, really. It was a bigger sound that the humble sum of those parts could be expected to deliver, but there it was. It was addictive and in the twenty-plus years since, I’ve only heard elements of that sound exceeded twice.

I think there are rare moments when audio transcends it’s physical origins and lifts you out of the chair. This speaker had that ability, even as conservative as it was at the time.

The trick was twofold: Whatever it is that these driver types do that’s so special combined with razor’s-edge tuning the dividing networks. Get it close and it’s a rich, nuanced, organic sound. Get it perfect and it’s kinda not a speaker anymore. It conflicts the listener. It defines the greatly over-used “jaw-dropping” euphemism. It stops being a loudspeaker, if that makes sense, and becomes a window on the outdoors — on the musical event. It does acoustical things you can’t really accept that an electromechanical system can. Disbelief is suspended.

This sounds odd – odd enough that I hesitate to post this, wondering if I’ll make sense to anyone who hasn’t heard it — but once you have heard it, you know what it is. I wondered ever since if I’d find it again.

Fast forward to the late Nineties and the HiVi/Swan D6.8 midbass driver. Excellent build quality, all the right parts, and a new, optimized, hybrid motor. Interesting – like old times interesting. Then, the HiVi/Swan run at 28mm domes. Also interesting – and an idea hatches.

Time passes and projects come and go and then, after what seems too long, the inevitable finally occurs: Rumors emerge of HiVi engineers merging the D6.8 7” midbass and the new Q1 28mm dome tweeter into a classic ported two-way stand monitor. Of course, we stand back, wondering how they’ll execute it.

Then a photo shoot occurs.

So we order twenty pairs and turn on the bench, expecting to run the measurements.

But they’re really good right out of the box.

Oh sure, not so “perfect” I wouldn’t want to play with the design when I have the time and when the market can add a few dozen percent to the D2.1SE’s current sub-$1,000 price, but so close that they hit that musical, organic, dimensional sound that tells me they got it very right.

After nearly a quarter century, my good friends from halfway around the world gave me a very big smile with the design brief itself, and then in actually putting the D2.1SE together as well as they have.

I’m not going to say a lot more about this speaker. Sure, we sell them and sure, we want you to buy them. But I really just want to relate one of those rare occasions when something special comes full circle and like an old friend — in this case very much like an old friend and an audio brother, rest his soulful ears – it’s like no time has passed at all. I’m pleased not only at just how happy twenty new owners are, but too just how timeless one of the better ideas can be.

This won’t be the end of this story, either. While it’s not our style to pre-announce models, we’re going to take the risk this once and state that we’re currently investigating just how far we can take this concept in terms of models added to the D2.1SE family. We’re not going to talk about the specifics until we have samples in-hand, but when that day comes, I think we’ll be announcing a little brother satellite and a pair of center channel models. From there, perhaps some floorstanders and matching subs – the HiVI/Swan 12” version of the D6.8 midbass is simply superb.

That’s enough for now – advance notes will appear here so consider this page your Swan bulletin board. I expect a very interesting Fall 2007 and Winter 2008 and if TAI can bring musical joy to another few dozen or even a hundred music-lovers, well, that’s what it’s all about, isn’t it? I suspect that’d make Jan smile too.

And Jan? If you can hear this, I didn’t forget. I dedicate this post and our efforts to your legacy.

Anybody have an idea what the world’s longest loudspeaker is? And where it’s located?

The answer is six hundred fifty feet, or two hundred meters! That’s the length of the planar-magnetic linesource array my dear friends from SONUS in Badan-baden Germany installed in the German Parliment building at the restoration of the former Reichstag. The Reichstag (from the German Reich and Tag) has its roots, as I understand it, in the Roman Empire.

SONUS’s Martin and Joachim fabricated this state-of-the-art monster overhead array composed of segments of planar magnetic drive elements made for them by BGC of Carson City, where I was based from ’94 thorough ’99.

These guys are the James Bonds of ultra-fi commercial audio. More about them and their amazing European adventures as the blog matures. I’ll have to blog from their office the next time I visit.